Patent Publication Number: US-9898026-B2

Title: Power distribution apparatus with input and output power sensing and method of use

Description:
CROSS-REFERENCE 
     This application is a divisional of U.S. patent application Ser. No. 12/824,059, filed 25 Jun. 2010, now U.S. Pat. No. 8,305,737, tided POWER DISTRIBUTION APPARATUS WITH INPUT AND OUTPUT POWER SENSING AND METHOD OF USE, which is a non-provisional of U.S. Application Ser. No. 61/220,542, filed 25 Jun. 2009, titled POWER DISTRIBUTION APPARATUS WITH INPUT AND/OR OUTPUT POWER SENSING, AND METHODS OF USE, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure is directed to power distribution systems and technologies, and in certain more particular applications to a power distribution system for distributing power in a rack or cabinet environment and having a capability to monitor one or more power related metrics. 
     BACKGROUND 
     Power monitoring and metering have long been used in some applications to provide any of a number of items of information to different entities that supply, deliver, and consume power. One common use of such information may be used to determine energy consumption for purposes of billing a user for the power received by that user. One area that is continuing to increase in the amount of power consumption is related to computing facilities that are continuing to house more and more equipment, often referred to as server farms or data centers. Such facilities often have numerous individual pieces of computing equipment that are arranged in racks. Power distribution units have long been utilized to supply power to electronic equipment in such facilities (as well as racks and equipment in many other facilities as well). A conventional power-distribution unit (PDU) is an assembly of multiple electrical “outlets” (also called “receptacles”) that receive electrical power from a source and distribute the electrical power via the outlets to one or more separate pieces of electronic having respective power cords plugged into respective outlets of the PDU. PDUs can also have power cords hard wired to a power source instead of, or in addition to, outlets. PDUs can be used in any of various applications and settings such as, for example, in or on electronic equipment racks, among other applications. A PDU located in a cabinet may be connected to other PDUs or to other devices such as environmental monitors, for example temperature and humidity sensors, fuse modules, communications modules, and the like. Such a PDU and any other PDUs and other devices to which it is connected are commonly enclosed within an equipment rack or equipment cabinet and may be collectively referred to as a Cabinet Power Distribution Unit (CDU). 
     As mentioned, computing facilities generally include electronic equipment racks, such as standard RETMA racks, that commonly comprise rectangular or box-shaped housings sometimes referred to as a cabinet or a rack and associated components for mounting equipment, associated communications cables, and associated power distribution cables. Electronic equipment is commonly mountable in such racks so that the various electronic devices are aligned vertically one on top of the other in the rack. Often, multiple such racks are oriented side-by-side, with each containing numerous electronic components and having substantial quantities of associated component wiring located both within and outside of the area occupied by the racks. Such racks commonly support equipment that is used in a computing network for an enterprise, referred to as an enterprise network. 
     In many cases, computing facilities such as server farms or data centers support large networks, referred to as enterprise networks. Enterprise networks exist to support large world-wide organizations and depend on a combination of technologies, e.g., data communications, inter-networking equipment (frame relay controllers, asynchronous transfer mode (ATM) switches, routers, integrated services digital network (ISDN) controllers, application servers), and network management application software. Such enterprise networks can be used to support a large company&#39;s branch offices or campuses throughout the world, and, as such, these networks have become mission critical to the functioning of such organizations. Masses of information are routinely expected to be exchanged, and such information exchanges are necessary to carry on the daily business of modern organizations. For example, some international banks have thousands of branch offices placed throughout Europe, Asia and North America that each critically depend on their ability to communicate banking transactions quickly and efficiently with one another and with their respective headquarters. 
     A typical enterprise network uses building blocks of router and frame relay network appliances mounted in equipment racks. Such equipment racks are distributed to remote point of presence (POP) locations in the particular network. Each equipment rack can include frame relay controllers, routers, ISDN controllers, servers and modems, etc., each of which are connected to one or more power sources. The value of POP equipment is often very substantial, and the number of individual devices can exceed several thousand. 
     As mentioned, a relatively large number of equipment racks are commonly located in one or more data centers, and may act as hubs for data communications for an enterprise. Additionally, an increasingly common practice is for multiple enterprises to use a computing facility for all or a part of the enterprise computing requirements, such as through the use of a co-location facility. Conventional network management technologies provide relatively little information related to electrical power consumption in a data center or to status of a data center and of equipment racks within such a data center and of components associated with such equipment racks. Energy consumption of data centers can be a source of significant costs for an enterprise, and increasing energy efficiency of data centers could provide a significant cost savings for an enterprise. Furthermore, the ability to accurately measure power provided to identified racks and components within a data center can enable the operator of a data center to accurately bill costs associated with a particular rack or component. 
     SUMMARY OF CERTAIN ASPECTS 
     In various embodiments, systems and methods are provided that sense and output information related to the current and voltage that are present at the power input(s) to a PDU/CDU. The current and voltage information may be used to provide a number of measurements, referred to as power metrics. In some embodiments, these metrics may include one or more among aggregate power consumed components that receive power from the PDU/CDU and power consumed by the PDU/CDU itself, power factor, crest factor, true RMS current and voltage measurements, active power, apparent power, and energy consumption. 
     One or more such, or other, metrics may be used for any of a number of purposes, among them one or more of the following:
         analysis and actions that enhance the efficiency of an enterprise network, a data center, and components in the data center;   providing information related to managing assets in a computing network;   accurately tracking and billing energy used by assets;   identifying components that are receiving or providing power in an anomalous manner indicative of an actual or potential malfunction;   locating a server that has become comatose (not doing anything useful); and   identifying cabinets that are underutilized. A user may elect to idle all components in an underutilized cabinet and any associated cooling equipment as well, cutting energy usage.       

     Some embodiments of the present disclosure may provide, alone or in combination, one or more advantages over traditional PDUs. In certain embodiments, a PDU can have capability to measure and report various metrics related to power that is supplied to one or more power in-feeds to a PDU and one or more power outputs from the PDU. Such power metrics may be used to determine one or more efficiency calculations to identify efficiency of power usage in a data center, for example. 
     In some embodiments, power metrics may also be used to provide information for particular groups of equipment, particular cabinets, particular groups of cabinets, and the like. Such information may be used for evaluating equipment configurations, billing for power usage, providing trend information, and providing power efficiency information, to name but a few examples. 
     Some embodiments of the disclosure may provide a relatively accurate energy accumulation scheme for one or more inputs associated with a single power monitoring and metering circuit. Certain embodiments may sample voltage and current, such as at an ADC for example, for an AC cycle, and in this regard in some embodiments both voltage and current are sampled nearly simultaneously for an output. 
     In some embodiments, the product of each of the samples can be summed over the AC cycle. An AC cycle may be sampled at a known frequency, such as once every 24 cycles for a particular power output. Such sampled cycles may be scaled and accumulated over a time period to provide an accurate energy measurement (watt-hours) for each input. 
     Some embodiments may provide an accurate energy accumulation scheme for one or more inputs and one or more outputs. Certain embodiments sample voltage and current from both the input(s) and output(s), such as at an ADC for example, for an AC cycle, and in this regard in some embodiments both voltage and current are sampled nearly simultaneously for an output. In some embodiments, the product of each of the samples can be summed over the AC cycle. An AC cycle may be sampled at a known frequency, such as once every 24 cycles for a particular power output. Such sampled cycles may be scaled and accumulated over a time period to provide an accurate energy measurement (watt-hours) for each input and output. Providing input power information in conjunction with power information for each output of a PDU may provide additional information related to the efficiency of a system, and may provide power information for a group of equipment receiving power from a PDU with enhanced accuracy as compared to simply summing power from each output. 
     Some embodiments may have switched output capabilities and if desired provide output switching at or near power zero-crossings in the AC power cycle or at least likely below the a power peak in the AC power cycle. In some embodiments, for example, the AC waveforms provided to an output are sampled and at or near the point of current and voltage zero-crossings, outputs may be switched at or near zero-crossings. In embodiments that use relays for switching outputs, such at or near zero-crossing switching can be, in some applications, less stressful on the relay and the relay points. In certain applications, this may result in increased component lifetime and reduced in-rush current into the component that receives power from the respective output to possibly also reduce stress on that component. 
     Some embodiments of the disclosure provide a modular construction of an outlet assembly with options to provide one or more of: (a) input power monitoring capability; (b) output power monitoring capability; and (c) switched outputs or non-switched outputs. In some embodiments, also provided is a PDU with the ability to determine if lack of power at an outlet is the result of loss of input power or a blown fuse. 
     In some embodiments, the systems may identify when a power distribution unit, has abnormal current or voltage characteristics. Such identification may provide an indication of a potential failure of some component associated with the PDU. In some embodiments, current and voltage information are collected for a PDU and compared against model or historical information. In the event that an anomalous event is detected, a message may be transmitted indicating the same such that an investigation or corrective action may be taken. 
     In some embodiments, information provided by PDUs/CDUs may be used by an organization to take action such as, for example, corrective action, improving the efficiency of operations, providing power metrics for specific cabinets or groups of cabinets, providing more accurate billing for energy usage, and identifying equipment that may be a candidate for consolidating operations. In some embodiments, corrective action may be taken such as in the event that a CDU/PDU generates a warning that the current or voltage waveforms of, for example, a power supply have a significant deviation from a historical or model waveform. In some embodiments, such deviations may indicate the power supply is malfunctioning and corrective action can be taken. In some embodiments, power metrics may be used to evaluate the operation of items of equipment and groups of equipment to identify areas where efficiency can be enhanced, for example. Similarly, power metrics may be used to determine energy usage, and provide billing for separate entities that use a data center, for example. 
     It is to be understood that the foregoing is a brief description of some aspects of some exemplary embodiments. It is therefore also to be understood that the scope of the invention is to be determined by the claims as issued and not by whether given subject matter includes any or all such aspects, features, or advantages or addresses any or all of the issues noted in this Summary or the Background above. 
     In addition, there are other advantages and varying novel features and aspects of differing embodiments. The foregoing and other features and advantages will become more apparent from the following detailed description, which proceeds with reference to the accompanying figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a conceptual depiction of power needs in a computing facility. 
         FIG. 2  is a block diagram of an embodiment of a power distribution unit. 
         FIG. 3  is a front view of a CDU. 
         FIG. 4  is a block diagram of power reporting components. 
         FIG. 5  is a schematic diagram of an outlet circuit. 
         FIG. 6  is a schematic diagram of a relay circuit. 
         FIG. 7  is a schematic diagram of a current sense circuit. 
         FIG. 8  is a schematic diagram of a voltage sense circuit. 
         FIG. 9  is a schematic diagram of a power sensor and control circuit. 
         FIG. 10  is a block diagram of a microcontroller configuration. 
         FIG. 11  is a flow chart depicting operational steps of a microcontroller. 
         FIG. 12  is a perspective view of components mounted on parallel circuit boards. 
         FIG. 13  is a perspective view of components mounted on a circuit board. 
         FIG. 14  is a block diagram of a power management system. 
         FIG. 15  is a schematic diagram of a power monitoring circuit. 
         FIG. 16  is a block diagram of an embodiment of a power distribution unit. 
         FIG. 17  is a block diagram of an input power sensor. 
         FIG. 18  is a schematic diagram of a delta configuration. 
         FIG. 19  is a schematic diagram of a wye configuration. 
         FIG. 20  is schematic diagram of a three-branch configuration. 
         FIG. 21  is a schematic diagram of a dual power cord configuration. 
         FIG. 22  is a schematic diagram of a dual power cord, multiple branch configuration. 
         FIGS. 23-25  are a schematic diagram of a power monitoring circuit. 
         FIG. 26  is a depiction of an environment in which the invention may be practiced. 
         FIG. 27  is a flow chart of a method of managing electrical power usage. 
         FIG. 28  is a block diagram of a computing system in which embodiments can be implemented. 
         FIG. 29  is a block diagram of a computer network. 
         FIGS. 1A-75A  are screen shots and perspective views showing various aspects of embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Several embodiments including the preferred embodiments and currently known best mode of the present invention are shown in the following description and accompanying drawings. Exemplary embodiments of power distribution, monitoring, and management systems are described herein. Embodiments of such systems include a power distribution plugstrip, power distribution unit (PDU), and cabinet distribution unit (CDU) with power determination and monitoring capability. The present disclosure provides exemplary embodiments with capability to determine the power being delivered to a power distribution apparatus, and to determine the power being delivered from the power distribution apparatus to one or more electrical loads can enable efficient determination of power usage for various different components that are associated with a facility, and therefore provide ability to manage power to the various different components. In many cases, numerous PDUs and CDUs may be located in a facility, with each supplying power to several different electrical loads. Knowledge of power being delivered to various equipment in a facility may be used to evaluate, improve, and manage power consumption in a facility and across multiple facilities, such as data centers. 
     Such management of power may improve efficiency of power consumption at data centers as measured by one or more power usage metrics. One available measure of power usage efficiency for data centers is provided through metrics known as Power Usage Effectiveness (PUE) and Data Center Efficiency (DCIE). Such metrics enable data center operators to estimate the energy efficiency of their data centers, compare the results against other data centers, and determine if any energy efficiency improvements may be desirable. 
     Data center power and cooling are two significant issues facing IT organizations, and many entities desire to control these costs while enabling future expansion. With more energy efficient data centers, enterprises and IT organizations can better manage increased computing, network, and storage demands, lower energy costs, and reduce total cost of ownership (TCO). 
     As mentioned above, metrics may be used to determine information related to data center power usage, including PUE and DCIE. Both of these metrics provide a relationship between equipment power and total facility power. Total facility power is used to refer to the total power that is consumed by a data center. In the event that a data center is housed in a building that houses other functions addition to a data center or that houses more than one data center, the total facility power is the power that is used by the data center that is of interest rather than the power consumed by other uses than the data center of interest.  FIG. 1  illustrates computing equipment that may contribute to total facility power. The PUE is defined as follows:
 
PUE=(Total Facility Power)/(Computing Equipment Power)
 
The DCIE is the reciprocal of the PUE, and is defines as follows:
 
DCIE=(Computing Equipment Power)/(Total Facility Power)
 
     With continuing reference to  FIG. 1 , the computing equipment power is the power required to operate the data center equipment that is used to manage, process, store and route data within a data center. This includes the load associated with equipment, such as computer, storage. and network equipment, along with supplemental equipment such as KVM switches, monitors, and workstations used to monitor or otherwise control the data center. Total facility power is used to refer to everything that supports the data center equipment load such as power delivery components, cooling system components, computer nodes, network nodes, and storage nodes, and other component loads such as data center lighting and other ancillary equipment. Power delivery components include various components, such as UPS, switch gear, generators, PDUs, batteries, and distribution losses external to the IT equipment. Cooling system components can also include various components such as chillers, computer room air conditioning units (CRACs), direct expansion air handler (DX) units, pumps, and cooling towers. 
     The PUE and DCIE metrics provide a way to determine opportunities to improve data center operational efficiency, how a particular data center compares with other data centers, and opportunities to repurpose energy for additional computing equipment, to name but a few. While both of these metrics are related, they can be used to illustrate the energy allocation in a data center differently. For example, if a PUE is determined to be 3.0, this indicates that the data center demand is three times greater than the energy necessary to power the computing equipment located within the data center. In addition, the ratio can be used as a multiplier for calculating the real impact of power demands. For example, if a server demands 500 watts and the PUE for the datacenter is 3.0, then the power from the utility grid needed to deliver 500 watts to the server is 1500 watts. The DCIE, in comparison, may provide a different aspect of this information, a DCIE value of 0.33 (equivalent to a PUE of 3.0) suggesting that the computing equipment consumes 33% of the power in the data center. As will be readily observed, PUE can range from 1.0 to infinity, with a PUE value of 1.0 indicating 100% efficiency (i.e., all power used by computing equipment only), and a large PUE indicating that computing equipment uses a relatively small amount of the total power entering the data center. 
     In  FIG. 1 , total facility power is measured at or near the facility utility meter(s) to accurately reflect the power entering the data center. This represents the total power (for which the utility charges) consumed in the data center. In order to obtain accurate and meaningful power information, the data center power is either measured or otherwise calculated because power not intended to be consumed in the data center would result in inaccurate PUE and DCIE metrics. For example, if a data center resides in an office building, total power drawn from the utility will be the sum of the total facility power for the data center and the total power consumed by the non-data center offices. In some situations, the total facility power for a particular data center is required to be estimated or measured in another manner than through a utility power meter. Computing equipment power should be measured after all power conversion, switching, and conditioning is completed, and before the computing equipment itself, in order to gain meaningful information. In various embodiments disclosed herein, power delivered to computing equipment is measured at the output of the computer room power distribution units (PDUs). 
     Within a data center, it also may be desirable to measure data center performance. One metric that may be used to measure data center performance is referred to as Data Center Performance Efficiency (DCPE). The DCPE is defined as:
 
DCPE=(Useful Work)/(Total Facility Power)
 
This metric effectively defines the data center as a box and a net amount of useful work is done by the box.
 
