Abstract:
A cryogenic system including a source of cryogen fluid, a cryogenic chamber receiving the cryogen fluid to cool the cryogenic chamber, an exhaust for venting spent cryogen from the cryogenic chamber, a cryogenic sensor positioned in the cryogenic chamber to monitor a condition, and a cryogenic signal conditioning unit associated with the cryogenic sensor. The cryogenic signal conditioning unit includes a software programmable current source, a programmable gain amplifier, an analog to digital converter, a memory, and a user interface.

Description:
BACKGROUND 
       [0001]    The present invention is directed to systems and methods for operation of and data collection related to cryogenic systems. The field of cryogenics involves operating temperatures below negative one-hundred-eighty degrees centigrade (−180 degrees Celsius). These low temperatures present unique and, often, difficult operational environments and typically require specialized equipment and instrumentation. For example, sensors and instrumentation used in cryogenic data collection systems have design parameters that are uniquely suited to the cryogenic operational environments and the careful controls necessary to maintain the cryogenic operational environments. These systems are highly sophisticated and precisely controlled to safely and consistently maintain the cryogenic operational environment. 
         [0002]    Many sensors designed to operate at room temperature include on board signal conditioning. This allows the sensors to provide a robust, easy to measure output, while being driven from a loosely regulated source. Due to the unique operational conditions of maintaining temperatures below 180 degrees Celsius, cryogenic sensors, however, are usually unconditioned, and typically provide a non-robust, hard-to measure output while requiring excitation from a precisely regulated source. 
         [0003]    It would be desirable to have a system and method for handling several challenges in cryogenic data acquisition that is compatible with a variety of data acquisition and control systems. 
       BRIEF SUMMARY OF THE INVENTION 
       [0004]    The present invention overcomes the aforementioned drawbacks by providing a signal conditioning unit that may be connected to a variety of cryogenic sensors and allow the signals from those sensors to be easily read by a data acquisition system. 
         [0005]    In one construction, the invention provides a cryogenic system that includes a source of cryogen fluid, a cryogenic chamber receiving the cryogen fluid to cool the cryogenic chamber, an exhaust for venting spent cryogen from the cryogenic chamber, a cryogenic sensor positioned in the cryogenic chamber to monitor a condition, and a cryogenic signal conditioning unit associated with the cryogenic sensor. The cryogenic signal conditioning unit includes a software programmable current source that outputs an excitation current to the cryogenic sensor. A programmable gain amplifier receives a sensor output from the cryogenic sensor and amplifies the sensor output into an amplified output. An analog to digital converter receives and converts the amplified output, and outputs a data output. A memory is in communication with the software programmable current source, the analog to digital converter, and the programmable gain amplifier. A user interface is in communication with the software programmable current source, the analog to digital converter, the programmable gain amplifier, and the memory. The user interface uses an industry standard communication protocol, the user interface communicates with the software programmable current source to set a value of the excitation current, and the data output is saved to the memory. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0006]    The invention will be better understood and features, aspects and advantages other than those set forth above will become apparent when consideration is given to the following detailed description thereof. Such detailed description makes reference to the following drawings. 
           [0007]      FIG. 1  is a schematic representation of a cryogenic signal conditioning unit according to the invention. 
           [0008]      FIG. 2  is a perspective view of one construction of the cryogenic signal conditioning unit of  FIG. 1 . 
           [0009]      FIG. 3  is a schematic representation of the cryogenic signal conditioning unit of  FIG. 2  with a hall sensor connected. 
           [0010]      FIG. 4  is a schematic representation of the cryogenic signal conditioning unit of  FIG. 2  with a temperature diode connected. 
           [0011]      FIG. 5  is a schematic representation of a cryogenic sensor readout module according to the invention. 
           [0012]      FIG. 6  is a schematic representation of a portion of one construction of the cryogenic sensor readout module of  FIG. 5 . 
           [0013]      FIG. 7  is a schematic representation of another portion of one construction of the cryogenic sensor readout module of  FIG. 5 . 
           [0014]      FIG. 8  is a schematic representation of another portion of one construction of the cryogenic sensor readout module of  FIG. 5 . 
       
    
    