     Additionally, additional granularity may be desired related to power usage within a data center. For example, a PUE metric may be broken down into the following: PUE=Cooling Load Factor (CLF)+Power-Load Factor (PLF)+1.0. All factors are ratios that are divided by the computing equipment load and 1.0 represents the normalized computing equipment load. Cooling Load Factor (CLF) is the total power consumed by chillers, cooling towers, computer room air conditioners (CRACs), pumps, etc., normalized by the computing equipment load. The Power Load Factor (PLF) is the total power dissipated by switch gear, uninterruptible power supplies (UPSs), power distribution units (PDUs), etc., normalized by the computing equipment Load. 
     Individual components may be measured in order to determine various information related to power efficiency metrics. In various embodiments described herein, equipment power is determined for various individual components, and this information provided to determine power usage related to that equipment. In various embodiments, a PDU is provided that senses and outputs the power used by various different components, including monitoring both the input power of the PDU and the power output to various components powered by the PDU. For example, to determine total computing equipment power (Power is (Volts×Amperes) or Watts) a PDU may measure Watts for each input cord to the PDU(s), or the input power at various subcomponents that provide power to one or more pieces of computing equipment. The sum of all the power output to pieces of equipment measures the total computing equipment power consumed by the computing equipment assuming all computing equipment assets are plugged into a PDU having the ability to measure power. 
     In other embodiments, an individual piece of computing equipment efficiency is determined according to MIPS/Watts. MIPS, as is well known, is Million Instructions Per Second, and is a measure of the speed of execution of a processor. Thus, a performance efficiency for a server, for example, may be measured and a cumulative efficiency calculated for all equipment in a data center. In embodiments that provide such metrics, each outlet measures power that is delivered from the outlet. The MIPS value may be read, for example, from the BIOS for the specific asset and provide a measure of performance efficiency. The sum of all the ‘per outlet Watts’ on a PDU may be used to measure the PDU&#39;s efficiency when compared to the input cord power to the PDU. In some embodiments, an individual piece of equipment may receive operating power from multiple power supplies. In such embodiments, the outlets that provide power to the piece of equipment are grouped with power from each outlet summed to provide the corresponding power measurement for the specific asset that is acquiring it power from multiple PDUs or multiple power supplies. Other embodiments provide the ability for an expense charge for the power consumed by each specific asset or assets associated with a particular cabinet, and each outlet, or cabinet power infeed, may record the amount of power used (Watts/hours) in the same manner as a utility meter. 
     Individual components may be measured in order to determine various types of information related to power efficiency metrics. In embodiments described herein, equipment power and related information is determined for various individual components, and this information provided to determine power usage related to that equipment. In some embodiments, a PDU is provided that senses and outputs the power used by various different components, including monitoring both the input power of the PDU and the power output to various components powered by the PDU. For example, to determine total computing equipment power (Power is (Volts×Amperes) or Watts) a PDU may measure Watts for each input cord to the PDU(s), or the input power at various subcomponents that provide power to one or more pieces of computing equipment. The sum of all the power output to pieces of equipment measures the total computing equipment power consumed by the computing equipment assuming all computing equipment assets are plugged into a PDU having the ability to measure power. In some embodiments, several metrics are calculated for each outlet in a PDU including voltage (true RMS Voltage), current (true RMS Current), active power (Watts), apparent power (VA), energy (Watt-hours), power factor (unitless), and crest factor (unitless). Each of these metrics may be used alone, or in combination with other of the metrics, to provide information related to components that are receiving power from the outputs of the PDU. 
     In other embodiments, the sum of all the ‘per outlet Watts’ on a PDU may be used to measure the PDU&#39;s efficiency when compared to the input cord power to the PDU. In some embodiments, an individual piece of equipment may receive operating power from multiple power supplies. In such embodiments, the outlets that provide power to the piece of equipment are grouped using an application external to the monitoring circuit, with metrics from each outlet in the group summed to provide the corresponding metrics for the specific asset that is acquiring it power from multiple PDUs/CDUs or multiple power supplies. 
     With reference now to  FIG. 2 , a block diagram of an exemplary system of an embodiment is now described. A power distribution unit (PDU)  20  supplies power to one or more associated computing assets. The PDU  20  may be a stand-alone device or incorporated with other components or modules to form a cabinet distribution unit (CDU) which includes, for example, fuse modules, environmental monitors, communications modules, other PDUs, etc. The PDU is useable in a computer network  24 , and may communicate over the computer network  24  with a network power manager application  28 . In cases where the PDU  20  is included in a CDU, communication with network power manager  28  is conducted through a communications module within the CDU. The network power manager  28  may reside in a workstation or other device that is used in the management of a data center or other enterprise management, and issues network commands over a network communications connection. 
     The PDU  20  of this embodiment includes a power supply  32 , a network interface card (NIC)  34  that has application firmware and hardware that interfaces to network the PDU  20  with other modules within a CDU, and in this embodiment includes a power manager agent application  36 . The PDU  20  includes a plurality of power outlets  40  arranged in a power distribution plugstrip within an intelligent power module (IPM)  44 . The NIC  34 , and power manager agent  36  are connected to the computer network  24 . The intelligent power module  44  controls the application of power from the input power to a corresponding power outlet among the power outlets  40 , and is in communication with the power manager agent application  36  to provide power and power cycling on-off for one or more of the corresponding power outlets, which may be accomplished through one or more relays  45  and associated relay driver  46 . The IPM  44  receives input power, and provides power to one or more outlets  40  through the relays  45 . The IPM  44  may also provide power state sensing and load-sensing with respect to the corresponding power outlet in response to one or more commands The IPM  44  in this embodiment includes a microprocessor  48  used to control the power applied to a corresponding power outlet. The microprocessor also is connected to a voltage sensing device  52  and a current sensing device  56  to sense the voltage and current at corresponding individual power outlet(s). The microprocessor  48  uses this information to determine the power supplied through an outlet, as will be described in more detail below. The microprocessor  48  also receives a power measurement from the input power supply  32  through an input voltage sensing device and an input current sensing device. In this embodiment, the IPM  44  also includes a power supply  58  used to provide DC operating power to components within the IPM  44 . 
     The network power manager  28  of  FIG. 2  communicates with the power manager agent  36  and IPM  44 . In this embodiment, the network power manager  28  may receive information from, and provide instructions to power manager agent  36  which communicates with IPM  44 . The network power manager  28  may also receive related power measurements from the IPM  44  (through power manager agent  36 ) and report power information related to the PDU  20 , and related to one or more individual outlets (and thus power information for individual assets powered by the outlet) of the PDU  20 . 
       FIG. 3  is an illustration of a CDU  65  that includes plugstrips  200 , along with a communications module  66  that provides communications functions, an environmental monitor  68 , and an input power cord  70  with associated plug  72 . The plugstrips  200  each include eight outlets  202 - 216  that supply power to assets that may be mounted into an equipment rack. Such equipment racks are well known, and often include several individual assets that are used in operation of a data center. The CDU  65 , as illustrated in  FIG. 3 , is configured to be vertically mounted in an equipment rack, commonly at the rear of the rack adjacent to the rear side of electronic equipment mounted in the rack. As is well known, numerous equipment racks may be included in a data center, and in various embodiments each asset in each equipment rack may be monitored for power usage through one or more associated plugstrips  200 . 
     With reference now to  FIG. 4 , a block diagram illustration of output power reporting components is now described for an exemplary embodiment. In this embodiment, the PDU includes a power outlet plugstrip  200 , also referred to as a power outlet module  200 , that includes eight power outlets,  202 - 216 . Each outlet  202 - 216  is connected to power lines L 1  and L 2  and to power source  32 . In this embodiment, the power line L 1  is connected to line power in the power source  32 , and the power line L 2  is connected to neutral in the power source  32 . However, in other embodiments the lines L 1  and L 2  may be interconnected to different phases of a polyphase power source. Each outlet  202 - 216  is also interconnected to a ground in the power source  32 , although this connection from the outlets  202 - 216  is not illustrated in  FIG. 4 . In this embodiment, each outlet  202 - 216  has an associated toroidal current sense transformer  202   a - 216   a  that senses current flowing through the line L 1  for each respective outlet  202 - 216 . The line L 1  interconnected to each outlet  202 - 216  is wired through the respective toroid  202   a - 216   a . The toroidal transformers  202   a - 216   a  each have a current reporting line  202   b - 216   b  that provides instantaneous current information related to the respective toroidal transformer  202   a - 216   a  to microcontroller  220 . Current information may be determined using other configurations, such as through the use of a shunt resistor, hall effect device, or other suitable current sensing device, as will be readily recognized by one of skill in the art. Such other configurations for determining the current provided to an outlet may be used in other embodiments. The microcontroller  220  receives this current information related to each respective outlet  202 - 216 . 
     The power outlet module  200  also includes one or more line voltage detectors, each including a voltage dropping resistor network  224 , and an opto-isolated operational amplifier  228  to provide an indication of instantaneous line voltage for the power source  32 . Similarly as described above, the line voltage may be determined through various other configurations as will be readily recognized by one of skill in the art. The line voltage detector, for example, may include a voltage sense transformer that provides isolation and allows voltage to be determined based on the voltage across the transformer and the turns ratio of the transformer. Other embodiments may not provide isolation, instead achieving isolation from high-voltages in other manners. The microcontroller uses the current information related to each of the respective outlets  202 - 216 , along with the line voltage to calculate the power metrics associated with each of the individual outlets  202 - 216 . This information may be communicated to other components through communications link  230  through, for example, a communications bus. 
     In one embodiment, the power outlet module  200  includes eight outlets ( 202 - 216 ) each of NEMA 5-20R type, contained in a housing. It will be understood that this embodiment, and other embodiments described herein as having NEMA 5-20R type outlets, are exemplary only and that any of various other types of outlets alternatively can be used. For example, the “outlets” can be other NEMA types (e.g., NEMA 5-15R, NEMA 6-20R, NEMA 6-30R or NEMA 6-50R) or any of various IEC types (e.g., IEC C13). It also will be understood that all the “outlets” in a particular power outlet module  200 , or other module-outlet described herein, need not be identical. It also will be understood that the “outlets” are not limited to three-prong receptacles; alternatively, one or more of the “outlets” can be configured for two or more than three prongs in the mating male connector. It also will be understood that the “outlets” are not limited to having female prong receptacles. In any “outlet,” one or more of the “prong receptacles” can be male instead of female connection elements, as conditions or needs indicate. In general, as used herein, female and male “prong receptacles” are termed “power-connection elements.” Furthermore, the principles described herein also are applicable to devices that may be hard-wired into an outlet module. While outlet module  200  of this embodiment includes eight outlets, it will be understood that this is but one example and that an outlet module may include a different number of outlets. 
     The housing for an outlet module may be any suitable housing for such a device, as is known to one of skill in the art, and may be assembled with other modules in a CDU. Such a housing generally includes a front portion and a rear portion, the front portion is substantially planar, and the rear portion is substantially planar and parallel to the front portion. The housing also includes longitudinally extending side portions and transverse end portions. The front portion, rear portion, side portions, and end portions are generally orthogonal to each other in a generally rectangular or box-type configuration. The housing can be made of any suitable, typically rigid, material, including, for example, a rigid polymeric (“plastic”) material. In at least certain embodiments, the front and rear portions are made from an electrically insulative material. The side portions and the end portions may be integrally formed, optionally along with the front portion or the rear portion. Furthermore, while the outlet module described in this embodiment includes a housing, other embodiments may include an outlet module that does not include a housing. For example, an outlet module may include a number of outlets coupled together with no exterior housing that may then be installed into another piece of equipment. 
     Each outlet  202 - 216  is interconnected to the power source  32  through any of a number of well known connection schemes, such as spade, lug, plug connectors, screw connectors, or other suitable type of connector. Furthermore, if desired, one or more of these electrical connectors can be located inside the housing or outside the housing, in embodiments where the power outlet module includes a housing. 
     The microcontroller  220 , in this embodiment, receives current information for each outlet  202 - 216 , along with voltage information and calculates various power-related metrics for each outlet, with this information reported through the communications link  230 . For example, the power per outlet is determined by multiplying the instantaneous voltage by the instantaneous current for a particular outlet, and integrating this product against time to give energy used (kilowatt hours, etc.) Examples of several metrics will be discussed in more detail below. 
     With reference now to  FIGS. 5-9 , schematic diagrams of an exemplary embodiment are now discussed. In this embodiment, various different components of an outlet module may be assembled onto separate circuit boards that are then assembled into a power outlet module of CDU. In such a manner, component boards may be assembled to include features that are ordered by a particular customer or user of a PDU in which the outlet module will be used. Furthermore, a user or customer may desire some, but not all, of the outlets in a PDU to have the capability of reporting power usage related to individual outlets, and thus different outlet modules, or subsets of outlets in a outlet module, may be assembled with the additional component boards to provide such capability. Similarly, in the embodiment of  FIGS. 5-9 , each outlet in the outlet module may be individually switched on or off through a sentry poer manager. However, other embodiments do not provide such switching capability, and the components described with respect to switching outlets would therefore not be included in such embodiments, replaced instead with simple pass-through components. 
     In this embodiment, an outlet module includes eight (8) individual outlets, that are organized into logical groups of four outlets each. Illustrated in  FIG. 5  is a schematic illustration of an outlet circuit  500  for such an embodiment. In this embodiment, eight outlets  502 - 516  are assembled to be included in an outlet module. In this embodiment, outlet  502  and  516  are IEC-C19 type connectors, and outlets  504 - 514  are each IEC-C13 type connectors, although it will be readily recognized that outlets may be any suitable outlet type as required for a particular application. The outlet circuit  500  includes a ground input  520  that is electrically connected to a ground connection in each respective outlet  502 - 516 . A neutral line may be electrically connected to each outlet  502 - 508  through a neutral input  524  that is provided for the four outlets  502 - 508 , with a neutral line electrically connected to each outlet  510 - 516  through a second neutral input  528 . Alternatively, if all eight outlets  502 - 516  are to be connected to a single power source, the neutral line for each set of four outlets may be connected through jumper connection  532 , with neutral inputs  536 ,  540  provided to electrically connect the neutral for each outlet  502 - 516 . As will be readily understood, a line voltage may be provided in place of a neutral connection in applications requiring higher voltages for the outlets  502 - 516 . 
     With continuing reference to  FIG. 5 , this embodiment provides a visual indicator at each outlet  502 - 516  that power is present at the outlet  502 - 516 . The visual indicator is provided through a LED  544  that is interconnected between line power and neutral for each outlet  502 - 516 . Line power for each outlet  502 - 516 , in this embodiment, is provided through line inputs  548 - 562 . Each line input  548 - 562  may be connected through a switch to line power from a power source, as will be described in more detail below. In such a manner, when a respective switch is configured to supply power to an outlet  502 - 516 , the LED  544  associated with the outlet  502 - 516  will illuminate, thus providing a true visual indicator that power is being provided to a particular outlet  502 - 516 . The LED  544 , in this embodiment, is electrically connected between the line input and neutral through current limiting resistors  570  and diode  566 . In other embodiments, such a visual indicator may not be desired, and in such embodiments the components related to the visual indicator may be omitted. As mentioned, line power is provided through separate line inputs  548 - 562  for each respective outlet  502 - 516 . In some embodiments, the line inputs  548 - 562  are electrically connected to switches to provide switched electrical outputs  502 - 516 , and in other embodiments some or all of the line inputs  548 - 562  may be connected in an unswitched configuration to a line power input to provide unswitched outputs. 
     As mentioned, in some embodiments switched outputs are provided. With reference now to  FIG. 6 , provided in this embodiment is a relay circuit  600 . The relay circuit  600  may be provided on a separate printed circuit board that is configured to couple with the outlet circuit  500 . In such a manner, if switched outlets are required for an outlet module, the relay circuit may be assembled with the outlet module to provide such functionality. When switched outputs are not provided, this circuit board may be replaced with a simple pass-through circuit board having the same connections to other circuit boards, simplifying assembly and manufacturing of such power outlet modules. The relay circuit  600  includes relays  602 - 616  that provide line power to each outlet  502 - 516 , respectively. The output of each relay  602 - 616  is provided to line power outputs  648 - 662  that, when coupled to outlet circuit  500 , are connected to line inputs  548 - 562 , respectively. Line power is provided to the relay circuit  600  through jumpered line power input  670  when all eight outlets  502 - 516  receive power form one line power input, and through power inputs  672  and  674  (with jumper  670  omitted) when a line power input is provided for each set of four outlets  502 - 508 , and  510 - 516 . 
     Each relay  602 - 616  is connected to a relay driver circuit  678 - 692 , respectively, that provide signals to switch the relays  602 - 616 . The relay driver circuits  678 - 692  are electrically connected through a connection  696  to a microcontroller. In this embodiment, relay driver circuits  678 - 692  each include a switching transistor  698  and a holding transistor  699 . When the relay control circuit provides voltage to switch a particular relay driver circuit  678 - 692 , the voltage is applied directly to the holding transistor  699  and the switching transistor  698  through a capacitor  700  and a resistor  702 . In this manner, upon the application of voltage to the relay circuits, both the switching transistor  698  and the holding transistor  699  receive voltage and act to switch the respective relay  602 - 616  and connect line power to the respective outlet receptacle. After a short time period, the capacitor  700  charges and reduces current flow through resistor  702  such that the voltage at the switching transistor  698  drops and the switching transistor  698  switches off. The holding transistor  699  continues to provide adequate voltage to hold the respective relay  602 - 616  closed with reduced current through current limiting resistors  703 . 
     In such a manner, the power required to hold the relays  602 - 616  is reduced as compared to the power required to initially switch the relays  620 - 616  from open to closed. In one embodiment, the holding transistor requires about 75% of the power to maintain the relays  602 - 616  closed than would be present if a single transistor were used to both switch and hold. In embodiments where numerous switched outlets are present in a facility, such power savings can be significant in operating power reduction for the associated CDUs, which in turn reduces heating, allows for increased component density on a circuit board or within a housing, and also increases the lifetime of components. Other embodiments, however, may include different switching components as will be readily apparent to one of skill in the art. 
     With reference now to  FIG. 7 , current sensing is described for this embodiment. A current sensing circuit  710 , in this embodiment, is included as a separate printed circuit board that can be assembled into a power outlet module when it is desired to have the capability to provide current information related to each individual outlet in an outlet module. Such a circuit board may be used in conjunction with other circuit boards, such as the relay circuit  600  of  FIG. 6 . Such a configuration is illustrated in  FIG. 12 , in which the circuitry of  FIG. 5  is contained on the middle printed circuit board  754 , the circuitry of  FIGS. 7-9  are contained on the middle circuit board  754 , and the circuitry of  FIG. 6  is contained on the upper circuit board  758 . The electrical connections of each of the circuit boards may be designed such that the boards may be assembled with related inputs/outputs and connections that are aligned so as to provide for efficient modular assembly of power outlet modules that incorporate some or all of the features described herein through the addition of one or more related printed circuit boards. 
     As illustrated in  FIG. 7 , current transformers (CTs)  712 - 726  are provided that sense current flowing in an associated conductor that is routed through the individual CT  712 - 726 . The current transformers  712 - 726  in this embodiment are zero-phase toroidal inductors that each have two output lines, the output proportional to the magnitude of the current that is flowing through the conductor associated with the CT. In this embodiment, the line power conductor for each outlet  502 - 516  is routed through a corresponding CT  712 - 726 . The respective CT  712 - 726  outputs a signal that corresponds to the magnitude of the current which, in this embodiment, is output on two output leads across a burden resistor  730 . This configuration provides the ability to sense output currents up to 16 amperes with a maximum crest factor of 2.5, although it will be readily apparent to one of skill in the art that other configurations are possible. 
     In the embodiment of  FIG. 7 , each CT  712 - 726  output lead includes a related passive two-pole anti-aliasing filter  732 ,  734  to provide current sense outputs  712   a ,  712   b  through  726   a ,  726   b  for each outlet. The current sense outputs  712   a ,  712   b - 726   a ,  726   b  are provided as differential input to a microcontroller differential analog-to-digital input for use in determining the power metrics related to a particular outlet. Also provided to the power sensor is information related to the line voltage that is present on each outlet so as to provide voltage and current information for use in determining power metrics. In this embodiment, as will be described in more detail below, the power sensor is a microcontroller that includes an analog-to-digital converter with inputs for the current sense outputs  712   a ,  712   b  through  726   a ,  726   b , as well as voltage sense inputs for line voltage. 
     Line voltage measurements are provided, in this embodiment, through a voltage sensor circuit  800  that is illustrated in  FIG. 8 . The voltage sensor circuit  800  includes a voltage dropping resistor circuit  804  that is connected to line power source at a first end  808 , and connected to the neutral input at a second end  812 . The voltage dropping resistor network  804  is tapped between resistors and at the neutral input with the taps provided to positive and negative voltage inputs to an opto-isolated amplifying circuit  816 . Similarly as described above, other voltage sensing circuits may be used, such as a voltage sense transformer may be used instead of a voltage dropping resistor network, for example. Also, in some embodiments voltage sensing may be provided that is not opto-isolated with any required isolation provided by other well known methods. The output of the opto-isolated amplifying circuit  816  is provided as a voltage sense signal  820  through a passive two-pole anti-aliasing filter. 
     In the embodiment of  FIG. 8 , an opto-coupler  824  is connected to the line input and provides a frequency sense signal  826  to indicate that AC line voltage is present at the outlet module and also provides an approximately 50% duty cycle output that is based on the line frequency of the input power. Thus, for each AC cycle of the input power, the frequency sense signal  826  will have a logical high signal for approximately one half of the AC cycle. The leading or trailing edge provided by the frequency sense signal  826  provides an accurate measurement of the frequency of the input power frequency that may be used by a processing circuit to synchronize power metrics to an AC cycle. 
     In embodiments where all of the outlets of an outlet module are powered by a single power source, a single voltage sensor circuit  800  is used, and in embodiments where different outlets in the outlet module are supplied power from different power sources, a second voltage sensor circuit is provided for the second power input to the outlet module. As discussed above, this embodiment may be implemented using printed circuit boards that provide circuitry for various features described. In this embodiment, the voltage sensor circuit(s) are provided on the same printed circuit board as the current sensor circuit  710 , although it will be readily recognized that other configurations may be implemented. 
     Referring now to  FIG. 9 , a power sensor and control circuit  900  is described for an embodiment. The power sensor and control circuit  900 , in this embodiment, is included on the same printed circuit board as the current and voltage sensor circuits  700 ,  800 , although other implementations will be readily recognized. The power sensor and control circuit  900  includes a microcontroller  904  that receives all of the current sense signals  712   a ,  712   b  through  726   a ,  726   b , and receives voltage sense signal(s)  820 . These signals are received and processed to determine the power metrics related to each outlet  502 - 516  in the outlet module. The microcontroller  904  is interconnected to an addressable latch  908  that provides control signals to the relay drivers  678 - 692  and relays  602 - 616 , if present. The microcontroller  904  also includes communications connections  912  that may be coupled to a communications bus to receive and transmit data from/to the bus. In this embodiment, the microcontroller  904  has 16 current input channels, two per outlet, which are electrically connected to the current sense outputs  712   a ,  712   b  through  726   a ,  726   b , and two voltage input channels which are electrically connected to voltage sense output(s)  820 . The microcontroller includes ADC inputs that digitize the current and voltage sense signals. Relative to the current sense signals, the ADC includes a differential ADC input based on the two inputs from the current sensor associated with each outlet. 
     In this embodiment, the microcontroller  904  filters the current and voltage sense signals to reduce high-frequency noise that may be present. The digitized current sense signals are scaled for 16 Amps with a 2.5 crest factor, in this embodiment. The voltage sense signals(s) are received on voltage input channels. In embodiments having different power sources for some outlets, one voltage input channel per outlet group is provided. The voltage input channels are provided to a single-ended ADC input and a digitized output scaled for +/−390 volt peaks. The frequency sense signals for each power source are also provided to the microcontroller. The frequency sense signal(s), in some embodiments, is (are) used for frequency determination and timing of cycle sampling to provide accurate correlation of inputs to a particular AC cycle. The timing, in an embodiment, is auto-adjusted every second to compensate for inaccuracies, such as temperature drift, in the internal clock of microcontroller  904 . 
     Use of the frequency sense signal  826  provides for accurate timing in the microcontroller  904  without the use of an external oscillator as an accurate time base. The ability to measure the frequency sense signal  826  provides enhanced accuracy for timing used in calculating power-related metrics for each outlet. In this exemplary embodiment, two signals are digitized by an ADC within the microcontroller, the voltage and current signals. Each cycle of power, as synchronized with the frequency sense signal  826 , provides for measurements that are accurately aligned with an AC cycle and provides enhanced accuracy in the power-related measurements. It is well known that internal clocks in microcontrollers such as microcontroller  904  have some variability, such as plus or minus two percent. Such internal clocks are typically subject to frequency shift with changing temperature and variability between different microcontrollers. In this embodiment, the frequency sense input allows cycle timing of any one AC cycle to be measured to within plus or minus 240 nanoseconds of the actual AC cycle. The voltage and current sense inputs on the microcontroller  904  are sampled nearly simultaneously 120 times per any AC cycle. The number of samples per cycle, 120 in this example, provides sampling of frequency content up to the 14th harmonic of a 50 or 60 hertz power input, allowing for measurement of real energy at harmonics present in a non-perfect sinusoid. The ADC, in an embodiment, within the microcontroller is a 10-bit ADC hardware, with four times over-sampling to provide an effective 11-bit ADC. 
     The computation of several power metrics will now be described, for an exemplary embodiment. In this embodiment, discrete samples are taken for one current and voltage channel for an AC cycle, which produces a digital measurement for each sample. After the samples are taken for a cycle, calculations are performed by the microcontroller, these calculations performed over about the next one-and-a-half AC cycles in this embodiment. After the calculations are performed, the next channel is sampled beginning at the start of the next AC cycle. Thus, in this embodiment, there are three cycles dedicated to the first channel, the next three cycles dedicated to the second channel, and so on. Accordingly, in this embodiment with eight outputs monitored, each channel is sampled once every 24 AC cycles. 
     Also, voltage and current inputs are calibrated and provided to the microcontroller  904  in some embodiments. The current inputs, in an embodiment, are scaled to 16 amps at 2.5 crest factor and with the voltage input(s) scaled for 390 volts. Variances in the resistors and toroids, in an embodiment, is accounted for through calibration of the input channels. In one embodiment, the voltage and the current are calibrated based on active power and apparent power for each channel, although calibration based on other metrics may be used, such as calibrating the voltage and current individually. In embodiments that calibrate current and voltage individually, any errors that are in opposite directions will tend to cancel, and any errors in the same direction will be multiplied, when doing a power calculation. In embodiments that calibrate based on active and apparent power, the multiplied error may be reduced. The microcontroller  904 , in this embodiment, also provides for calibrations to account for system phase error and provide near-zero to near-full-span voltage and near-zero to near-full-span current digitization. 
     With reference now to  FIG. 10 , a block diagram illustration of a microcontroller  904  is provided for an exemplary embodiment. The microcontroller  904 , as mentioned above, includes an analog-to-digital converter  906  that receives an input from the current sensors and the voltage sensors. Samples from the ADC  906  are provided to processing logic  908 . A memory  910  is interconnected to the processing logic  908  and may be used to store information related to power metrics and sampled current and voltage information, as well as any programming used by the processing logic. An internal clock  912  provides an internal time base, and as discussed above the processing logic  908  also receives a frequency sense signal that allows accurate synchronization with an AC cycle. The microcontroller  904  also includes a relay control  914  and a communications interface  916 . The communications interface may be used to receive and transmit information from/to a communications bus, such as power metrics computed by the processing logic, control commands to actuate different relays through the relay control  914 , etc. 
     With reference now to  FIG. 11 , the operational steps of a microcontroller for determining power metric related information are described for an exemplary embodiment. In this embodiment, the ADC  906  is a 10 bit ADC, with both single-ended channels for voltage sense inputs, and differential channels for the current sense inputs. As mentioned above, 120 samples of voltage and current are taken for each cycle in an embodiment. Each of those samples, 120 over the AC cycle, are taken nearly simultaneously for both the current and voltage. In an embodiment, the samples are taken in successive samples by the ADC  906  to provide samples are on the order of microseconds apart for a relatively small error effect on overall calculations. 
     Each voltage and current sample is stored in memory  910  as an integer value. For each set of current and voltage samples, the processing logic calculates the true RMS voltage and current in several steps. First, each data point in the 120 samples is summed together and then divided by 120 to get the mean of the samples. Then, for each sample, the processing logic calculates the difference of that sample from the mean (floating point values). Each difference from the mean is squared, and the sum of the square of every point&#39;s difference from the mean is calculated. This total sum is divided by 120. The raw RMS value is then determined as the square root of the resulting quotient. This number is scaled by the calibrated scale factor to produce a calibrated value, referred to as a true RMS value, which is stored in memory  910  for both the set of the current data points and the set of voltage data points. The result is RMS current and the RMS voltage values. In this manner, an AC RMS value is generated that removes any DC offset present from the sensing circuitry or the signal itself. 
     In one embodiment, the samples of voltage and current in a waveform are compared against a model waveform or a historical waveform for that particular channel, and any significant deviations from the comparison may be flagged as anomalous indicating that there has been a change related to the associated component. Such a change may indicate the component may not be operating properly, may be about to fail, or may have had a failure. For example, waveforms of the current drawn by a device and the voltage drawn by the device, when compared to historical or reference waveforms, may indicate a fault or other condition that should be investigated. For example, a switched-mode power supply located within a server that receives power from a PDU may be drawing power in a manner that indicates an imminent failure. Embodiments described herein provide the ability to assess the health of such power supplies an installed base of power supplies in data center equipment racks without requiring any modification of the power supplies. 
     In some embodiments, currently sampled waveform information is only maintained in memory long enough to be utilized to generate and report the noted power metrics. Other waveforms, however, may be maintained in memory for comparison, such as in the form of or representative of one or more sample or reference waveforms or portions of one or more waveforms. In addition, the waveform information might be maintained in memory longer or otherwise stored for later use in, e.g., providing a basis for comparison. For example, when a system is initially set up and tested, the waveform may be stored and used for later comparison. 
     Referring again to  FIG. 11 , power for each cycle is determined by first, for each of the 120 data points for current and voltage, calculating products of each respective sample. These 120 products make up the waveform of the wattage that may be compared to model or historical waveforms to identify any potential problems related to the component that is receiving power from the associated outlet. The sum of the products of each current and voltage data point is then divided by 120 to get the average power, referred to as active power. It is noted that, in this embodiment, zero-phase toroidal current transformer are used and the voltage and the current samples are digitized approximately simultaneously, and thus the phase angle created by loads is inherent in this measurement. This phase angle may be determined as the inverse cosine of the power factor, as will be described in more detail below. 
     Also calculated is apparent power, which is the product of the RMS current and the RMS voltage calculated earlier, having units of volt-amps or VA. Power factor, the ratio of the active power to the apparent power, is calculated, which directly relates to the phase angle difference between the current and voltage. Power factor is calculated by taking the active power calculated from all the data points divided by the apparent power, which was the product of the RMS current voltage. The next item measured in this embodiment is current crest factor. The current crest factor is the ratio of the peak of the current waveform to the RMS of the current waveform. 
     Finally, energy is calculated. As mentioned above, embodiments are provided in which the microcontroller does not receive a time base from an external oscillator. The timing for such embodiments is based on cycles of the incoming AC waveform. As is well known, frequency of incoming AC power is generally 50 Hz or 60 Hz, depending upon location. Furthermore, most, if not all, industrialized nations have electrical generation and distribution systems that provide a relatively stable frequency of incoming AC power. The stability of incoming AC frequency may be used to provide a relatively accurate timing mechanism for starting and stopping ADC conversions. As described above, one embodiment samples eight channels over the course of 24 AC cycles. The relative accuracy of the incoming AC signal as a time base provides knowledge that there is an accurate measuring every 24th cycle for each channel with very little drift. 
     In an embodiment, the on-sense signal is sampled to determine if the input power is 50 Hz or 60 Hz. At 60 hertz there are 216,000 cycles in an hour, and at 50 hertz there are 180,000 cycles in an hour. Based in this information, combined with the measurement of one current channel every 24 cycles, energy may be calculated by multiplying the active power times  24 , representing the all 24 cycles between measurements on a channel, and dividing by either 180,000 (at 50 hertz) or 216,000 (at 60 hertz). This provides a representation for power consumed by the channel during the 24 cycles. This energy computation is added to an energy accumulator associated with each channel. Each time the power for a channel is computed, the wattage use for the represented 24 cycles is added to the accumulator. In one embodiment, to reduce rounding errors, when the accumulator (a floating point data type in memory) exceeds one, the accumulator is decremented and a double word integer associated with the channel is incremented to provide a number representing whole watt hours that have been measured for the channel. All of the values stored in memory may be reported through the communication interface to power managers or other applications that may then use this information to provide a number of different power-related metrics for components that receive operating power from the PDU. 
     As discussed above, relatively accurate timing is achieved in embodiments with a relatively high variability internal microcontroller clock though adjustments that compensate for inaccuracies in the internal clock. The compensation is achieved, in an embodiment, through providing the frequency sense input into an external interrupt pin on the microcontroller. The frequency sense signal, as discussed above with respect to the embodiment of  FIG. 8 , may be generated from a photo-optic diode  824 . As the voltage rises on the input power, the LED of the photo-optic diode turns on, and the LED will turn off slightly above the zero crossing of the input waveform, regardless of the duty cycle. As a result, every second edge of the frequency-sense signal is the frequency of the line input. The microcontroller, in this embodiment, is programmed to identify a positive edge of the frequency sense signal. 
     Once a positive edge is identified, then the first negative edge is identified. The interrupt within interrupt service routines for the external interrupt pin in the microcontroller is set to high priority to have relatively few, if any, interruptions from any other software interrupt service routines. When the first negative edge is detected, the microcontroller starts running a counter that counts every 12 clocks of the internal clock  912 . In one embodiment, the internal clock  912  is nominally a 25 megahertz internal clock plus or minus 2%. The timer runs until the next negative edge is detected. Thus, regardless of the timing of the internal clock  912 , a number of system clocks is determined that represents the span of time, from the microcontroller&#39;s view, of a single AC cycle. This number is converted into entire system clocks for an AC cycle by multiplying by 12, and then divided that by the number of samples collected within a single AC cycle (120 in this embodiment). Thus, a number of clocks is calculated that represents the time span for each sample of an AC cycle. This time is adjusted for expected interrupt latencies in the microprocessor, due to known entry and exit times in the interrupt service routines, etc., to generate a number and system clocks that represents the AC cycle. This value becomes a reload value for the timer that starts off each ADC conversion. 
     Thus, the timer becomes a time base for the digitizer of the ADC, and continues to be the time base for cycles when digitizing is not performed. Errors in the time base may accumulate over time. In one embodiment, errors are reduced by periodically re-measuring the number of system clocks in an AC cycle, such as once every five seconds. Such re-measuring provides adjustment to account for the actual speed of the internal clock, and also synchronizes the timer to a zero crossing of the voltage waveform. Such timing and synchronization of timers to an AC cycle provides relatively accurate power metrics. For example, if an external crystal time base were used, which is also susceptible to temperature change and variability of the incoming AC signal, errors can be introduced in between the timing of AC cycles and also synchronization to AC cycles. In the embodiments described here, the timer is re-synced to provide greater confidence that the samples used for RMS calculations are within the actual AC cycle. If RMS calculations are based on samples that begin after the cycle begins, or that end after the end of the cycle error can be introduced to report either less or more energy than is being integrated. By re-syncing, sampling is more likely to be within a cycle and not outside the cycle, and thereby improves accuracy. 
     As mentioned above, to determine energy, an accurate measure of time is needed to provide, for example, a watt-hours number. The above description relies on the assumption of 50 or 60 hertz input signal being accurate. In some embodiments, the time as measured in the microcontroller is compared to time provided by a network controller to verify or adjust energy calculations. In one embodiment, the number of cycles counted in a timeframe of an hour is provided to a network card and compared to an actual real time clock view of an hour. In the event of any significant deviation, the network card may add a simple correction scale in for that. For example, if the microcontroller counts up number of clock cycles in an hour and reports to the network card, which measures 59 minutes, a simple adjustment may be made to the energy value. 
     In another embodiment, the timing of the AC cycles provides an indication related to when the incoming power waveform is at a zero-crossing. In this embodiment, the switching on and off of the relays (such as in  FIG. 6 ) is performed around the zero-crossings on the voltage AC waveform, or at least at a point less than the peak value of the waveform. Such switching acts to reduce noise from the relays when switching, and may also extend the life of the relays. Reduced noise results, in part, because switching at a zero-crossing results in relatively low, or no, voltage potential at the physical points within the relay, thereby reducing noise when the relay is switched. Furthermore, the point life of such relays may be extended due to lower stress than would be present when switching occurs with a relatively high voltage present at the relay. A further advantage of switching at or near zero-crossings is a reduction in the in-rush currents experienced by a piece of equipment. For example, if the points on a relay are closed as the top of the sine wave, the in-rush current would be significantly higher than present if switching is performed at or near a zero-crossing. Such zero-crossing switching allows the in-rush current build as the sine wave builds from the zero crossing. In this manner, the entire chain of current path is also less stressed. 
     While described above with respect to a CDU, it will be understood that the power measurement circuitry and portions thereof have many applications beyond the exemplary embodiments described above. For example, a low-cost power metering circuit such as described may be incorporated into other equipment to provide information related to power parameters for the particular equipment. A server may, for example, include a power circuit as described to provide power-related information that may be used to assist in managing efficiency of the server by, for example, identifying that a server is not operating efficiently and that the load being serviced by the server may be a target to be moved to a different server. Similarly, it has been desired to have a switched-mode power supply that provides power-related information, but there is a strong desire to maintain as low a cost for these power supplies as possible. A single-chip solution without an external oscillator time base as described herein may provide a low-cost solution for incorporation into such power supplies. Further, such power metering may be incorporated into residential, commercial and multiple-unit power meters to provide power-related information for billing purposes. 
     With reference again to  FIG. 8 , as mentioned above an outlet module may include power outputs that are connected to separate line inputs. In such cases, separate voltage sensor circuits  800  are used for each set of outlets. Separate voltage sense circuits for each branch of outlets may be desired for a number of reasons, such as separate branches protected by different fuses or circuit breakers, and one branch may have a fuse blown or the circuit breaker tripped and it could be off while power is still being supplied to the other outlets. Also, those two branches may be operated at different voltages, like a three-phase 208 volt wye system. Two volt sense circuits  800  allow the two different voltage values in that split branch configuration to be measured and used in power metric calculations. Also, the on-sense may be used to detect an absence of voltage that may result from many different sources, one being a fuse or circuit breaker that has faulted. In cases where the power supply provides an on-sense, this can be used to determine whether the line has failed or a fuse has blown. 
     As discussed above, the microcontroller  904  is interconnected to a communications bus (such as an I2C bus or SMBus). The microcontroller  904  reports over the bus, for each outlet/channel: (a) Voltage RMS (Vrms)—the pseudo-running-average of the eight most-recent Vrms values reported to a tenth volt; (b) Current RMS (Irms)—the pseudo-running-average of the eight most-recent Irms values reported to a hundredth Ampere; (c) Apparent Power (VA)—the pseudo-running-average of the eight most-recent VA values reported to in volt-amps; (d) Active Power (W)—the pseudo-running-average of the eight most-recent active power values reported in watts; (e) Power Factor (pF)—the pseudo-running-average of the eight most-recent pF values reported to a tenth; and (f) crest factor. This data may be received by an external system that collects the outlet information for which the data is provided, and used to determine metrics or provide information such as described above. 
     With reference now to  FIG. 13  is an illustration of a circuit board configuration of an embodiment. In this embodiment, the components described above with respect to the three circuit boards as illustrated in  FIGS. 4-8  are provided on a single circuit board. In this embodiment, power outlets  950  are provided that have a neutral line and a ground that are provided by a bus bar (not shown). The line power is provided to outlets  950  through a line connection  954  that is routed through a relay  958  and an associated current transformer  962 . The relays  958  and current transformers  962  are interconnected to control and monitoring circuitry such as illustrated in  FIGS. 4-8 . In this embodiment, the printed circuit board  966  is mounted at a 90 degree angle relative to the plane of the outlets  950 . In this manner, the additional surface area required by the circuit board  966  is provided in a plane that is generally perpendicular to the plane of the outlets  950 , rather than in a parallel plane as illustrated in the embodiment of  FIG. 12 . By configuring the circuit board  966  perpendicular to the plane of the outlets  950 , this additional surface area can be accommodated simply be making the PDU housing somewhat deeper, with the width of the housing remaining substantially the same as the embodiment of  FIG. 12 . Using a single printed circuit board  966  allows a reduced manufacturing cost and provides efficiencies in manufacturing due to reduced assembly steps relative to embodiments with more than one printed circuit board. 
     Those of skill will appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, firmware, or combinations thereof. To clearly illustrate this interchangeability, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware, software, or firmware depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention. 
     For a hardware implementation, the processing units may be implemented within one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, micro-controllers, microprocessors, electronic devices, other electronic units designed to perform the functions described herein, or a combination thereof. For a firmware and/or software implementation, the methodologies may be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein. 
     A power management system embodying aspects of the invention is illustrated in  FIG. 14 . A first equipment cabinet  2401  houses components  2403 ,  2405 ,  2407 ,  2409 ,  2411  and  2413 . Also in the cabinet are a first CDU  2415  and a second CDU  2417 . The CDUs are shown outside of, and larger than, the cabinet for convenience. Each CDU is similar to the CDU depicted in  FIG. 3 . The component  2403  is shown both installed within, and outside of, the cabinet. The component  2403  draws power from both CDUs as indicated by a cord  2419  connecting the component  2403  to an outlet in the first CDU  2415  and a cord  2421  connecting the component  2403  to an outlet in the second CDU  2417 . Others of the components may be connected to one or both of the CDUs as desired. 
     Similarly, a second equipment cabinet  2423  houses various components and one or more CDUs that provide power to these components. The system may include other equipment cabinets having more or fewer components or CDUs than depicted in the drawing. 
     The CDUs in the various cabinets communicate, for example through an Ethernet pipeline  2425  or through the Internet or some other suitable medium, with a server  2427 . The server  2427  includes a database  2429  which may be stored in a memory, or on a magnetic disk or other medium. The database  2429  may be located in one place or distributed as desired. In some embodiments the server  2429  communicates with another system such as a Building Management System  2431 . 
     As discussed previously, various electrical parameters respecting one or more of the outlets may be measured and used in managing power throughout the system. Current flow through each outlet, voltage present at the outlets, power factor, phase, power line frequency, and the like may all be measured and the measurements communicated to the server for presentation to a user or for preparing reports, generating messages, providing trends, and the like. 
     While embodiments discussed above describe exemplary implementations of components within an equipment rack or CDU, one or more of the principles, aspects, or features described above may be used in other applications. For example, generation of power metrics as described above, as well as internal clocking based on an incoming AC signal, may be incorporated in or with a power supply, such as a switched-mode power supply, to provide metrics related to the power supply or to otherwise use them or the underlying operation or information monitoring in association with the power supply or associated components or systems. For example, in this fashion such a power supply may monitor itself, take corrective or other action based on (in whole or in part) internal monitoring, and report out one or more power metrics. Such metrics may be used, for example, to anticipate power supply failure, measure power supply efficiency, and adjust the power supply to be more efficient for a given load. 
     With reference now to  FIG. 15 , an embodiment illustrating power monitoring incorporated with a switch mode power supply is illustrated. In this embodiment, a switch mode power supply  3000  receives incoming AC power from an AC line source  3010 . This embodiment includes voltage and current monitoring for both the high side, that is the high voltage AC input power, and the low side that is the relatively low voltage DC output from the switch mode power supply  3000 . The switch mode power supply  3000  is used to provide power to a load  3020 , which may be any device or asset that receives power from the switch mode power supply  3000 . The load  3020  is modeled as a resistive load in this illustration, although it will be readily recognized that such loads are not necessarily purely resistive loads, and in many cases if the load is operating at less than optimal conditions, the load  3020  may be a reactive load or have a larger reactive component relative to a load operating at optimal conditions. 
     A microcontroller  3030  receives an input from a toroidal current transformer  3040  associated with the high side AC power source. The output of the current transformer  3040  indicates the instantaneous magnitude of the current that is flowing through the input AC line, and may be configured such at current transformers described above. The output of a voltage sense circuit  3050  is also received at the microcontroller  3030 . The voltage sense circuit  3050  may include an isolating amplifier that amplifies voltage from a voltage divider network  3060 , and may also include a frequency sense output such as described above. 
     The microcontroller  3030  of this embodiment also receives input related to low side current and voltage. Current from the low side may be input through a shunt resistor  3060  having a known resistance, the voltage across this shunt resistor  3060  used to calculate the current provided to the load  3020 . Low side voltage is provided from a voltage divider network  3070 . It is noted that the low side current and voltage sense signals are not isolated signals, as these signals in this embodiment have relatively low voltage levels that do not require isolation. It will be understood that necessary isolation may be achieved according to any suitable isolation. The microcontroller  3030  operates to collect information related to the voltage and current inputs and may process and output information in manners such as described above to provide power metrics related to the switch mode power supply  3000 . The output from the microcontroller  3030  may be through a communications buss  3080  as illustrated in  FIG. 14 , although other communication may be utilized such as wireless communications. The microcontroller  3030  of this embodiment also provides a control output  3090  that may be used to control one or more other components associated with the switch mode power supply  3000 . 
     For example, typical power supplies are most efficient, naturally and when in good operating order, at a load of 80-90% of standard capacity. If a power supply load is only 60% of capacity, and the load appears static, the power supply could “adjust itself” internally, based on the load, to be more efficient. Embodiments such as described above can provide the metrics or underlying measurements (e.g., waveform comparisons) to trigger the adjustment. The power supply can also include a remote reporting capability to report out information. 
     With reference now to  FIG. 16 , a PDU  1600  of another embodiment is described, in which power related metrics are measured at an input power sensor  1604  at the input to the PDU  1600 . In the event that a PDU includes more than one input, power may be measured at each input and provided separately, or aggregated, to provide power related metrics for the inputs. Such input power measurement is referred to as Per Inlet Power Sensing, or PIPS. In this embodiment, users may view and understand power information, including total power consumed through a given PDU, by monitoring a given PDU&#39;s A.C. power in-feed connections. When referring to “in-feed,” or “power input”, reference is made to a single power cord containing one or more AC (hot) conductors, and potentially a neutral conductor or an Earth Ground conductor. The PDU  1600  includes various other components and may be interconnected to other network components as described above with respect to  FIG. 2 . The current and voltage sensors ( 52 ,  56 ) for the outputs of a PDU, as described in  FIG. 2 , may also be included in some embodiments, thus providing a PDU having both PIPS and POPS capability. Such a PDU may or may not include relays to individually control individual outlets in combination with PIPS and/or POPS. 
       FIG. 17  is a block diagram illustration of an input power sensor  1604  of an embodiment. In this embodiment, a current sensor  1608  is connected to the input power line and provides an instantaneous output that is proportional to the current that is passing through the input power line. A voltage sensor  1612  is also connected to the input power line and provides an instantaneous output that is proportional to the voltage that is present at the input power line. In one embodiment, the current sensor  1608  includes a current transformer (CT) that senses current flowing in an associated conductor that is routed through the CT. The current transformer, in an embodiment, is a zero-phase toroidal inductor that has two output lines. The output is proportional to the magnitude of the current flowing through the conductor associated with the CT. In this embodiment, the CT outputs a signal that corresponds to the magnitude of the current and is output on two output leads across a burden resistor. This configuration provides the ability to sense output currents up to 63 amperes with a maximum crest factor of 3.0, although it will be readily apparent to one of skill in the art that other configurations are possible. In one embodiment the CT output lead includes a related passive two-pole anti-aliasing filter to provide current sense outputs for the input power line. The current sense outputs are provided as differential input to an analog-to-digital converter  1616  input for use in determining the power metrics related to the power input. 
     Also provided to the ADC  1616  is information related to the line voltage from voltage sensor  1612 . In one embodiment, the line voltage sensor  1612  is a potential transformer (PT) that senses the voltage on the input power line. The PT, in an embodiment, has two output lines, the output proportional to the magnitude of the voltage present between two phases of a polyphase input, or between hot and neutral or ground inputs in a single phase input. In this embodiment, the PT outputs a signal that corresponds to the magnitude of the voltage and is output on two output leads across a burden resistor. This configuration provides the ability to sense output voltages between 85V and 265V for single phase configurations, and 187V to 415V for polyphase configurations, although it will be readily apparent to one of skill in the art that other configurations are possible. In one embodiment the PT output lead includes a related passive two-pole anti-aliasing filter to provide voltage sense outputs for the input power line. The voltage sense outputs are provided as differential inputs to an input of an analog-to-digital converter  1616  for use in determining the power metrics related to the power input. As will be readily apparent to one of skill in the art, other voltage sensing circuits may be used, such as a voltage dropping resistor network, for example. 
     In the embodiment of  FIG. 17 , the input power sensor  1604  includes the analog to digital converter  1616 , which is a 10 bit ADC with differential channels for the current sense and voltage sense inputs. The voltage and current input signals of this embodiment are differentially filtered through passive RC filters that are two stage (−12 dB/octave; −40 dB/decade) anti-aliasing filters with a cut-off frequency of ˜159 KHz. The approximate phase shift (Φ) of these filters is 0.0368 at 50 Hz, and 0.0438 at 60 Hz. Samples from the ADC  1616  are provided to processing logic  1620 . A memory  1624  is interconnected to the processing logic  1620  and may be used to store information related to power metrics and sampled current and voltage information, as well as any programming used by the processing logic. An internal clock  1628  provides an internal time base. In one embodiment, the processing logic  1620  also receives a frequency sense signal that allows accurate synchronization with an AC cycle, in a manner similar as described above with respect to  FIG. 10 . 
     The power sensor  1604  also includes a communications interface  1632 . The communications interface may be used to receive and transmit information from/to a communications bus, such as power metrics computed by the processing logic. In one embodiment, the communications bus is an I2C bus, and electrical parametrics from the power sensor  1604  are communicated to power manager agent  36  via the I2C bus. In the embodiment illustrated in  FIG. 17 , the power sensor  1604  may include a temperature sensor  1636  that is used to compensate for temperature-related variances in the outputs of the current and voltage sensors  1608 ,  1612 . In one embodiment, the ADC  1616 , processing logic  1620 , memory  1624 , clock  1628 , and communications interface  1632  are all implemented in a microcontroller. In an embodiment, such a microcontroller is a Silicon Labs 8051-based F311 microcontroller chip (IC). The power sensor  1604  in an embodiment derives the following electrical parametric measurements and power calculations from information provided by the current sensor  1608  and voltage sensor  1612 : AC voltage per phase or branch, AC current per phase or branch, per-phase current sensing, active power in watts, apparent power in volt-amps, power factor (PF), accumulated energy in watt-hours (WHr), and other parameters as desired. In one embodiment, the power related metrics are derived in the manner as described above with respect to  FIG. 11 . 
     As described above with respect to sampling and calculations performed when deriving power metrics related to outputs of a PDU, the voltage sensing of the embodiment of  FIG. 17  uses a PT rather than a voltage dropping resistor network. In such an embodiment, sensor phase shifts from the CT and the PT are taken into consideration when performing power calculations. In one embodiment, a CT is used in which the output has a phase shift of about 0.25 degrees, and results in differing power calculation errors depending upon the power factor (PF), with a 0.70 PF resulting in a 0.446% Power calculation error and a 0.95 PF resulting in a 0.144% power calculation error. Similarly, a PT used in an embodiment in which the output has a phase shift of about 0.50 degrees, and results in differing power calculation errors depending upon the power factor (PF), with a 0.70 PF resulting in a 0.894% power calculation error and a 0.95 PF resulting in a 0.291% Power calculation error. 
     In one embodiment, phase shift differences between the CT and PT are compensated, at least partially, through the use of a sampling delay at the ADC, by reading the CT first and then reading the PT. In any event, this embodiment provides a worse case power calculation error of around 0.45%. 
     Power-parametric accuracies, in an embodiment, are as follows: (a) A.C. Voltage (per Phase)—1.0%; (b) A.C. Current (per Phase)—1.0% (c) Active Power (Watts)—2.0%; (d) Apparent Power (VA)—2.0%; (e) Power Factor (PF)—3.0%; (f) Accumulated Energy (Watt Hours) (WHr)—2.0%; and (g) Crest Factor—10%. 
     Per input power sensing is accomplished in PDUs having several different input power configurations. For example, a PDU may have a Delta or Wye input configuration. PDUs may have two or more branches of power outputs that may be separately fused. PDUs also may have two or more input power cords, and combinations of input power cords and branches (e.g. dual corded single phase dual branch). 
       FIG. 18  illustrates a Delta configuration, in which current sensors  1608  are associated with each phase of the Delta configuration, and voltage sensors  1612  are arranged per phase to provide current and voltage information for the outputs  1650  that are associated with a particular phase.  FIG. 19  illustrates a Wye configuration, in which current sensors  1608  are associated with each phase of the Wye configuration, and voltage sensors  1612  are arranged per phase to provide current and voltage information for the outputs  1650  that are associated with a particular phase.  FIG. 20  illustrates a single phase three branch configuration, in which outputs  1650  are arranged on three separate branches. Each branch has a separate current sensor  1608 , and a single voltage sensor  1612  is provided as the voltage across the parallel branches will be the same.  FIG. 21  illustrates a configuration in which two power cords are present, each power cord providing input power for a separate branch of outputs  1650 . Current for each branch is measured at respective current sensors  1608 , and voltage for each branch is measured at respective voltage sensors  1612 .  FIG. 22  illustrates a configuration in which two power cords are present, with each power cord providing input power to two separate branches of outputs  1650 . In such a configuration, voltage sensors  1612  are provided for each power input, and current sensors  1608  are provided for each branch. In each different configuration of the examples of  FIGS. 18-22 , outputs from the current and voltage sensors are provided to the ADC and processing logic and power data per phase or branch may be reported separately or aggregated to provide total power information. 
     With reference now to  FIGS. 23-25 , schematic diagrams of a specific embodiment are described. In this embodiment, a PDU includes current sense components  1800 , and voltage sense components  1818 . As described above, current sense may be accomplished through one or more current transformers. In the embodiment of  FIG. 23 , four current sense channels are provided through inputs  1804  to a printed circuit board. The input from each current transformer is provided across a burden resistor  1808  and a two-pole anti-aliasing filter  1812  to differential current sense inputs  1816  that are provided to a microcontroller. As also described above, voltage sense may be accomplished through one or more potential transformers. In the embodiment of  FIG. 24 , four voltage sense channels are provided through inputs  1820  to the printed circuit board. The input from each potential transformer is provided across a burden resistor  1824  and a two-pole anti-aliasing filter  1828  to differential voltage sense inputs  1832  that are provided to a microcontroller. 
     The voltage sense inputs  1832  and the current sense inputs  1816  are provided to differential inputs  1836 ,  1840 , respectively, of a microcontroller  1844 . The microcontroller  1844 , in this embodiment, is an 8051 microcontroller manufactured by Silicon Laboratories, Inc. In the embodiment of  FIG. 25  microcontroller  1844  is used to provide computations for determining power-related parameters. Microcontroller  1848  is used for communications of input current information to associated displays. An on-sense/frequency sense circuit  1852  provides an indication, for each channel, that may be used for frequency determination and also, in some embodiments, for indicates that power is present at the channel. In other embodiments, similarly as described above, frequency sense provided by circuit  1852  may be used as clock information when power-related parameters are computed. The microcontroller  1844  of this embodiment is connected to an I2C bus  1856  for communications to/from the microcontroller  1844 . A serial port  1858  is present in this embodiment, and may be used for debugging and troubleshooting purposes. Finally, a power supply  1860  is used to provide DC operating power to components on the board; however, a separate 3.0 volt DC power supply (not shown) may be used to provide a reference signal for analog-to-digital conversion. 
       FIG. 26  shows an exemplary environment generally 1000 in which some embodiments of the invention may be practiced. A sentry power manager (SPM)  1002  may be configured for various kinds of user interactions. In the embodiment shown, the SPM is provided as an Internet-based application that communicates with client web browsers  1004 ,  1006  and  1008  through a web server  1010 . The SPM may create, maintain, access and update a database  1012  of tables  1016 ,  1018  and  1020  such as the tables to be described below. The database may be a Microsoft SQL Server database. The SPM may access the database directly or through a daemon/service  1022  that eases any processing burden on the SPM and network traffic to and from the SPM. 
     The daemon/service or the SPM itself may communicate with a simple network management protocol (SNMP) service  1024  and an SNMP trap service  1026 . The SNMP service in turn communicates with one or more power distribution units (PDUs)  1028 ,  1030  and  1032 . 
     The PDUs may comprise, for example, PDUs as described above and distributed by Server Technology, Inc. (STI) of Reno, Nev. A PDU may be monitored and controlled by an electronic control system, of which one example is the Mt. Rose controller board distributed by STI. Each PDU may include one or more electrical outlets and sensors that indicate voltage present at the outlets and current flow through each outlet. Data obtained from the PDUs may be retrieved through the SNMP service and stored in the database. Similarly, data stored in the database may be used to configure or control the PDUs via the SNMP service. Communication protocols other than SNMP, for example XML, could also be used. 
     Messages spawned proactively or reactively by the PDUs may be sent to the daemon service through the SNMP trap service. Or the PDUs may communicate directly with the RMP by a TCP/IP communication protocol 1034 or another communication channel or protocol. 
       FIG. 27  illustrates a method of managing electrical power usage according to the principles of the invention. The method includes collecting  1201  power usage data indicative of electrical current flow through some or all of a plurality of electrical outlets in a PDU or through one or more PDUs, displaying  1203  the power usage data to a user, receiving  1205  a user-initiated command to control current flow through any outlet or PDU selected by the user, and controlling  1207  current flow through the selected outlet or PDU responsive to the command. Controlling current flow through an outlet may be accomplished by turning the outlet on or off  1209 . 
     The method may include receiving  1211  a user-initiated command to reboot control circuitry associated with one or more of the outlets or PDUs and rebooting  1213  the control circuitry responsive to the command. 
     The method may include collecting  1215  environmental data indicative of environmental conditions of the electrical outlets or PDUs and displaying  1217  the environmental data to the user. The environmental data may include temperature or humidity (or both) or other environmental factors as desired. A report descriptive of a power usage trend may be generated  1219  automatically or responsive to a user request. A log of events may be generated  1221 . A message may be automatically sent  1223  to a user if a user-defined event occurs. Such an event may be, for example, sensing of any of a predetermined temperature, a predetermined humidity, or a predetermined amount of electrical power usage by one or more outlets or PDUs. The user may specify the parameters of an event for a one-time report or a report may be sent automatically each time the event occurs. Or an SNMP trap may be used when an event occurs. 
     The method may include assigning  1225  one or more outlets or one or more PDUs in any one location to a cabinet distribution unit (CDU) in that location. At least one unique IP address may be associated  1227  with each location having one or more CDUs. If there are several CDUs at a given location, each may get a separate IP address or a single IP address may be used for some or all of the CDUs at that location. Collecting power usage data respecting an outlet or PDU may be accomplished by communicating via the Internet with the IP address associated with the CDU containing that outlet or PDU. 
     Displaying information to the user may include displaying  1229  the status of one or more CDUs. The status of a CDU may be any of critical, warning, normal, unreachable, or maintenance. “Critical” denotes a condition that may require immediate corrective action. “Warning” denotes a condition that may require attention, for example a parameter has changed since a previous report or display. “Normal” denotes all parameters are within limits that the user may specify or that may have been predetermined at some prior time “Unreachable” indicates a communication failure between the CDU in question and the power manager. “Maintenance” indicates that the CDU in question is being maintained and will remain in that status until manually changed. 
     The method may include displaying  1231   a  graphical representation of locations of CDUs in the power distribution system. This graphical representation may take the form of a world map with indicators such as icons placed over CDU locations. Maps drawn to various scales may be provided; for example, a map of the United States may indicate all CDU locations in that country, a map of Nevada may indicate all CDU locations in Nevada, and a map of Reno may indicate all CDU locations there. 
     The method may include displaying  1233  an amount of electrical power available to a CDU. This may be, for example, the capacity of the electrical feed at a given location, or into the CDU cabinet or into a particular CDU. 
     The method may include grouping or clustering  1235  a plurality of outlets or PDUs. This includes assigning a plurality of outlets or PDUs in a CDU having one IP address and a plurality of outlets or PDUs in a CDU having another IP address to a cluster. Once this has been done, various ones of the above-described steps may conveniently be applied to all outlets or PDUs in the cluster. For example, the status of the cluster may be displayed, a user-initiated command to control current flow through any or all outlets or PDUs in a cluster selected by the user may be received, and current flow through any or all outlets or PDUs in the user-selected cluster may be controlled responsive to the command. 
     Typically, some or all outlets and PDUs have their own current sensor. A voltage sensor is provided for individual outlets or PDUs or banks of outlets and PDUs as needed. Data gathered by these sensors may be used locally, for example to calculate power consumption, which information is thereupon transmitted to the SPM  1002  (see  FIG. 1 ) or the sensor data may be transmitted directly to the SPM. 
     Tables that may be used in embodiments of the invention will now be described. These tables may include, for example, SYSTEM tables, TOWER tables, INFEED tables, OUTLET tables, ENVMON tables, TEMPHUMID tables, CONTACTCLOSURE tables, STATUS LOOKUP tables, SNMP OID LOOKUP tables, OUTLET CLUSTER tables, TRENDING tables, USERS tables, DISCOVERY tables, GRAPHICAL DISPLAY tables, ALERT tables and REPORT tables. Throughout the following discussion of tables, any reference an outlet may refer instead to a PDU or a group of PDUs, and any table directed to characteristics or parameters of individual outlets may instead be directed to characteristics or parameters of one or more PDUs. 
     A SYSTEM table may represent the highest level in a hierarchy. This table may contain system-wide information such as the name and IP address of an entire system. Table 1 is an exemplary system table: 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 MRSystem Table 
               
            
           
           
               
               
               
            
               
                 FIELD NAME 
                 Description 
                 How Obtained 
               
               
                   
               
               
                 MRSYSTEMID 
                 Primary Key 
                 Generated 
               
               
                   
                   
                 when added 
               
               
                 MRSYSTEM_NAME 
                 User Assigned Name 
                 From SNMP 
               
               
                   
                   
                 GET or from 
               
               
                   
                   
                 User entry 
               
               
                 MRSYSTEM_IP_TYPE 
                 IP type - 0 = IPV4, 
                 Defaults to 0 
               
               
                   
                 1 = IPV6 
               
               
                 MRSYSTEM_IPADDR 
                 System IP address 
                 From device 
               
               
                   
                   
                 discovery or 
               
               
                   
                   
                 from User entry 
               
               
                 MRSYSTEM_TCPIP_PORT 
                 include for future 
                 Defaults to 161 
               
               
                   
                 expansion 
               
               
                 MRSYSTEM_LOCATION 
                 User defined location 
                 From SNMP 
               
               
                   
                 string 
                 GET or from 
               
               
                   
                   
                 User entry 
               
               
                 MRSYSTEM_CONTACT 
                 User specified 
                 From SNMP 
               
               
                   
                 system contact 
                 GET or from 
               
               
                   
                   
                 User entry 
               
               
                 MRSYSTEM_DESCR 
                 User specified 
                 From SNMP 
               
               
                   
                 system description 
                 GET or from 
               
               
                   
                   
                 User entry 
               
               
                 MRSYSTEM_WATTS_PER_UNIT_AREA 
                 System calculated 
                 From SNMP 
               
               
                   
                 value 
                 Poll 
               
               
                 MRSYSTEM_AREA 
                 User specified area 
                 From SNMP 
               
               
                   
                 powered by this 
                 GET or from 
               
               
                   
                 system 
                 User entry 
               
               
                 MRSYSTEM_TOTAL_POWER 
                 Total power being 
                 From SNMP 
               
               
                   
                 used 
                 poll 
               
               
                 MRSYSTEM_ENV_MON_COUNT 
                 Number of 
                 From SNMP 
               
               
                   
                 environmental 
                 GET 
               
               
                   
                 monitors on this 
               
               
                   
                 system 
               
               
                 MRSYSTEM_TOWER_COUNT 
                 Number of towers on 
                 From SNMP 
               
               
                   
                 this system 
                 GET 
               
               
                 MRSYSTEM_NIC_SERIALNUMBER 
                 Network interface 
                 From SNMP 
               
               
                   
                 card serial number 
                 GET 
               
               
                 MRSYSTEM_VERSION 
                 Firmware version on 
                 From SNMP 
               
               
                   
                 this system 
                 GET 
               
               
                 MRSYSTEM_SNMP_PUBLIC 
                 The SNMP public 
                 User entered or 
               
               
                   
                 access string - default 
                 from discovery 
               
               
                   
                 to “PUBLIC” 
                 tables 
               
               
                 MRSYSTEM_SNMP_PRIVATE 
                 The SNMP private 
                 User entered or 
               
               
                   
                 access string - default 
                 from discovery 
               
               
                   
                 to “PRIVATE” 
                 tables 
               
               
                 Icon 
                 Not Used 
                 Not Used 
               
               
                 DisplayMapID 
                 Not Used 
                 Not Used 
               
               
                 XLoc_Level1 
                 Not Used 
                 Not Used 
               
               
                 YLoc_Level1 
                 Not Used 
                 Not Used 
               
               
                 Status_Change_Time 
                 Timestamp of last 
                 System derived 
               
               
                   
                 update to the device 
               
               
                 Status_Critical 
                 Number of critical 
                 System derived 
               
               
                   
                 alarms this CDU has 
               
               
                 Status_Warning 
                 Number of warning 
                 System derived 
               
               
                   
                 alarms this CDU has 
               
               
                 Status_Unreachable 
                 Flag whether this 
                 System derived 
               
               
                   
                 CDU is unreachable 
               
               
                   
                 or not 
               
               
                 Status_Maintenance 
                 Flag whether this 
                 System derived 
               
               
                   
                 CDU is in 
               
               
                   
                 maintenance mode or 
               
               
                   
                 not 
               
               
                 Current_Val 
                 This systems highest 
                 System derived 
               
               
                   
                 current reading 
               
               
                 Power_Val 
                 This systems highest 
                 System derived 
               
               
                   
                 power reading 
               
               
                 Temp_Val 
                 This systems highest 
                 System derived 
               
               
                   
                 temperature reading 
               
               
                 Humid_Val 
                 This systems highest 
                 System derived 
               
               
                   
                 humidity reading 
               
               
                 Snooze_Start 
                 Time this system has 
                 User assigned 
               
               
                   
                 gone into 
               
               
                   
                 maintenance mode 
               
               
                 Snooze_End 
                 Time this system will 
                 User assigned 
               
               
                   
                 leave maintenance 
               
               
                   
                 mode 
               
               
                 RackID 
                 Link to the Racks 
                 Assigned by an 
               
               
                   
                 table 
                 admin on the 
               
               
                   
                   
                 GUI 
               
               
                 MRSystem_Cap 
                 System capacity of 
                 Entered via the 
               
               
                   
                 Watts per area unit 
                 Admin on the 
               
               
                   
                   
                 GUI 
               
               
                 MRSystem_Area_Unit 
                 Area unit used to 
                 SNMP Get 
               
               
                   
                 derive system 
               
               
                   
                 capacity 
               
               
                 MRSystem_PowerFactor 
                 The power factor used 
                 SNMP Get 
               
               
                   
                 in power calculations 
               
               
                   
                 performed by the 
               
               
                   
                 system. 
               
               
                   
               
            
           
         
       
     
     Note that most of the fields in this table may be populated via SNMP GETs. For the fields that can be either SNMP specified or user specified, the SPM may attempt to get the value via SNMP when the device is discovered. If unable, no value or a user specified value can be used. When the user specifies a value, an attempt will be made to set the new value on the actual system, but the value in the table is the overriding value if the value on the system differs from the value on the device. Values that are retrieved only via an SNMP GET are not settable by the user, since they are hardware configuration values from the system. The values that are retrieved via an SNMP Poll are dynamic values that may change as the system is used. The polling operations may occur as the data is required by the SPM (e.g., as the data is required by a graphical user interface (GUI) of the SPM), and the polling data may or may not be saved in the database (the labels may remain in the database for OID table lookup reasons). Much of the data retrieved via SNMP Poll operations may be stored in a TREND table for purposes of a trending feature. That is, data may be stored in a TREND table for the purpose of monitoring data trends, viewing or printing reports, or taking appropriate action based on a trend. 
     The SYSTEM table may have a one-to-many relationship with the TOWER, ENVIRONMENTAL MONITOR, CONTACT CLOSURE, TEMPERATURE/HUMIDITY PROBE, INFEED and OUTLET tables/devices in the system. In one embodiment, all of the children (tables) of a SYSTEM table contain the primary key of their SYSTEM table. This characteristic may be true of the tables in several portions of the database, including the SYSTEM tables, TOWER tables, INFEED tables, OUTLET tables, and ENVMON tables. As a result, the entire system may be described by queries that request the parent&#39;s primary key. The SNMP public and private access strings may be included in the system table. These values can be set by the user and may correspond to strings in the controller board firmware. The DISCOVERY tables may contain the strings to use, and these fields may be initially set from these values. 
     Additional fields may be added to a SYSTEM table to support GUI functions such as the display of custom graphics (e.g., icons, schematics or photos representing managed devices or device groups). 
     An exemplary TOWER table will now be described. A tower may be a PDU or other device having a processor such as an ARM processor. One or a plurality of towers may exist within a system. Table 2 shows an exemplary TOWER table. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Mt. Rose TOWER table 
               
            
           
           
               
               
               
            
               
                 FIELD NAME 
                 Description 
                 How Obtained 
               
               
                   
               
               
                 MRTOWERID 
                 Primary Key 
                 Generated 
               
               
                   
                   
                 when added 
               
               
                 MRTOWER_NAME 
                 User Assigned Name 
                 From SNMP 
               
               
                   
                   
                 GET or from 
               
               
                   
                   
                 User entry 
               
               
                 MRTOWER_ABS_NAME 
                 System Generated with the 
                 From SNMP 
               
               
                   
                 first tower, for example, being 
                 GET 
               
               
                   
                 A, the second B, etc. All 
               
               
                   
                 towers have a unique absolute 
               
               
                   
                 name, which may be the 
               
               
                   
                 system IP address appended 
               
               
                   
                 with the absolute name 
               
               
                 MRSYSTEMID 
                 Primary key of the system 
                 Determined 
               
               
                   
                 table to which this tower 
                 when added 
               
               
                   
                 belongs 
               
               
                 MRTOWER_CAPABILITIES 
                 A 4 byte bit map with each bit 
                 SNMP GET 
               
               
                   
                 corresponding to a capability 
               
               
                 MRTOWERSTATUSID 
                 Primary key into a tower status 
                 SNMP POLL 
               
               
                   
                 table which contains strings 
               
               
                   
                 corresponding to the tower 
               
               
                   
                 status 
               
               
                 MRTOWER_INFEED_COUNT 
                 Number of INFEEDS 
                 SNMP GET 
               
               
                   
                 associated with this tower 
               
               
                 MRTOWER_PRODUCT_SN 
                 Tower serial number 
                 SNMP GET 
               
               
                 MRTOWER_MODEL_NUMBER 
                 Tower Model number 
                 SNMP GET 
               
               
                 Icon 
                 Not Used 
                 Not Used 
               
               
                 DisplayMapID 
                 Not Used 
                 Not Used 
               
               
                 XLoc_Level1 
                 Not Used 
                 Not Used 
               
               
                 YLoc_Level1 
                 Not Used 
                 Not Used 
               
               
                   
               
            
           
         
       
     
     The term “Mt Rose” refers to one embodiment of a device embodying portions of the invention. In this embodiment, Mt. Rose refers to the combination of hardware and firmware that are used to implement features described hereon. Such hardware and firmware are included within a PDU, and may provide communications to/from the PDU, perform various calculations, transmit commands to switched outlets, etc. Such functionality may be incorporated in hardware, firmware, software, or any suitable form. 
     As with the SYSTEM table, most of the fields in the TOWER table may be populated via SNMP. For the fields that can be either SNMP specified or user specified, the SPM may attempt to get the value via SNMP when the device is discovered. If unable, no value or a user specified value may be used. When the user specifies a value, an attempt may be made to set the new value on the actual tower, but the value in the table may override the value if the value in the TOWER table differs from the value on the tower. The values that are only retrieved via an SNMP GET are not settable by the user since they are hardware configuration values from the tower. The values that are retrieved via an SNMP Poll are dynamic values that may change as the system is used. The polling operations will occur as the data is required by the SPM (or its GUI), and the polling data may or may not be saved in the database (the labels may remain in the database for OID table lookup reasons). Much of the data retrieved via SNMP Poll operations may be stored in a TREND table for use with a trending feature. 
     A TOWER table has a one-to-one relationship with a SYSTEM table. The primary key of the associated SYSTEM table may be held in the TOWER table. A TOWER table may have a one-to-may relationship with INFEED and OUTLET tables/devices. The INFEEDS associated with a TOWER can be retrieved with a query of the INFEED table using the TOWERID primary key as the search key. Additional fields may be added to a TOWER table to support GUI functions such as the display of custom graphics. 
     An “infeed” is a power input, such as a connection to a power source. A tower may have one or multiple infeeds. Table 3 provides an example of an INFEED table. 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Mt. Rose INFEED Table 
               
            
           
           
               
               
               
            
               
                 FIELD NAME 
                 Description 
                 How Obtained 
               
               
                   
               
               
                 MRINFEEDID 
                 Primary Key 
                 Generated 
               
               
                   
                   
                 when added 
               
               
                 MRINFEED_NAME 
                 User Assigned Name 
                 From SNMP 
               
               
                   
                   
                 GET or from 
               
               
                   
                   
                 User entry 
               
               
                 MRINFEED_ABS_NAME 
                 System Generated - may 
                 From SNMP 
               
               
                   
                 be a concatenation of the 
                 GET 
               
               
                   
                 TOWER absolute name 
               
               
                   
                 and the number of the 
               
               
                   
                 infeed. The first infeed on 
               
               
                   
                 the first tower, for 
               
               
                   
                 example, may be AA, the 
               
               
                   
                 second may be AB. The 
               
               
                   
                 first infeed on the second 
               
               
                   
                 tower may be BA, the 
               
               
                   
                 second may be BB etc. 
               
               
                   
                 All infeeds have a unique 
               
               
                   
                 absolute name that may be 
               
               
                   
                 the system IP address 
               
               
                   
                 appended with the 
               
               
                   
                 absolute name 
               
               
                 MRTOWERID 
                 Primary key of the tower 
                 Determined 
               
               
                   
                 table to which this infeed 
                 when added 
               
               
                   
                 belongs 
               
               
                 MRSYSTEMID 
                 Primary key of the system 
                 Determined 
               
               
                   
                 table to which this infeed 
                 when added 
               
               
                   
                 belongs 
               
               
                 MRINFEED_CAPABILITIES 
                 A 4 byte bit map with 
                 SNMP GET 
               
               
                   
                 each bit corresponding to 
               
               
                   
                 a capability 
               
               
                 MRINFEEDSTATUSID 
                 Primary key into an infeed 
                 SNMP POLL 
               
               
                   
                 status table which 
               
               
                   
                 contains strings 
               
               
                   
                 corresponding to the 
               
               
                   
                 infeed status 
               
               
                 MRINFEEDLOADSTATUSID 
                 Primary key into an infeed 
                 SNMP POLL 
               
               
                   
                 status table which contains 
               
               
                   
                 strings corresponding to 
               
               
                   
                 the infeed load status 
               
               
                 MRINFEED_LOAD_VALUE 
                 Infeed load as determined 
                 SNMP POLL 
               
               
                   
                 by the SNMP poll 
               
               
                 MRINFEED_LOAD_HIGH_THRESH 
                 The SNMP load high 
                 SNMP GET 
               
               
                   
                 threshold on the infeed. 
               
               
                   
                 This value can be set by 
               
               
                   
                 user input to the SPM 
               
               
                   
                 using SNMP PUT 
               
               
                   
                 processing. 
               
               
                 MRINFEED_OUTLET_COUNT 
                 Number of outlets 
                 SNMP GET 
               
               
                   
                 associated with this infeed 
               
               
                 MRINFEED_VOLTAGE 
                 Voltage on the infeed as 
                 SNMP POLL 
               
               
                   
                 of the last SNMP poll 
               
               
                 MRINFEED_POWER 
                 Power at the infeed as of 
                 SNMP POLL 
               
               
                   
                 the last SNMP poll 
               
               
                 MRlnfeed_Capacity 
                 The load capacity of the 
                 SNMP POLL 
               
               
                   
                 input feed. 
               
               
                 Icon 
                 Not Used 
                 Not Used 
               
               
                 DisplayMapID 
                 Not Used 
                 Not Used 
               
               
                 XLoc_Level1 
                 Not Used 
                 Not Used 
               
               
                 YLoc_Level1 
                 Not Used 
                 Not Used 
               
               
                 MRInfeed_ApparentPower 
                 The apparent power 
                 SNMP POLL 
               
               
                   
                 consumption of the input 
               
               
                   
                 feed. 
               
               
                 MRInfeed_PowerFactor 
                 The power factor of the 
                 SNMP POLL 
               
               
                   
                 input feed. 
               
               
                 MRInfeed_CrestFactor 
                 The crest factor for the 
                 SNMP POLL 
               
               
                   
                 load of the input feed. 
               
               
                   
               
            
           
         
       
     
     As with the previously-described tables, most of the fields in this table may be populated via SNMP. For the fields that can be either SNMP specified or user specified, the RDCM may attempt to get the value via SNMP when the device is discovered. If unable, no value or a user specified value may be used. When the user specifies a value, an attempt may be made to set the new value on the actual infeed. If the value to be set is the MRINFEED_LOAD HIGH THRESH, the value must be successfully set on the infeed in order for it to take affect. This is because this value is an SNMP threshold for traps that are recognized and generated by the device firmware. Other values in the table may override the firmware values if the value in the INFEED table differs from the value on the actual infeed. The values that are only retrieved via an SNMP GET are not settable by the user since they are hardware configuration values from an infeed. The values that are retrieved via an SNMP Poll are dynamic values that may change as the system is used. The polling operations may occur as the data is required by the SPM (or its GUI), and the polling data may or may not be saved in the database (the labels may remain in the database for OID table lookup reasons). Much of the data retrieved via SNMP Poll operations may be stored in a TREND table for use with a trending feature. 
     An INFEED table has a one-to-one relationship with a SYSTEM table and a TOWER table. The primary keys of the associated SYSTEM table and TOWER table may be held in the INFEED table. An INFEED table may have a one-to-may relationship with OUTLET tables or devices. The OUTLETS associated with an INFEED can be retrieved with a query of the OUTLET table, using the INFEED primary key as the search key. Additional fields may be added to an INFEED table to support GUI functions such as the display of custom graphics. An outlet is a power output, such as a connection to a powered (or unpowered) device. A tower may have one or multiple outlets. Table 4 presents an exemplary description of an OUTLET table. 
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 Mt. Rose OUTLET table 
               
            
           
           
               
               
               
            
               
                 FIELD NAME 
                 Description 
                 How Obtained 
               
               
                   
               
               
                 MROUTLETID 
                 Primary Key 
                 Generated 
               
               
                   
                   
                 when added 
               
               
                 MROUTLET_NAME 
                 User Assigned Name 
                 From SNMP 
               
               
                   
                   
                 GET or from 
               
               
                   
                   
                 User entry 
               
               
                 MROUTLET_ABS_NAME 
                 System Generated - may be 
                 From SNMP 
               
               
                   
                 a concatenation of the 
                 GET 
               
               
                   
                 TOWER absolute name, 
               
               
                   
                 the INFEED absolute 
               
               
                   
                 name, and the number of 
               
               
                   
                 the outlet. The first outlet 
               
               
                   
                 on the first tower on the 
               
               
                   
                 first infeed may be AAA, 
               
               
                   
                 the second may be AAB. 
               
               
                   
                 The first outlet on the 
               
               
                   
                 second tower on the second 
               
               
                   
                 infeed on the second tower 
               
               
                   
                 may be BBA, the second 
               
               
                   
                 may be BBB etc. All 
               
               
                   
                 outlets have a unique 
               
               
                   
                 absolute name that may be 
               
               
                   
                 the system IP address 
               
               
                   
                 appended with the absolute 
               
               
                   
                 name 
               
               
                 MRINFEEDID 
                 Primary key of the infeed 
                 Determined 
               
               
                   
                 table to which this outlet 
                 when added 
               
               
                   
                 belongs 
               
               
                 MRTOWERID 
                 Primary key of the tower 
                 Determined 
               
               
                   
                 table to which this outlet 
                 when added 
               
               
                   
                 belongs 
               
               
                 MRSYSTEMID 
                 Primary key of the system 
                 Determined 
               
               
                   
                 table to which this outlet 
                 when added 
               
               
                   
                 belongs 
               
               
                 MROUTLET_CAPABILITIES 
                 A 4 byte bit map with each 
                 SNMP GET 
               
               
                   
                 bit corresponding to a 
               
               
                   
                 capability 
               
               
                 MROUTLETSTATUSID 
                 Primary key into an outlet 
                 SNMP POLL 
               
               
                   
                 status table which contains 
               
               
                   
                 strings corresponding to the 
               
               
                   
                 outlet status 
               
               
                 MROUTLETLOADSTATUSID 
                 Primary key into an outlet 
                 SNMP POLL 
               
               
                   
                 status table which contains 
               
               
                   
                 strings corresponding to the 
               
               
                   
                 outlet load status 
               
               
                 MROUTLET_LOAD_VALUE 
                 Outlet load as determined 
                 SNMP POLL 
               
               
                   
                 by the SNMP poll 
               
               
                 MROUTLET_LOADLOW_THRESH 
                 The SNMP load low 
                 SNMP GET 
               
               
                   
                 threshold on the outlet. This 
               
               
                   
                 value can be set by user 
               
               
                   
                 input to the SPM using 
               
               
                   
                 SNMP PUT processing. 
               
               
                 MROUTLET_LOADHIGH_THRESH 
                 The SNMP load high 
                 SNMP GET 
               
               
                   
                 threshold on the outlet. This 
               
               
                   
                 value can be set by user 
               
               
                   
                 input to the SPM using 
               
               
                   
                 SNMP PUT processing. 
               
               
                 MROUTLETCONTROLSTATEID 
                 Primary key into an outlet 
                 SNMP POLL 
               
               
                   
                 lookup table which contains 
               
               
                   
                 strings corresponding to the 
               
               
                   
                 outlet control state 
               
               
                 MROUTLETCONTROLACTIONID 
                 Primary key into an outlet 
                 - SNMP 
               
               
                   
                 lookup table which contains 
                 POLL 
               
               
                   
                 strings corresponding to the 
               
               
                   
                 outlet control action. 
               
               
                 MRASSET 
                 Not used 
                 Not used 
               
               
                 ICON 
                 Not used 
                 Not used 
               
               
                 DISPLAYMAPID 
                 Not used 
                 Not used 
               
               
                 XLOC_LEVEL1 
                 Not used 
                 Not used 
               
               
                 YLOC_LEVEL1 
                 Not used 
                 Not used 
               
               
                 MROutlet_Power 
                 The active power 
                 SNMP POLL 
               
               
                   
                 consumption of the device 
               
               
                   
                 plugged into the outlet. 
               
               
                 MROutlet_Capacity 
                 The load capacity of the 
                 SNMP POLL 
               
               
                   
                 outlet. 
               
               
                 MROutlet_Voltage 
                 The voltage of the outlet. 
                 SNMP POLL 
               
               
                 MROutlet_ApparentPower 
                 The apparent power 
                 SNMP POLL 
               
               
                   
                 consumption of the device 
               
               
                   
                 plugged into the outlet. 
               
               
                 MROutlet_PowerFactor 
                 The power factor of the 
                 SNMP POLL 
               
               
                   
                 device plugged into the 
               
               
                   
                 outlet. 
               
               
                 MROutlet_CrestFactor 
                 The crest factor for the load 
                 SNMP POLL 
               
               
                   
                 of the device plugged into 
               
               
                   
                 the outlet. 
               
               
                   
               
            
           
         
       
     
     As with the previous tables, most of the fields in the OUTLET table may be populated via SNMP. For the fields that can be either SNMP specified or user specified, the SPM may attempt to get the value via SNMP when the device is discovered. If unable, no value or a user specified value may be used. When the user specifies a value, an attempt may be made to set the new value on the actual outlet device firmware. If the value to be set is the MROUTLET_LOAD HIGH THRESH or MROUTLET_LOADLOW_THRESH, the value must be successfully set on the outlet device firmware in order for it to take effect. This is because these values are SNMP thresholds for traps that are recognized and generated by the device firmware. Other values in the table may override the firmware values if the value in the OUTLET table differs from the value on the actual outlet. The values that are only retrieved via an SNMP GET are not settable by the user since they are hardware configuration values from the OUTLET. The values that are retrieved via an SNMP Poll are dynamic values that may change as the system is used. The polling operations may occur as the data is required by the SPM (or its GUI), and the polling data may or may not be saved in the database (the labels may remain in the database for OID table lookup reasons). Much of the data retrieved via SNMP Poll operations may be stored in a TREND table for use with a trending feature. 
     An OUTLET table has a one-to-one relationship with a SYSTEM table, a TOWER table, and an INFEED table. The primary keys of the associated SYSTEM table, TOWER table, and INFEED table may be held in the OUTLET table. Additional fields may be added to an OUTLET table to support GUI functions such as the display of custom graphics. 
     An ENVMON table may be used for monitor and control of environmental monitoring or control devices in a system, such as a temperature sensor, humidity sensor, water sensor, etc. Table 5 is an exemplary ENVMON table. 
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 ENVMON Table 
               
            
           
           
               
               
               
            
               
                 FIELD NAME 
                 Description 
                 How Obtained 
               
               
                   
               
               
                 MRENVMONID 
                 Primary Key 
                 Generated 
               
               
                   
                   
                 when added 
               
               
                 MRENVMON NAME 
                 User Assigned Name 
                 From SNMP 
               
               
                   
                   
                 GET or from 
               
               
                   
                   
                 User entry 
               
               
                 MRENVMON_ABS NAME 
                 System Generated - for 
                 From SNMP 
               
               
                   
                 example, with the first 
                 GET 
               
               
                   
                 monitor being A, the 
               
               
                   
                 second B, etc. All 
               
               
                   
                 monitors have a unique 
               
               
                   
                 absolute name that may be 
               
               
                   
                 the system IP address 
               
               
                   
                 appended with the 
               
               
                   
                 absolute name 
               
               
                 MRSYSTEMID 
                 Primary key of the system 
                 Determined 
               
               
                   
                 table to which this tower 
                 when added 
               
               
                   
                 belongs 
               
               
                 MRENVMONSTATUSID 
                 Primary key into a monitor 
                 SNMP GET 
               
               
                   
                 status table which contains 
               
               
                   
                 strings corresponding to 
               
               
                   
                 the status 
               
               
                 MRENVMON WATERSENSOR NAME 
                 User assigned name for 
                 SNMP GET or 
               
               
                   
                 the water sensor monitor 
                 user entered 
               
               
                 MRENVMONWATERSENSORSTATUSID 
                 Primary key into a water 
                 SNMP POLL 
               
               
                   
                 sensor monitor status table 
               
               
                   
                 which contains strings 
               
               
                   
                 corresponding to the status 
               
               
                 MRENVMON_ADC NAME 
                 User assigned name for 
                 SNMP GET or 
               
               
                   
                 the analog to digital 
                 user entered 
               
               
                   
                 converter 
               
               
                 MRENVMONADCSTATUSID 
                 Primary key into an ADC 
                 SNMP POLL 
               
               
                   
                 status table which contains 
               
               
                   
                 strings corresponding to 
               
               
                   
                 the status 
               
               
                 MRENVMON_ADC_COUNT 
                 The 8-bit count value from 
                 SNMP POLL 
               
               
                   
                 the analog- to-digital 
               
               
                   
                 converter. A non- negative 
               
               
                   
                 value may indicate the 
               
               
                   
                 digital value retrieved 
               
               
                   
                 from the ADC, and a 
               
               
                   
                 negative value may 
               
               
                   
                 indicate that a digital value 
               
               
                   
                 was not able to be 
               
               
                   
                 retrieved. 
               
               
                 MRENVMON_ADC_LOWTHRESH 
                 SNMP trap low threshold 
                 SNMP GET 
               
               
                 MRENVMON_ADC HIGHTHRESH 
                 SNMP trap high threshold 
                 SNMP GET 
               
               
                 MRENVMONTEMPHUMID_SENSOR_COUNT 
                 The number of 
                 SNMP GET 
               
               
                   
                 temperature/humidity 
               
               
                   
                 sensors on the 
               
               
                   
                 environmental monitor. 
               
               
                 MRENVMON_CONTACTCLOSURE 
                 The number of contact 
                 SNMP GET 
               
               
                 COUNT 
                 closures on the 
               
               
                   
                 environmental monitor. 
               
               
                   
               
            
           
         
       
     
     As with the previous tables, most of the fields in the ENVMON table may be populated via SNMP. For the fields that can be either SNMP specified or user specified, the SPM may attempt to get the value via SNMP when the device is discovered. If unable, no value or a user specified value may be used. When the user specifies a value, an attempt may be made to set the new value on the actual device firmware. If the value to be set is one of the SNMP trap thresholds, the value must be successfully set on the outlet device firmware in order for it to take affect. This is because these values are SNMP thresholds for traps that are recognized and generated by the device firmware. Other values in the table may override the firmware values if the value in the table differs from the value on the actual hardware. The values that are only retrieved via an SNMP GET are not settable by the user since they are hardware configuration values from the Mt. Rose system. The values that are retrieved via an SNMP Poll are dynamic values that may change as the system is used. The polling operations may occur as the data is required by the SPM (or its GUI), and the polling data may or may not be saved in the database (the labels may remain in the database for OID table lookup reasons). Much of the data retrieved via SNMP Poll operations may be stored in a TREND table for use with a trending feature. 
     An ENVMON table has a one-to-one relationship with a SYSTEM table. The primary key of the associated SYSTEM table may be held in the ENVMON table. An ENVMON table may have a one-to-may relationship with TEMPHUMID and CONTACTCLOSURE tables/devices in a system. The monitors associated with an ENVMON table can be retrieved with a query of the associated tables using the ENVMONID primary key as the search key. Additional fields may be added to an ENVMON table to support GUI functions such as the display of custom graphics. 
     Table 6 provides an example of a temperature and humidity monitor (TEMPHUMID) table. 
     
       
         
           
               
             
               
                 TABLE 6 
               
             
            
               
                   
               
               
                 TEMPHUMID table 
               
            
           
           
               
               
               
            
               
                 FIELD NAME 
                 Description 
                 How Obtained 
               
               
                   
               
               
                 MRTEMPHUMIDID 
                 Primary Key 
                 Generated 
               
               
                   
                   
                 when added 
               
               
                 MRTEMPHUMID NAME 
                 User Assigned Name 
                 From SNMP 
               
               
                   
                   
                 GET or from 
               
               
                   
                   
                 User entry 
               
               
                 MRTEMPHUMID_ABS NAME 
                 System Generated - for 
                 From SNMP 
               
               
                   
                 example, as 
                 GET 
               
               
                   
                 a concatenation of the 
               
               
                   
                 ENVMON absolute name and 
               
               
                   
                 the number of the 
               
               
                   
                 TEMPHUMID monitor. The 
               
               
                   
                 first TEMPHUMID monitor on 
               
               
                   
                 the first ENVMON may be A1, 
               
               
                   
                 the second may be A2. The 
               
               
                   
                 first on the second ENVMON 
               
               
                   
                 may be B I, the, second may be 
               
               
                   
                 B2 etc. All TEMPHUMID 
               
               
                   
                 monitors have a unique 
               
               
                   
                 absolute name that may be the 
               
               
                   
                 system IP address appended 
               
               
                   
                 with the absolute name 
               
               
                 MRENVMONID 
                 Primary key for the 
                 Determined 
               
               
                   
                 ENVMON associated with 
                 when added 
               
               
                   
                 this TEMPHUMID monitor 
               
               
                 MRSYSTEMID 
                 Primary key of the system 
                 Determined 
               
               
                   
                 table to which this device 
                 when added 
               
               
                   
                 belongs 
               
               
                 MRTEMPHUMIDSTATUSID 
                 Primary key into a monitor 
                 SNMP POLL 
               
               
                   
                 status table which contains 
               
               
                   
                 strings corresponding to the 
               
               
                   
                 status 
               
               
                 MRTEMPHUMIDTEMPSTATUSID 
                 Primary key into a monitor 
                 SNMP POLL 
               
               
                   
                 status table which contains 
               
               
                   
                 strings corresponding to the 
               
               
                   
                 status 
               
               
                 MRTEMPHUMID_TEMP_VALUE 
                 Temperature value as of the 
                 SNMP POLL 
               
               
                   
                 last SNMP poll in degrees. 
               
               
                 MRTEMPHUMID_TEMP_LOWTHRESH 
                 The temperature low 
                 SNMP GET 
               
               
                   
                 threshold value of the sensor 
               
               
                   
                 in degrees, using the scale 
               
               
                   
                 selected by tempHumidSens 
               
               
                   
                 or TempScale. The default is 
               
               
                   
                 Celsius. 
               
               
                 MRTEMPHUMID_TEMP 
                 The temperature high 
                 SNMP GET 
               
               
                 HIGHTHRESH 
                 threshold value of the sensor 
               
               
                   
                 in degrees, 
               
               
                   
                 using the scale selected by 
               
               
                   
                 tempHumidSensorTempScale. 
               
               
                   
                 The default is Celsius. 
               
               
                 MRTEMPHUMIDHUMIDSTATUSID 
                 Primary key into a monitor 
                 SNMP POLL 
               
               
                   
                 status table which contains 
               
               
                   
                 strings corresponding to the 
               
               
                   
                 status 
               
               
                 MRTEMPHUMID_HUMID VALUE 
                 The humidity measured by the 
                 SNMP POLL 
               
               
                   
                 sensor. A non-negative value 
               
               
                   
                 indicates the measured 
               
               
                   
                 humidity in percentage 
               
               
                   
                 relative humidity. A negative 
               
               
                   
                 value indicates that a 
               
               
                   
                 humidity value was not able 
               
               
                   
                 to be measured. 
               
               
                 MRTEMPHU1V1ID_HUMID 
                 The humidity SNMP trap low 
                 SNMP GET 
               
               
                 LOWTHRESH 
                 threshold value of the sensor 
               
               
                   
                 in percentage relative 
               
               
                   
                 humidity. 
               
               
                 MRTEMPHUMID HUMID 
                 The humidity SNMP high 
                 SNMP GET 
               
               
                 HIGHTHRESH 
                 threshold value of the sensor 
               
               
                   
                 in percentage relative 
               
               
                   
                 humidity. 
               
               
                 MRTEMPHUMIDTEMPSCALEID 
                 Primary key into a table 
                 SNMP GET 
               
               
                   
                 which contains strings 
               
               
                   
                 corresponding to the scale 
               
               
                   
                 used for temperature values. 
               
               
                   
                 The default is Celsius. 
               
               
                   
               
            
           
         
       
     
     As with the previous tables, most of the fields in a TEMPHUMID table are populated via SNMP. For the fields that can be either SNMP specified or user specified, the SPM may attempt to get the value via SNMP when the device is discovered. If unable, no value or a user specified value may be used. When the user specifies a value, an attempt may be made to set the new value on the actual device firmware. If the value to be set is one of the SNMP trap thresholds, the value must be successfully set on the outlet device firmware in order for it to take effect. Other values in the table may override the firmware values if the value in the table differs from the value on the actual hardware. The values that are only retrieved via an SNMP GET are not settable by the user since they are hardware configuration values from the system. The values that are retrieved via an SNMP Poll are dynamic values that may change as the system is used. The polling operations may occur as the data is required by the SPM (or its GUI), and the polling data may or may not be saved in the database (the labels may remain in the database for OID table lookup reasons). Much of the data retrieved via SNMP POLL operations may be stored in a TREND table for use with a trending feature. 
     A TEMPHUMID monitor table has a one-to-one relationship with a SYSTEM table and ENVMON table. The primary keys of the associated SYSTEM table and ENVMON table may be held in the TEMPHUMID table. Additional fields may be added to a TEMPHUMID table to support GUI functions such as the display of custom graphics. 
     Table 7 provides an exemplary CONTACTCLOSURE monitor table, which may be used for the monitor and control of contact closures, such as cabinet closures, water contact sensors, or other devices. 
     
       
         
           
               
             
               
                 TABLE 7 
               
             
            
               
                   
               
               
                 CONTACTCLOSURE table 
               
            
           
           
               
               
               
            
               
                 FIELD NAME 
                 Description 
                 How Obtained 
               
               
                   
               
               
                 MRCONTACTCLOSUREID 
                 Primary Key 
                 Generated when 
               
               
                   
                   
                 added 
               
               
                 MRCONTACTCLOSURE NAME 
                 User Assigned Name 
                 From SNMP 
               
               
                   
                   
                 GET or from 
               
               
                   
                   
                 User entry 
               
               
                 MRCONTACTCLOSRE_ABS 
                 System Generated - for 
                 From SNMP 
               
               
                 NAME 
                 example, a concatenation of 
                 GET 
               
               
                   
                 the ENVMON absolute 
               
               
                   
                 name and the number of the 
               
               
                   
                 CONTACTCLOSURE 
               
               
                   
                 monitor. The first monitor 
               
               
                   
                 on the first ENVMON may 
               
               
                   
                 be A1, the second may be 
               
               
                   
                 A2. The first on the second 
               
               
                   
                 ENVMON may be B1, the 
               
               
                   
                 second may be B2 etc. All 
               
               
                   
                 monitors have a unique 
               
               
                   
                 absolute name that may be 
               
               
                   
                 the system IP address 
               
               
                   
                 appended with the absolute 
               
               
                   
                 name 
               
               
                 MRENVMONID 
                 Primary key for the 
                 Determined 
               
               
                   
                 ENVMON associated with 
                 when added 
               
               
                   
                 this monitor 
               
               
                 MRSYSTEMID 
                 Primary key of the system 
                 Determined 
               
               
                   
                 table to which this device 
                 when added 
               
               
                   
                 belongs 
               
               
                 MRCONTACTCLOSURESTATUSID 
                 Primary key into a monitor 
                 SNMP POLL 
               
               
                   
                 status table which contains 
               
               
                   
                 strings corresponding to the 
               
               
                   
                 status 
               
               
                   
               
            
           
         
       
     
     A series of database tables may serve as STATUS LOOKUP tables. These tables allow the SPM application to easily determine the meaning of status returned for devices via SNMP polling. These tables use the status value returned as an index into a table, with the corresponding table record containing a text message, icon or other status indicator associated with the obtained status. 
     To facilitate SNMP processing, an OID LOOKUP TABLE may be created in the SQL SERVER database. This table may have, as one field, the label of the field in a table for which the value is retrieved via SNMP. A second field in the table entry may be the SNMP OID that is used to retrieve the value for the field corresponding to the label. For example, one entry in the MR_SNMP_OID_LOOKUP table may have a DATA LABEL field of MRSYSTEM AREA. That value is a label in the MRSYSTEM table that contains the area controlled by the system. The second field in the MR_SNMP_OID_LOOKUP table (the SNMP_OID field) may contain, for example, the value .1.3.6.1.4.1.1718.3.1.7, which would be the SNMP OID that is used to retrieve this value from the controller board firmware. 
     An outlet cluster is a group of outlets that can be assigned a name, which name can be used by an administrator to assign a user access to several outlets in one operation. This feature is implemented, in one embodiment, using three tables. The first table is the OUTLET CLUSTER table as shown in Table 8. 
     
       
         
           
               
             
               
                 TABLE 8 
               
             
            
               
                   
               
               
                 OUTLET CLUSTER table 
               
            
           
           
               
               
               
            
               
                 FIELD NAME 
                 Description 
                 How Obtained 
               
               
                   
               
               
                 OUTLETCLUSERID 
                 Primary Key 
                 Assigned when 
               
               
                   
                   
                 added 
               
               
                 OUTLET_CLUSER NAME 
                 Text String Cluster 
                 User Input (GUI) 
               
               
                   
                 Name 
               
               
                   
               
            
           
         
       
     
     The OUTLET CLUSTER table contains the name(s) of user-defined outlet clusters. Entries to this table are made when an administrator creates an outlet cluster. 
     The second table is the USER_OUTLETCLUSTER_ACCESS_LINK table as shown in Table 9. This table may be used to determine which users have access to which outlet clusters. 
     
       
         
           
               
             
               
                 TABLE 9 
               
             
            
               
                   
               
               
                 USER_OUTLETCLUSTER ACCESS LINK table 
               
            
           
           
               
               
               
            
               
                 FIELD NAME 
                 Description 
                 How Obtained 
               
               
                   
               
               
                 USERID 
                 Primary Key of an entry in 
                 Assigned when 
               
               
                   
                 the USERS table 
                 added 
               
               
                 OUTLETCLUSERID 
                 Primary Key of an entry in 
                 Assigned when 
               
               
                   
                 the OUTLET CLUSER table 
                 added 
               
               
                   
               
            
           
         
       
     
     The third table is the OUTCLUSTERS table, of which Table 10 is exemplary. This table may be used to determine which outlets are in which clusters. 
     
       
         
           
               
             
               
                 TABLE 10 
               
             
            
               
                   
               
               
                 OUTLETCLUSTERS table 
               
            
           
           
               
               
               
            
               
                 FIELD NAME 
                 Description 
                 How Obtained 
               
               
                   
               
               
                 OUTLETID 
                 Primary Key of an 
                 Assigned when 
               
               
                   
                 entry in the 
                 added 
               
               
                   
                 OUTLET table 
               
               
                 OUTLETCLUSTERID 
                 Primary Key of an 
                 Assigned when 
               
               
                   
                 entry in the 
                 added 
               
               
                   
                 OUTLET CLUSTER table 
               
               
                   
               
            
           
         
       
     
     TRENDING tables may be used to log historical SNMP polling data. In this manner, a user may monitor data trends, view or print reports, or take appropriate action based on a trend. A user may provide configuration information (in some cases via an initialization or .ini file) to specify how often SNMP polling should occur. 
     USERS tables may be used to specify what users have what authorizations to access data in other tables or change device parameters. 
     DISCOVERY tables may contain specific IP addresses, IP address ranges, or other information that enables an SPM application to discover systems, towers, infeeds, outlets or other devices. 
     GRAPHICAL DISPLAY tables may contain graphics or formatting information that are used to convey (e.g., display) any or all of the data contained in the tables to a user. 
     ALERT tables may contain information such as thresholds at which a user should be alerted that a parameter has changed. ALERT tables may also specify actions to be taken when an alert needs to be generated. 
     REPORT tables may contain formatting information for generating reports. The reports may be based on any or all of the parameters contained in other tables. Some or all of the reports may be configurable. 
     Additional tables that may be used include the following: 
                     TABLE 11                  Discovery_Results table                         FIELD NAME   Description   How Obtained               RESULTID   An ID assigned by the system   System Identity Column       DISCID   Reference to an entry in the   System assigned           discovery work table       IPTYPE   IP address type   From CDU Discovery               process       IPADDR   IP address of the CDU   From CDU Discovery               process       STATUS   Status of the discovery   From CDU Discovery               process       DISCOVER_TIME   Time of discovery   From CDU Discovery               process       TOWER_COUNT   Number of towers found on the   From CDU           CDU       INFEED_COUNT   Number of Infeeds found on the   From CDU           CDU       OUTLET_COUNT   Number of the total outlets found   From CDU           on the CDU       ENVMON_COUNT   Number of the Environmental   From CDU           Monitors found on the CDU       THP_COUNT   Number of the Temperature   From CDU           Humidity Sensors found on the           CDU       CC_COUNT   Number of contact closures found   From CDU           on the CDU                    
This table stores the information of the CDU as it was during the discovery time.
 
                            Discovery_Work table                         FIELD NAME   Description   How Obtained               DISCID   An ID assigned by the system   System Identity Column       INPROGRESS   Status of the progress of the   System assigned           discovery       STARTTIME   Time the discovery started   System assigned       ENDTIME   Time the discovery ended   System assigned       IPSTART   First IP address to start disovering   From Admin user on GUI           on       IPEND   Last IP address to end discovering   From Admin user on GUI           on       IPTYPE   Type of IP address to use for   From Admin user on GUI           discovery       COMM_PUBLIC   Public community string to use for   From Admin user on GUI           discovery       COMM_PRIVATE   Private community string to use for   From Admin user on GUI           discovery       FTP_USERNAME   FTP user name to use to download   From Admin user on GUI           the config binary       FTP_PASSWORD   FTP password to use to download   From Admin user on GUI           the config binary                    
This table stores each user initiated discovery, time it started, time it ended and a status on its progress.
 
                            DisplayMaps table                         FIELD NAME   Description   How Obtained               DISPLAYMAPID   An ID assigned by the system   System Identity Column       MAP_FILE_NAME   Name of the image file on disk   From Admin user on GUI       MAP_LEVEL   Not used   Not used       MAP_PARENT_DISPLAYMAPID   ID of the parent display map   From Admin user on GUI       MAP_NAME   Name of this map or location   From Admin user on GUI       MAP_IMAGE   Not used   Not used       XLOC1   X position on parent map   From Admin user on GUI       YLOC1   Y position on parent map   From Admin user on GUI       WIDTH   Image width in pixels   From Admin user on GUI       HEIGHT   Image height in pixels   From Admin user on GUI                    
This table stores all the information of the enabled locations in the system.
 
                            DisplayMaps_Unused table                         FIELD NAME   Description   How Obtained               DISPLAYMAPID   An ID assigned by the system   System Identity Column       MAP_FILE_NAME   Name of the image file on disk   From Admin user on GUI       MAP_LEVEL   Not used   Not used       MAP_PARENT_DISPLAYMAPID   ID of the parent display map   From Admin user on GUI       MAP_NAME   Name of this map or location   From Admin user on GUI       MAP_IMAGE   Not used   Not used       XLOC1   X position on parent map   From Admin user on GUI       YLOC1   Y position on parent map   From Admin user on GUI       WIDTH   Image width in pixels   From Admin user on GUI       HEIGHT   Image height in pixels   From Admin user on GUI                    
This table stores all the information of the disabled locations in the system.
 
                            Location_OutletCluster_Link table                         FIELD NAME   Description   How Obtained               DisplayMapID   Link to DisplayMaps table   From Admin               user on GUI       OutletClusterID   Link to OutletCluster table   From Admin               user on GUI                    
Links all the locations to outletclusters for ease of filtering
 
                            MREnvMon_Poll_Data table                         FIELD NAME   Description   How Obtained               ID   An ID assigned by the system   System Identity Column       Poll_DateTime   Last timestamp these values were   System assigned           valid       MREnvMonID   Link to MREnvMon table   System assigned       MREnvMon_ADC_Count   ADC count on the CDU   From CDU                    
Stores all of the polling data for Environmental Monitors
 
                            MRInfeed_Poll_Data table                         FIELD NAME   Description   How Obtained               ID   An ID assigned by the   System Identity           system   Column       Poll_DateTime   Last timestamp these   System assigned           values were valid       MRInfeedID   Link to MRInfeed table   System assigned       MRInfeed_Load_Value   Infeed Load on the CDU   From CDU       MRInfeed_Voltage   Infeed Voltage on the CDU   From CDU       MRInfeed_Power   Infeed Power on the CDU   From CDU       WattHours   Calculated Watts used for   System Assigned           this particular data record                    
Stores all the polling data for Infeeds.
 
                            MROutlet_Poll_Data table                         FIELD NAME   Description   How Obtained               ID   An ID assigned by the   System Identity           system   Column       Poll_DateTime   Last timestamp these   System assigned           values were valid       MROutletID   Link to MROutlet table   System assigned       MROutlet_Load_Value   Outlet Load on the CDU   From CDU       WattHours   Calcuated Watts used for   System Assigned           this particular record       MROutlet_Power   Outlet Power on the CDU   From CDU                    
Stores all the polling data for Outlets.
 
                            MRSystem_Poll_Data table                         FIELD NAME   Description   How Obtained               ID   An ID assigned by the system   System Identity Column       Poll_DateTime   Last timestamp these values were   System assigned           valid       MRSystemID   Link to MRSystem table   System assigned       MRSystem_Watts_Per_Unit_Area   Watts per unit area on the CDU   From CDU       MRSystem_Total_Power   Total power on the CDU   From CDU                    
Stores all the polling data for the system table.
 
                            MRTempHumid_Poll_Data table                         FIELD NAME   Description   How Obtained               ID   An ID assigned by the system   System Identity Column       Poll_DateTime   Last timestamp these values were   System assigned           valid       MRTempHumidID   Link to MRTempHumid table   System assigned       MRTempHumid_Temp_Value   Temperature on the CDU   From CDU       MRTempHumid_Humid_Value   Humidity on the CDU   From CDU                    
Stores all the polling data for the temperature humidity probes.
 
                            MRTower_Poll_Data table                         FIELD NAME   Description   How Obtained               ID   An ID assigned by the   System Identity           system   Column       Poll_DateTime   Last timestamp these   System assigned           values were valid       MRTowerID   Link to MRTower table   System assigned       MRTowerStatusID   Tower Status on the CDU   From CDU                    
Stores all the polling data for the towers.
 
                            Racks table                         FIELD NAME   Description   How Obtained               RackID   An ID assigned by the system   System Identity Column       RackName   Name of the Rack or Cabinet   From Admin user on GUI       Rack_Parent_DisplaymapID   Link to the DisplayMaps table   From Admin user on GUI       XLoc1   X Position of cabinet on the parent   From Admin user on GUI           map       YLoc1   Y Position of cabinet on the parent   From Admin user on GUI           map       Total_Sq_Ft   Total Square feet this cabinet   From Admin user on GUI           represents       Slots   Number of slots or (Units) this   From Admin user on GUI           cabinet has                    
Stores all the information about the rack and where it is.
 
                            Settings table                         FIELD NAME   Description   How Obtained               Setting   Name of setting   From Admin user on GUI       Value   Value of the setting   From Admin user on GUI                    
Misc system settings stored here
 
                            SysChange table                         FIELD NAME   Description   How Obtained               Setting   Name of the setting   From Admin user on GUI,               telnet or serial               connections       Value   Value of the setting   From Admin user on GUI,               telnet or serial               connections                    
Misc system settings used by all internal programs stored here.
 
                            T_DisplayView table                         FIELD NAME   Description   How Obtained               ViewID   ID of a view   Configured during install           representation   or external setup process       Description   Name to be used   Configured during install           for the GUI display   or external setup process           for the view       ToolTip   Extra information to   Configured during install           be displayed on a   or external setup process           tooltip       Order   Order of display that   Configured during install           can override normal   or external setup process           sorting                    
List of system views that are supported by the main view screen.
 
                            T_DisplayViewItems table                         FIELD NAME   Description   How Obtained               ViewItemID   ID of the View item   Configured during install               or external setup process       ViewID   Link to the T_DisplayView   Configured during install           table   or external setup process       Description   Text to display on the   Configured during install           legend   or external setup process       Start   Start value of the item   Configured during install           category   or external setup process       End   End value of the item   Configured during install           category   or external setup process       Color   Color this item will be   Configured during install           displayed as   or external setup process       Order   Order of display that can   Configured during install           override normal sorting   or external setup process                    
The categories each system view will use to determine that view&#39;s data measurement will belong to. Each category will indicate a color and text to be displayed to the user.
 
                            T_EnvMonStatus table                                 FIELD NAME   Description   How Obtained                       EnvMonStatusID   ID from CDU MIB   CDU MIB           StatusText   Text of the status   CDU MIB           StatusLevel   Not used yet   Not used yet                        
Environmental Monitor Statuses
 
                            T_ManualAdd table                         FIELD NAME   Description   How Obtained               ManualAddID   An ID assigned by the system   System Identity               Column       IPAddress   IP Address of the CDU   From Admin               user on GUI       Comm_Public   Public community string of the   From Admin           CDU   user on GUI       Comm_Private   Private community string of the   From Admin           CDU   user on GUI       FTP_Username   FTP user name to use to get the   From Admin           config binary off the CDU   user on GUI       FTP_Password   FTP password to use to get the   From Admin           config binary off the CDU   user on GUI                    
A temporary holding place for manually added devices. These entries will be repeatedly submitted to the discovery table until the device is successfully managed.
 
                            T_TowerStatus table                                 FIELD NAME   Description   How Obtained                       TowerStatusID   ID from CDU MIB   CDU MIB           StatusText   Text of the status   CDU MIB           StatusLevel   Not used yet   Not used yet                        
CDU Tower Status Table
 
                            User_Location_Access_Link table                         FIELD NAME   Description   How Obtained               UserID   A link to the Users table where   From Admin           UserGroupID := UserID   user on GUI       DisplayMapID   Link to the DisplayMaps table   From Admin               user on GUI                    
UserGroup Access Restriction Table
 
                            User_Outlet_Access_Link table                         FIELD NAME   Description   How Obtained               UserID   A link to the Users table where   From Admin           UserGroupID := UserID   user on GUI       OutletID   Link to the MROutlet table   From Admin               user on GUI                    
UserGroup Access Restriction Table
 
                            User_OutletCluster_Access_Link table                         FIELD NAME   Description   How Obtained               UserID   A link to the Users table where   From Admin           UserGroupID := UserID   user on GUI       OutletClusterID   Link to the OutletCluster table   From Admin               user on GUI                    
UserGroup Access Restriction Table
 
                            User_Rack_Access_Link table                         FIELD NAME   Description   How Obtained               UserID   A link to the Users table where   From Admin           UserGroupID := UserID   user on GUI       RackID   Link to the Rack table   From Admin               user on GUI                    
UserGroup Access Restriction Table
 
     
       
         
           
               
            
               
                   
               
               
                 User_System_Access_Link table 
               
            
           
           
               
               
               
            
               
                 FIELD NAME 
                 Description 
                 How Obtained 
               
               
                   
               
               
                 UserID 
                 A link to the Users table where 
                 From Admin 
               
               
                   
                 UserGroupID := UserID 
                 user on GUI 
               
               
                 SystemID 
                 Link to the MRSystem table 
                 From Admin 
               
               
                   
                   
                 user on GUI 
               
               
                   
               
            
           
         
       
     
                            Userlogins table                         FIELD NAME   Description   How Obtained               USERLOGINID   An ID assigned   System Identity Column           by the system       USERNAME   The logon name   Created by the Admin               User via the GUI       USERPASSWORD   The logon&#39;s   Updated by the user via           encrypted password   the GUI       USERGROUPID   A link to the   Created by the Admin           Users table where   User via the GUI           UserGroupID :=           UserID       HOMEMAPID   A link to the   GUI via the User           DisplayMaps table                    
All user logons for the system with their preferred home map id and passwords encrypted.
 
                            Users table                         FIELD NAME   Description   How Obtained               USERID   An ID given to   Created by the system           the user group       USERNAME   Really a user   Created by the Admin           group name   User via the GUI       USERCAPABILITIESID   A field to hold   Created by the Admin           any special   User via the GUI           capabilities of           this user group like           permission levels       HOMEMAPID   A link to the   GUI via the user           DisplayMaps table                    
This is the Usergroup table as of version 3.1 with all the user groups and the default home map id in it.
 
                            ActionLog table                         FIELD NAME   Description   How Obtained               ALOGID   An ID given to the user group   Created by the               system       USERNAME   Login name or system name that   System assigned           performed the logged action       ACTION_TIME   Time of the logged action   System assigned       USER_IP   IP address of the user performing   System assigned           the action       ACTION_TYPE   Type of action   System assigned       OBJECT_PK   ID of Object logged   System assigned       OBJECT_TYPE   Type of Object logged   System assigned       ACTION_MSG   Formatted message of the log   System assigned                    
The system and user action logs are stored here.
 
                     TABLE 38                  Keys table                         FIELD NAME   Description   How Obtained               KEY   User software activation key   Created by the Admin               User via the GUI       APPLIED   Timestamp it was applied to the   Created by the Admin           system   User via the GUI                    
A list of all submitted software keys in the system.
 
A list of views is provided in List 1.
 
     
       
         
           
               
             
               
                   
               
               
                 LIST 1 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                   
                 R_CDUByLocation 
               
               
                   
                 R_EnvMons 
               
               
                   
                 R_Towers 
               
               
                   
                 V_AllDisplayMaps 
               
               
                   
                 V_CDUEnvSensors 
               
               
                   
                 V_CDUManagedData 
               
               
                   
                 V_CDUOutlets 
               
               
                   
                 V_CDUOutletsWithSecurity 
               
               
                   
                 V_DisplayViewData 
               
               
                   
                 V_DisplayViewDataWithSecurity 
               
               
                   
                 V_EnvironmentalMonitors 
               
               
                   
                 V_EnvironmentalMonitorsWithSecurity 
               
               
                   
                 V_InfeedPowerByCDUDetailedPerDay 
               
               
                   
                 V_InfeedPowerByCDUDetailedPerMonth 
               
               
                   
                 V_InfeedPowerByCDUDetailedPerYear 
               
               
                   
                 V_InfeedPowerByCDUPerDau 
               
               
                   
                 V_InfeedPowerByCDUPerDay 
               
               
                   
                 V_InfeedPowerByCDUPerMonth 
               
               
                   
                 V_InfeedPowerByCDUPerYear 
               
               
                   
                 V_InfeedPowerByLocationPerDay 
               
               
                   
                 V_InfeedPowerByLocationPerMonth 
               
               
                   
                 V_InfeedPowerByLocationPerYear 
               
               
                   
                 V_InfeedPowerByRackPerDay 
               
               
                   
                 V_InfeedPowerByRackPerMonth 
               
               
                   
                 V_InfeedPowerByRackPerYear 
               
               
                   
                 V_InfeedPowerData 
               
               
                   
                 V_InfeedPowerDataByCDUPerMonth 
               
               
                   
                 V_Items 
               
               
                   
                 V_ItemsWithSecurity 
               
               
                   
                 V_OutletPowerByCDUDetailedPerDay 
               
               
                   
                 V_OutletPowerByCDUDetailedPerMonth 
               
               
                   
                 V_OutletPowerByCDUDetailedPerYear 
               
               
                   
                 V_OutletPowerByCDUPerDay 
               
               
                   
                 V_OutletPowerByCDUPerMonth 
               
               
                   
                 V_OutletPowerByCDUPerYear 
               
               
                   
                 V_OutletPowerByClusterDetailedPerDay 
               
               
                   
                 V_OutletPowerByClusterDetailedPerMonth 
               
               
                   
                 V_OutletPowerByClusterDetailedPerYear 
               
               
                   
                 V_OutletPowerByClusterPerDay 
               
               
                   
                 V_OutletPowerByClusterPerMonth 
               
               
                   
                 V_OutletPowerByClusterPerYear 
               
               
                   
                 V_OutletPowerByLocationPerDay 
               
               
                   
                 V_OutletPowerByLocationPerMonth 
               
               
                   
                 V_OutletPowerByLocationPerYear 
               
               
                   
                 V_OutletPowerByRackPerDay 
               
               
                   
                 V_OutletPowerByRackPerMonth 
               
               
                   
                 V_OutletPowerByRackPerYear 
               
               
                   
                 V_OutletPowerData 
               
               
                   
                 V_OutletPowerDataByClusterPerDay 
               
               
                   
                 V_OutletPowerDataByClusterPerMonth 
               
               
                   
                 V_OutletPowerDataByClusterPerYear 
               
               
                   
                 V_Outlets 
               
               
                   
                 V_Search 
               
               
                   
                 V_SearchCriteria 
               
               
                   
                 V_SymbolList 
               
               
                   
                 V_SystemEditSelect 
               
               
                   
                 V_SYSTEMSTATUS 
               
               
                   
                   
               
            
           
         
       
     
     As described above, a graphical user interface may include one or more depictions of geographical locations to show the locations of various CDUs in a given power distribution system. The interface may further provide photographs of these various locations in whatever degree of detail may be desired by users of the power management system. Such photographs may depict one or more equipment racks including icons to indicate rack status. Both a geographic location and a depiction of a rack may be color-coded or may include a color-coded icon based on status. 
     Information from one or more tables, for example the SYSTEM, TOWER, INFEED and OUTLET tables, may be used to provide a listing of towers or other PDUs, infeeds and outlets associated with a selected rack. For each infeed, outlet, or PDU, a status is provided. Load, voltage and power readings are provided for an infeed. Hyperlinks for turning each outlet ON or OFF, and for REBOOTing, are also provided. The tower, infeed, outlets and PDUs may each be configured with a custom name as specified by a user. 
     A user may view a summary of statuses of various devices in a system. For example, an “alarms” listing may be generated from the tables to show which elements of the system are not in a normal status and to describe the nature of the abnormality. In similar fashion, a user may be provided with a listing of environmental conditions at various ones of the CDUs. 
     A user may also view a listing of clusters together with any desired information about each cluster. As with other listings, a cluster listing may give the user various command options such as “Turn On all outlets in the cluster”, “Turn Off all outlets in the cluster”, “Turn On [or Off] a specified PDU or PDUs” or “Reboot”. 
     Information from the tables, for example the TREND table, may be used to illustrate trends between starting and ending dates and times of interest. The user may select the type of trend data to be viewed, such as temperature, humidity, infeed load, infeed voltage, infeed power, system watts per unit area of a location or a cabinet, or total system power usage. 
     The embodiments described above may be implemented using various software and hardware resources. Typically, however, a power manager such as the SPM  102  and database  112  will be implemented by means of computer-readable program code stored on computer-readable media. The computer-readable media may include, for example, any number or mixture of fixed or removable media (such as one or more fixed disks, random access memories (RAMS), read-only memories (ROMs), or compact discs), at either a single location or distributed over a network. The computer readable code will typically comprise software, but could also comprise firmware or a programmed circuit. 
       FIG. 28  is a block diagram of an exemplary computing system  1500  capable of implementing one or more of the embodiments described and illustrated herein. Computing system  1500  broadly represents any single or multi-processor computing device or system capable of executing computer-readable instructions. Examples of computing system  1500  include, without limitation, workstations, laptops, client-side terminals, servers, distributed computing systems, handheld devices, or any other computing system or device. In its most basic configuration, computing system  1500  may comprise at least one processor  1514  and a system memory  1516 . 
     Processor  1514  generally represents any type or form of processing unit capable of processing data or interpreting and executing instructions. In certain embodiments, processor  1514  may receive instructions from a software application or module. These instructions may cause processor  1514  to perform the functions of one or more of the exemplary embodiments described and illustrated herein. For example, processor  1514  may perform, or be a means for performing, either alone or in combination with other elements, one or more of the identifying, transmitting, receiving, determining, selecting, and using steps described herein. Processor  1514  may also perform, or be a means for performing any other steps, methods, or processes described and illustrated herein. 
     System memory  1516  generally represents any type or form of volatile or non-volatile storage device or medium capable of storing data or other computer-readable instructions. Examples of system memory  1516  include, without limitation, random access memory (RAM), read only memory (ROM), flash memory, or any other suitable memory device. Although not required, in certain embodiments computing system  1500  may comprise both a volatile memory unit (such as, for example, system memory  1516 ) and a non-volatile storage device (such as, for example, primary storage device  1532 , as described in detail below). 
     In certain embodiments, exemplary computing system  1500  may also comprise one or more components or elements in addition to processor  1514  and system memory  1516 . For example, computing system  1500  may comprise a memory controller  1518 , an Input/Output (I/O) controller  1520 , and a communication interface  1522 , each of which may be interconnected via a communication infrastructure  1512 . Communication infrastructure  1512  generally represents any type or form of infrastructure capable of facilitating communication between one or more components of a computing device. Examples of communication infrastructure  1512  include, without limitation, a communication bus (such as an ISA, PCI, PCIe, or similar bus) and a network. 
     Memory controller  1518  generally represents any type or form of device capable of handling memory or data or controlling communication between one or more components of computing system  1500 . For example, in certain embodiments memory controller  1518  may control communication between processor  1514 , system memory  1516 , and I/O controller  1520  via communication infrastructure  1512 . In certain embodiments, memory controller may perform, or be a means for performing, either alone or in combination with other elements, one or more of the steps or features described and illustrated herein, such as identifying, transmitting, receiving, determining, selecting, and using. 
     I/O controller  1520  generally represents any type or form of module capable of coordinating or controlling the input and output functions of a computing device. For example, in certain embodiments I/O controller may control or facilitate transfer of data between one or more elements of computing system  1500 , such as processor  1514 , system memory  1516 , communication interface  1522 , display adapter  1526 , input interface  1530 , and storage interface  1534 . I/O controller  1520  may be used, for example, to perform, or be a means for performing, either alone or in combination with other elements, one or more of the identifying, transmitting, receiving, determining, selecting, and using steps described herein. I/O controller  1520  may also be used to perform, or be a means for performing other steps and features set forth in the instant disclosure. 
     Communication interface  1522  broadly represents any type or form of communication device or adapter capable of facilitating communication between exemplary computing system  1510  and one or more additional devices. For example, in certain embodiments communication interface  1522  may facilitate communication between computing system  1510  and a private or public network comprising additional computing systems. Examples of communication interface  1522  include, without limitation, a wired network interface (such as a network interface card), a wireless network interface (such as a wireless network interface card), a modem, and any other suitable interface. In at least one embodiment, communication interface  1522  may provide a direct connection to a remote server via a direct link to a network, such as the Internet. Communication interface  1522  may also indirectly provide such a connection through, for example, a local area network (such as an Ethernet network), a personal area network, a telephone or cable network, a cellular telephone connection, a satellite data connection, or any other suitable connection. 
     In certain embodiments, communication interface  1522  may also represent a host adapter configured to facilitate communication between computing system  1500  and one or more additional network or storage devices via an external bus or communications channel. Examples of host adapters include, without limitation, SCSI host adapters, USB host adapters, IEEE 1694 host adapters, SATA and eSATA host adapters, ATA and PATA host adapters, Fibre Channel interface adapters, Ethernet adapters, or the like. Communication interface  1522  may also allow computing system  1500  to engage in distributed or remote computing. For example, communication interface  1522  may receive instructions from a remote device or send instructions to a remote device for execution. In certain embodiments, communication interface  1522  may perform, or be a means for performing, either alone or in combination with other elements, one or more of the identifying, transmitting, receiving, determining, selecting, and using steps disclosed herein. Communication interface  1522  may also be used to perform, or be a means for performing other steps and features set forth in the instant disclosure. 
     Computing system  1500  may also comprise at least one display device  1524  coupled to communication infrastructure  1512  via a display adapter  1526 . Display device  1524  generally represents any type or form of device capable of visually displaying information forwarded by display adapter  1526 . Similarly, display adapter  1526  generally represents any type or form of device configured to forward graphics, text, and other data from communication infrastructure  1512  (or from a frame buffer, as known in the art) for display on display device  1524 . 
     Exemplary computing system  1500  may also comprise at least one input device  1528  coupled to communication infrastructure  1512  via an input interface  1530 . Input device  1528  generally represents any type or form of input device capable of providing input, either computer or human generated, to exemplary computing system  1510 . Examples of input device  1528  include, without limitation, a keyboard, a pointing device, a speech recognition device, or any other input device. In at least one embodiment, input device  1528  may perform, or be a means for performing, either alone or in combination with other elements, one or more of the identifying, transmitting, receiving, determining, selecting, and using steps disclosed herein. Input device  1528  may also be used to perform, or be a means for performing other steps and features set forth in the instant disclosure. 
     Exemplary computing system  1500  may also comprise a primary storage device  1532  and a backup storage device  1533  coupled to communication infrastructure  1512  via a storage interface  1534 . Storage devices  1532  and  1533  generally represent any type or form of storage device or medium capable of storing data or other computer-readable instructions. For example, storage devices  1532  and  1533  may be a magnetic disk drive (e.g., a so-called hard drive), a floppy disk drive, a magnetic tape drive, an optical disk drive, a flash drive, or the like. Storage interface  1534  generally represents any type or form of interface or device for transferring data between storage devices  1532  and  1533  and other components of computing system  1510 . 
     In certain embodiments, storage devices  1532  and  1533  may be configured to read from and write to a removable storage unit configured to store computer software, data, or other computer-readable information. Examples of suitable removable storage units include, without limitation, a floppy disk, a magnetic tape, an optical disk, a flash memory device, or the like. Storage devices  1532  and  1533  may also comprise other similar structures or devices for allowing computer software, data, or other computer-readable instructions to be loaded into computing system  1510 . For example, storage devices  1532  and  1533  may be configured to read and write software, data, or other computer-readable information. Storage devices  1532  and  1533  may also be a part of computing system  1510  or may be a separate device accessed through other interface systems. 
     In certain embodiments, the exemplary file systems disclosed herein may be stored on primary storage device  1532 , while the exemplary file-system backups disclosed herein may be stored on backup storage device  1533 . Storage devices  1532  and  1533  may also be used, for example, to perform, or be a means for performing, either alone or in combination with other elements, one or more of the identifying, transmitting, receiving, determining, selecting, and using steps disclosed herein. Storage devices  1532  and  1533  may also be used to perform, or be a means for performing other steps and features set forth in the instant disclosure. 
     Many other devices or subsystems may be connected to computing system  1500 . Conversely, all of the components and devices illustrated need not be present to practice the embodiments described and illustrated herein. The devices and subsystems referenced above may also be interconnected in different ways from that shown. Computing system  1500  may also employ any number of software, firmware, and hardware configurations. For example, one or more of the exemplary embodiments disclosed herein may be encoded as a computer program (also referred to as computer software, software applications, computer-readable instructions, or computer control logic) on a computer-readable medium. The phrase “computer-readable medium” generally refers to any form of device, carrier, or medium capable of storing or carrying computer-readable instructions. Examples of computer-readable media include, without limitation, transmission-type media, such as carrier waves, and physical media, such as magnetic-storage media (e.g., hard disk drives and floppy disks), optical-storage media (e.g., CD- or DVD-ROMs), electronic-storage media (e.g., solid-state drives and flash media), and other distribution systems. 
     The computer-readable medium containing the computer program may be loaded into computing system  1500 . All or a portion of the computer program stored on the computer-readable medium may then be stored in system memory  1516  or in various portions of storage devices  1532  and  1533 . When executed by processor  1514 , a computer program loaded into computing system  1500  may cause processor  1514  to perform, or be a means for performing the functions of one or more of the exemplary embodiments described and illustrated herein. Additionally or alternatively, one or more of the exemplary embodiments described and illustrated herein may be implemented in firmware or hardware. For example, computing system  1500  may be configured as an application specific integrated circuit (ASIC) adapted to implement one or more of the exemplary embodiments disclosed herein. 
       FIG. 29  is a block diagram of an exemplary network architecture  1700  in which client systems  1710 ,  1720 , and  1730  and servers  1740  and  1745  may be coupled to a network  1750 . Client systems  1710 ,  1720 , and  1730  generally represent any type or form of computing device or system, such as exemplary computing system  1610 . Similarly, servers  1740  and  1745  generally represent computing devices or systems, such as application servers or database servers, configured to provide various database services or to run certain software applications. Network  1750  generally represents any telecommunication or computer network; including, for example, an intranet, a wide area network (WAN), a local area network (LAN), a personal area network (PAN), or the Internet. 
     As illustrated, one or more storage devices  1760 ( 1 )-(N) may be directly attached to server  1740 . Similarly, one or more storage devices  1770 ( 1 )-(N) may be directly attached to server  1745 . Storage devices  1760 ( 1 )-(N) and storage devices  1770 ( 1 )-(N) generally represent any type or form of storage device or medium capable of storing data or other computer-readable instructions. In certain embodiments, storage devices  1760 ( 1 )-(N) and storage devices  1770 ( 1 )-(N) may represent network-attached storage (NAS) devices configured to communicate with servers  1740  and  1745  using various protocols, such as NFS, SMB, or CIFS. 
     Servers  1740  and  1745  may also be connected to a storage area network (SAN) fabric  1780 . SAN fabric  1780  generally represents any type or form of computer network or architecture capable of facilitating communication between a plurality of storage devices. SAN fabric  1780  may facilitate communication between servers  1740  and  1745  and a plurality of storage devices  1790 ( 1 )-(N) or an intelligent storage array  1795 . SAN fabric  1780  may also facilitate, via network  1750  and servers  1740  and  1745 , communication between client systems  1710 ,  1720 , and  1730  and storage devices  1790 ( 1 )-(N) or intelligent storage array  1795  in such a manner that devices  1790 ( 1 )-(N) and array  1795  appear as locally attached devices to client systems  1710 ,  1720 , and  1730 . As with storage devices  1760 ( 1 )-(N) and storage devices  1770 ( 1 )-(N), storage devices  1790 ( 1 )-(N) and intelligent storage array  1795  generally represent any type or form of storage device or medium capable of storing data and/or other computer-readable instructions. 
     In certain embodiments, and with reference to exemplary computing system  1617 , a communication interface, such as the communication interface  1632  of  FIG. 17 , may be used to provide connectivity between each client system  1710 ,  1720 , and  1730  and network  1750 . Client systems  1710 ,  1720 , and  1730  may be able to access information on server  1740  or  1745  using, for example, a web browser or other client software. Such software may allow client systems  1710 ,  1720 , and  1730  to access data hosted by server  1740 , server  1745 , storage devices  1760 ( 1 )-(N), storage devices  1770 ( 1 )-(N), storage devices  1790 ( 1 )-(N), or intelligent storage array  1795 . Although the figure depicts the use of a network (such as the Internet) for exchanging data, the embodiments described and illustrated herein are not limited to the Internet or any particular network-based environment. 
     In at least one embodiment, all or a portion of one or more of the exemplary embodiments disclosed herein may be encoded as a computer program and loaded onto and executed by server  1740 , server  1745 , storage devices  1760 ( 1 )-(N), storage devices  1770 ( 1 )-(N), storage devices  1790 ( 1 )-(N), intelligent storage array  1795 , or any combination thereof. All or a portion of one or more of the exemplary embodiments disclosed herein may also be encoded as a computer program, stored in server  1740 , run by server  1745 , and distributed to client systems  1710 ,  1720 , and  1730  over network  1750 . Accordingly, network architecture  1700  may perform, or be a means for performing, either alone or in combination with other elements, one or more of the identifying, transmitting, receiving, determining, selecting, and using steps disclosed herein. Network architecture  1700  may also be used to perform, or be a means for performing other steps and features set forth in the instant disclosure. 
     As detailed above, computing system  1610  or one or more of the components of network architecture  1700  may perform, or be a means for performing, either alone or in combination with other elements, one or more steps of the exemplary methods described and illustrated herein. For example, a computer-implemented method for determining a file set may comprise identifying a file set. The method may also comprise identifying a key file for the file set. A first computing system may comprise the file set. The method may further comprise transmitting a key-file identifier to a second computing system, the key-file identifier identifying the key file. The first computing system may receive the first and second file identifiers from the second computing system. The first file identifier may be associated with a first file-identifier set. The second file identifier may be associated with a second file-identifier set. The key-file identifier may be associated with both the first file-identifier set and the second file-identifier set. The method may comprise determining whether the file set comprises a file identified by the first file identifier, and whether the file set comprises a file identified by the second file identifier. The first computing system may transmit a result of the determination to the second computing system. 
     In certain embodiments, identifying a file set may comprise selecting a file directory, selecting a group of files within a directory, selecting files associated with a computer program, and selecting a plurality of files contained on a file storage device. In an additional embodiment, the key file may be a randomly selected file within the file set. 
     In at least one embodiment, determining a file set may further comprise identifying a set of key files from the file set. The first computing system may comprise the file set. Determining a file set may further comprise transmitting a set of key-file identifiers to the second computing system, wherein each key-file identifier in the set of key-file identifiers identifies a file in the set of key files. The method may also comprise receiving a plurality of file identifiers from the second computing system, wherein each file identifier in the plurality of file identifiers is associated with a different file-identifier set. The first computing system may determine which files identified by the plurality of file identifiers are contained within the file set. 
     In certain embodiments, the key-file identifier may comprise at least one of a file name of the key file, a version number of the key file, and a hash of the key file. The key-file identifier may also comprise a file size of the key file, a name of a directory where the key file is stored on the first computing system, and a system identifier for the first computing system. 
     In additional embodiments, wherein each of receiving the first and second file identifiers, determining whether the file set comprises the files identified by the first and second identifiers, and transmitting the result of the determination may be repeated. The aforementioned steps are repeated until the result provides the second computing system with enough information to identify the file set or the first computing system receives an unknown-file-set indication. In a further embodiment the result of the determination may comprise a system identifier for the first computing system, the key-file identifier, the first file identifier, or the second file identifier. 
     A computer implemented method for determining a file set may comprise receiving a key file identifier from a first computing system, the key file identifier identifying a key file associated with the file set. The second computing system may also identify first and second file-identifier sets associated with the key file. The method further comprises identifying a first file identifier in the first file-identifier set, and identifying a second file identifier in the second file-identifier set. The second computing system may transmit the first and second file identifiers to the first computing system. The method also comprises receiving a result from the first computing system, the result being based on a comparison of the first and second file identifiers with the file set. The second computing system may use the result to identify the file set. 
     In an additional embodiment, a computer implemented method for determining a file set may comprise a file-set database. The file-set database may comprise at least one of a table of file names, a table of file versions, a table of file hashes, a table of file directories, a table of file sets, a table of associations of files to file sets. In certain embodiments, identifying a first and second file identifier for the first and second file identifier set may comprise determining that the first file identifier is not in the second file-identifier set and determining that the second file identifier is not in the first file-identifier set. 
     In certain embodiments, a computer implemented method for determining a file set may further comprise receiving a set of key-file identifiers from the first computing system. The method may also comprise identifying a plurality of file-identifier sets associated with the set of key files, and identifying file identifiers associated with the plurality of file-sets. In a further embodiment, an identifier for the key file may comprise at least one of a file name of the key file, a version number of the key file, a hash of the key file, a file size of the key file, a name of a directory where the key file is stored on the first computing system. In an additional embodiment, the result may comprise a system identifier for the first computing system, the key-file identifier, the first file identifier, the second file identifier. 
     In certain embodiments, wherein identifying the first and second file identifiers for the first and second file set, transmitting the first and second file to the first computing system, and receiving a result is repeated. The aforementioned method is repeated until the result contains enough information to identify the file set or the result contains data that exceeds a file-set-identifier threshold. In a further embodiment the file-set-identifier threshold may comprise a ratio of the number of total file identifiers transmitted to the first computing system. The file-set-identifier threshold may also comprise the number of file sets associated with the key file and a number of transmissions between the first computing system and the second computing system, where the transmissions contain information to identify the file set. In an additional embodiment, an unknown-file-set indication is transmitted to the first computing system. 
     In an additional embodiment, the key-file identifier is transmitted to the first computing system. In a further embodiment, identifying the file set from the result may comprise identifying a file-identifier set containing the identifier for the key file and identifying a file-identifier set containing a file identifier transmitted in the result. 
     In certain embodiments, a computer-readable medium may comprise one or more computer executable instructions that, when executed by a computing system, cause the computing system to identify a file set; identify a key file for the file set, a first computing system comprising the file set; transmit a key-file identifier to a second computing system, the key-file identifier identifying the key file; receive first and second file identifiers from the second computing system, a first file identifier being associated with a first file-identifier set, a second file identifier being associated with a second file-identifier set, and the key-file identifier being associated with both the first file-identifier set and the second file-identifier set; determine at least one of whether the file set comprises a file identified by the first file identifier and whether the file set comprises a file identified by the second file identifier; and transmit a result of the determination to the second computing system. 
     In an additional embodiment, one or more computer-executable instructions, when executed by the computing device, further cause the computing device to identify a set of key files from the file set, the first computing system comprising the file set, transmit a set of key-file identifiers to the second computing system, wherein each key-file identifier in the set of key-file identifiers identifies a file in the set of key files, receive a plurality of file identifiers from the second computing system, wherein each file identifier in the plurality of file identifiers is associated with a different file-identifier set, determine which files identified by the plurality of file identifiers are contained within the file set. 
       FIGS. 1A through 75A  are screen shots and perspective views illustrating by way of example various aspects and features that may be included in different embodiments. Not everything shown in any or all of these screen shots need be present in any particular embodiment. For example,  FIG. 48A  shows a measure of reactance, and this can be either capacitive as shown or inductive, indicating lead or lag of current respecting voltage, and this feature is present in some embodiments but not others. 
     A system architecture that embodies the principles of the invention makes possible the collection of power information at the individual outlet, PDU, CDU, group and cluster level and the placing of this information into a database. 
     Power (for example in kilowatts) and power consumption (for example in kilowatt-hours) can be provided in many different ways, including for example per cabinet, per row of cabinets, per multiple rows of cabinets, per data center or multiple data centers, per device or application, per PDU, or even per outlet. This information is collected over a network and stored within a database, for example as described above. The collection period may be defined by a user. The information can made the subject of a trend analysis, a log, a report, a billing invoice, or the like. The information can be exported to a building management system (BMS) or any other system in a data center environment. 
     The information and control provided by embodiments of the invention can be used, for example, by a data center operator to associate and allocate or trend power data to individual users, departments or applications. Billing can be accomplished per data center, per server owner, per application or even according to the time of day. In an enterprise data center an individual department (for example, the accounting department) can be billed for the cost of their application running within their own datacenter. In a co-location facility, customers call be billed for the power usage of just their devices within a shared rack. An enterprise data center can schedule work according to the cost per kW depending on the time of day. 
     A business entity can measure energy efficiency to meet requirements that may be imposed by government agencies, for example as discussed in Appendices B through G. 
     Monitoring and logging outlet and PDU power data can identify abnormal power supply behavior, so the affected IT assets can be identified for preventive maintenance actions to reduce downtime. For example, a large spike in current draw could be used to inform a user that a power supply has failed or is about to fail. 
     It has been estimated that as many as 20% of all installed servers are under-utilized or not performing active work; embodiments of the invention enables a user to identify these IT assets and turn them off, improving data center utilization and reducing energy costs. Also, the ability to reclaim under-utilized assets has the potential to defer the requirement to construct new data center facilities, significantly reducing capital expenditures. Virtualization applications such as VMWare allow applications to be moved to under-utilized servers, allowing servers to be powered-off in off-peak hours. 
     Efficiency can also be improved by using power consumption data to operate each server at its optimal efficiency (this is sometimes called the “sweet spot”). Current drawn by a server can also indicate that a reboot is required. 
     IT asset information (power, environmental, etc.) can be exported to a building manager, building management system, or third party management software. In a typical data center there are two primary consumers of power: the infrastructure that provides cooling, generators, uninterruptible power, and the like; and the IT assets such as servers, routers, network storage, and the like. To achieve maximum efficiency power data are needed respecting both of these consumers. By collecting and logging all outlet or PDU power data and writing this information to the power manager database, this information can be exported to the building management system or third party management software using an API or communicating directly with BMS via MODBUS, BACnet, or the like. 
     The foregoing subject matter, including the content of some of the appendices, addresses the concept of Power Usage measurements for a data center as a whole. There may be granularity divided between ‘cooling’ and ‘power load’. However, these broad metrics do not allow the data center operator to dig below the surface. 
     The data center operator requires an ability to collect power data (Power Usage measurement) in a very granular manner. For example: by equipment cabinet, by application, by user department, by business unit, and so on. Once this data is available in a granular form, the data center operator can provide reports that may change behavior within department, within business units, etc. 
     Power Usage measurements have been provided by equipment cabinet. Grouping of this data written to the SPM Database as set forth above allows Power Usage report to be generated by groups of servers within a cabinet. Clustering allows this Power Usage data to consolidated by groups of servers across multiple cabinets. And it allows Power Usage to be measured by groups of servers installed in multiple data centers. For example an email service of a large enterprise may embody multiple servers, installed in multiple data centers across the United States or even across the world. 
     The ability to group or cluster Power Usage measurements in the SPM data base provides the data center operator a new level of granularity to measure the Department that owns the email service and to point out through trending and logging how Power Usage can be reduced. 
     PIPS, POPs and SPM are the instrumentation, monitoring tools and recording tools that will permit a data center operator to improve effectiveness at the cabinet level, at the dedicated client server level, at the organization level and at the business unit level. 
       FIGS. 1A through 41A  are screen shots of various aspects and features of embodiments of the invention. 
       FIGS. 42A through 69A  are screen shots and illustrations of various aspects of the invention. These  FIGS. 42A through 69A  depict aspects of managing and consolidating information from CDUs within a large data center or across a plurality of locations. A centralized location to view power and environmental status and a centralized SNMP trap destination are indicated. The phrase “Per Outlet Power Sensing” (“POPS”) refers to the concept of monitoring power consumption at each outlet as discussed above. With an Internet interface, monitoring power consumption at each outlet provides detailed power information and allows grouping of outlets to determine kilowatt consumption per device, group of devices, CDU, or cabinet. Power consumption can also be determined per PDU, rack, rows of racks, an entire data center, or the like by clustering outlet information across multiple IP addresses and CDUs, as discussed above. This can provide consolidated CDU information within a data center or across multiple locations, a centralized location to view power and environmental status, capacity planning, reports and trends, multiple views, auto discovery of all CDU devices, alarm details, an ability to manage CDUs, global or individual outlet control, and logging. 
       FIGS. 70A through 75A  are illustrations of various aspects of the invention. 
     Additionally, in certain other embodiments, generation of power metrics as described above, and internal clocking based on an incoming AC signal, are incorporated into other types of appliances other than computing-related equipment, such as household computer, TV, stereo, or other appliances. Such appliances may use the information to adjust internally based on load or report out problems, power metrics, etc. Such communications may be through a wired or wireless communications interface to a sentry poer manager interconnected, for example, to the smart grid. In some embodiments, the a power supply calculates only some, or none of the above noted metrics, but uses this type of monitoring to take action. 
     In certain embodiments, assets that receive power from a PDU include power supplies having such power measurement and reporting circuitry. The PDU includes a communication interface (wired or wireless) and receives power supply metrics from each unit of supported electronics equipment through the communications link. The PDU can use the metrics or report them to other remote entities. 
     The phrase “Per Outlet Power Sensing” (“POPS”) refers to the concept of monitoring power consumption at each outlet as discussed above. The phrase “Per Input Power Sensing” (“PIPS”) refers to the concept of monitoring power delivered to an input of a PDU as discussed above. With an Internet interface, monitoring power consumption at each input/outlet provides detailed power information and allows the determination of power consumption and other power related metrics per device, group of devices, PDU, or cabinet. Power consumption can also be determined per rack, rows of racks, an entire data center, or the like by clustering power information across multiple IP addresses and PDUs, as discussed above. This can provide consolidated PDU information within a data center or across multiple locations, a centralized location to view power and environmental status, capacity planning, reports and trends, multiple views, auto discovery of all PDU devices, alarm details, an ability to manage PDUs, global or individual outlet control, and logging. 
     In can thus be seen that the preferred and other embodiments in other aspects, provided are a number novel features and advantages including, for example: (a) sensing and output of information related to the current and voltage output to various different components and/or applications; (b) a single chip AC input clock solution, in which a power monitoring circuit or a power meter does not require an external oscillator for a time base; (c) predictive failure of various power components; (d) flagging of anomalous current, voltage, or power usage for a component or a PDU; (e) an accurate energy accumulation scheme for one or more outputs associated with a single power monitoring and metering circuit; (f) output switching capability with relatively low power requirements using switching versus holding transistors in relay circuits used to switch the outputs; (g) output switching at power zero-crossings in the AC power cycle; (h) modular construction of an outlet assembly with options to provide switched outputs or non-switched outputs; (i) the ability to determine is lack of power at an outlet is the result of loss of input power or a blown fuse; and (j) the ability to assess the health of power supplies an installed base of power supplies in data center equipment racks without requiring any modification of the power supplies. 
     Various modifications to the described embodiments will be apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the scope of the invention. It can thus be seen, however, that one or more embodiments described herein may provide one or more among the following features or advantages 
     1) Sensing and outputting information related to the current and voltage input to a PDU or to various different components and applications. 
     2) A single chip AC input clock solution, in which a power monitoring circuit or a power meter does not require an external oscillator for a time base. 
     3) Predictive failure of various power components. 
     4) Flagging of anomalous current, voltage, or power usage for a component or a PDU. 
     5) An accurate energy accumulation scheme for one or more outputs associated with a single power monitoring and metering circuit. 
     6) Output switching capability with relatively low power requirements using switching versus holding transistors in relay circuits used to switch the outputs. 
     7) Output switching at power zero-crossings in the AC power cycle. 
     8) Modular construction of an outlet assembly with options to provide switched outputs or non-switched outputs. 
     9) An ability to determine if lack of power at an outlet is the result of loss of input power or a blown fuse. 
     10) An ability to assess the health of power supplies an installed base of power supplies in data center equipment racks without requiring any modification of the power supplies. 
     11) A PDU with (a) power sensing circuitry that reports one or more of voltage, current or power usage by the PDU or one or more outlets in the PDU and (b) one or more processors that use this information to compute apparent power, RMS power, power factor, and other power related information. 
     12) A PDU having an intelligent power module with a microprocessor and a circuit that senses line frequency of the power input. Clock drift in the microprocessor clock due to temperature fluctuations is corrected using the input power frequency sense. 
     13) A system comprising a power manager and a power distribution unit (PDU), the PDU comprising a plurality of outputs, voltage and current sense circuits, and a power reporting circuit that provides power related information for inputs and outputs of the PDU to the power manager, the power manager receiving the power related information and adjusting the power consumption of the PDU or of one or more components that receive power from the PDU. 
     14) A system comprising a power manager and a PDU, the PDU comprising one or more power reporting circuits that provide power related information for each input and output of the PDU to the power manager, the power manager receiving power related information from two or more PDUs related to an application that is running on two or more components that receive power from the PDUs and compiling this information to determine power-related information for the application. 
     15) A power management system that provides assigning outlets or PDUs in any one location to a cabinet distribution unit in that location. At least one unique IP address may be associated with each location having one or more CDUs. If there are several CDUs at a given location, each may get a separate IP address or a single IP address may be used for some or all of the CDUs at that location. Collecting power usage data respecting an outlet or a PDU may be accomplished by communicating via the Internet with the IP address associated with the CDU containing that outlet. 
     16) A power management system with the ability to collect and provide trends related to PDUs, CDUs, cabinets, and components that receive power from one or in a data center, trends including power, temperature, humidity, and the ability to set triggers if limit thresholds are exceeded. 
     17) A system that provides billing for power consumption for one or more discreet power consuming components, PDUs, CDUs, and cabinets within a data center. 
     18) A power management system that identifies low utilization or non-utilized servers and initiates the shut-down of these servers. 
     19) A power management system that identifies an optimal operating condition for a cabinet, PDU, CDU, or discrete component, such as a server, or a set of components, that receives power from a PDU, and identifies one or more components that are less than optimal. 
     20) A method of managing electrical power including collecting power usage data indicative of electrical current flow through each of a plurality of electrical outlets or PDUs, displaying the power usage data to a user, receiving a user-initiated command to control current flow through any outlet or PDU selected by the user, and controlling current flow through the selected outlet or PDU responsive to the command Controlling current flow through an outlet or PDU may mean turning the outlet or PDU on or off. The user may initiate a command to reboot control circuitry associated with one or more of the outlets or PDUs. Data indicative of environmental conditions, such as temperature and humidity, of the electrical outlets or PDUs may be collected and displayed. A log of events and a report descriptive of a power usage trend may be generated. Outlets and PDUs may be assigned to CDUs and an IP address may be associated with one or more CDUs. A CDU status, for example critical, changed, normal, no data, maintenance, or snooze may be displayed, as may a graphical depiction of locations of CDUs. Available infeed power may be displayed. A message may be sent automatically if a defined event, for example a temperature or humidity level is reached, a set amount of electrical power is used at a location or by one or more CDUs or even a single outlet. 
     21) Outlets or PDUs in different CDUs having different IP addresses may be clustered, thereby allowing a user to view the status of, and to control, all outlets or PDUs in the cluster. 
     22) A power management database structure having one or more of the tables listed above. 
     23) A power and power consumption data can be provided per cabinet, per row of cabinets, per multiple rows of cabinets, per data center or multiple data centers, per device or application, per PDU, per outlet or in any other desired manner. This information can be used for trend analyses, logs, reports, billing invoices, or the like. The information can be exported to a building management system (BMS) or any other system in a data center environment. 
     24) A data center operator can associate and allocate or trend power data to individual users, departments or applications. Billing can be accomplished per data center, per server owner, per application or time of day. An individual department can be billed for the cost of their application. Customers call be billed for the power usage of just their devices within a shared rack. Work can be scheduled according to the cost per kW depending on the time of day. 
     25) A business entity can measure energy efficiency to meet requirements that may be imposed by government agencies. 
     26) Abnormal power supply behavior can be identified. This facilitates preventive maintenance. 
     27) Applications can be moved to under-utilized servers. Virtualization applications such as VM-Ware allow servers to be powered-off in off-peak hours. IT assets not being used can be identified and turned off. The ability to reclaim under-utilized assets can avoid or defer construction of new data center facilities. 
     28) Power consumption data can also be used to help operate each PDU or component at its optimal efficiency and reboot if needed. 
     29) IT asset information (power, environmental, etc.) can be exported to a building manager or building management system, enabling assets to be managed. 
     30) An ability to communicate with other devices (e.g. servers) using tools such as SNMP, XML, iLo or other proprietary protocols to collect power and environmental information from these devices. 
     31) Grouping and clustering information via an IP, across IPs, or across the world to monitor, and manage power and environmental information.