       [0015]    While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0016]    The present invention will be described in terms of one or more preferred embodiments, and it should be appreciated that many equivalents, alternatives, variations, and modifications, aside from those expressly stated, are possible and within the scope of the invention. 
         [0017]      FIG. 1  shows a schematic representation of a cryogenic signal conditioning unit  10  for use with a cryogenic sensor  14 . The cryogenic sensor  14  monitors a condition within a cryogenic chamber  15 . The cryogenic chamber  15  is supplied with a cryogen (e.g., helium or nitrogen) from a cryogen source  16  and includes an exhaust  17 . The flow of the cryogen through the chamber  15  drops the temperature within the chamber  15  to cryogenic temperatures. The cryogenic signal conditioning unit  10  includes a software programmable current source  18 , a programmable gain amplifier  22 , an analog-to-digital converter (A/D converter  26 ), a memory  30 , a microcontroller  34 , and a user interface  38 . 
         [0018]    Many different types of sensors  14  are used in cryogenic conditions. For example, the sensor  14  may be any one of a temperature diode, a thermistor, a thermocouple, an RTD sensor, a hall sensor, and a pressure transducer. The inventive cryogenic signal conditioning unit  10  could be used with other sensor types as desired. The sensors  14  may output a raw sensor output  42  from between about sub-micro volt to volt levels. 
         [0019]    The current source  18  provides the sensor  14  with an excitation current  46  and a value of the excitation current  46  is set according to the specifications of the sensor  14 . Typically, the value of the excitation current  46  is between zero milliamps and two-hundred milliamps (0-200 mA). In one construction, the current source  18  has four manually configurable current ranges: 0-200 mA, 0-20 mA, 0-2 mA, and 0-200 uA. To manually set the range of the excitation current  46 , a user manually moves a jumper  50  to the appropriate position on a set of jumper pins  54 . Alternatively, the excitation current  46  range can be set via software interface as will be discussed below. 
         [0020]    The amplifier  22  receives a raw sensor output  42  from the sensor  14  and converts the sensor output  42  to an amplified output  58 . This amplification increases the sensor output  42  voltage to a more usable amplified output  58  voltage. Various amplification schedules or tables may be used for determining the appropriate gain amplification, as is understood in the art. 
         [0021]    The A/D converter  26  receives the amplified output  58  from the gain amplifier  22  and converts the analog voltage to a data output  62  that is a digital signal that can be used by the cryogenic signal conditioning unit  10 . Various circuits and computations can be used for the conversion, as is known in the art. 
         [0022]    The memory  30  records the data output  62  and makes the stored data output  62  available for data collection or monitoring. In one example, the memory  30  is an EEPROM type of permanent memory. Other memory types may be used, as desired. The memory  30  also stores settings, configurations, ranges, and other data used by elements of the cryogenic signal conditioning unit  10 . 
         [0023]    The microcontroller  34  is in communication with the other components of the cryogenic signal conditioning unit  10  and coordinates there actions. For example, the microcontroller  34  recognizes what type of sensor  14  is connected to the cryogenic signal conditioning unit  10  (e.g., by user input), looks up the corresponding excitation current  46  in a look up table of the memory  30 , and communicates with the current source  18  to provide the desired excitation current  46  to the sensor  14 . Likewise, the microcontroller  34  communicates with the gain amplifier  22  and the A/D converter  26  to maintain the desired operation of the cryogenic signal conditioning unit  10 . 
         [0024]    The user interface  38  communicates with the cryogenic signal conditioning unit  10  and allows the user to communicate with and control the operation of the unit. For example, the user interface  38  could be a personal computer, a human machine interface (HMI), a network, or another interface that allows communication. The user can directly control the operation of the cryogenic signal conditioning unit  10  by setting the sensor type, excitation current  46 , amplification values, and accessing the memory  30 . 
         [0025]    Additionally, the cryogenic signal conditioning unit  10  is arranged to communicate with an external system  66  such as a computer network or the internet, a cryogenic sensor readout module as discussed below, a data collection system, an LCD readout screen, or another device or system, as desired. A communications port  70  or output bus provides connection of the user interface  38  and the external system  66  to the cryogenic signal conditioning unit  10 . Control can be implemented directly to the conditioning unit  10  via the user interface  38  or it can come from remote control via a program or network control. Similarly, control and monitoring can be segregated. For example, many users may be interested in monitoring the condition measured by the sensor  14 , but should not be allowed to adjust the operating parameters of the cryogenic signal conditioning unit. Limited access can be controlled to allow select users write or control access while other users are given only read access. Similarly, the units may be setup to allow control from only one source at a time. 
         [0026]    The cryogenic signal conditioning unit  10  may be configured to communicate with an industry standard protocol. In one construction, the unit communicates with MODBUS. In other constructions, the unit communicates with Ethernet, CAN, or another commonly used protocol. Additionally, one construction of the unit utilizes RS485 connections for sending the communication. Alternative connection types may be used, as desired to provide easy and cost effective communication. 
         [0027]      FIGS. 2-4  show one construction of a cryogenic signal conditioning unit  10  according to the invention. The cryogenic signal conditioning unit  10  includes a housing  74  that defines a connecting feature in the form of a DIN rail slot  78 , a number of indicator LEDS  82 , a power bus  86  for receiving power, an excitation bus  90  for delivering the excitation current  46  to the sensor  14 , a sensor bus  94  for receiving the sensor output  42  from the sensor  14 , and an output bus  98  for sending the data output  62 . Additionally, the cryogenic signal conditioning unit  10  may include different alarm and monitoring busses. The illustrated housing  74  contains the software programmable current source  18 , the A/D converter  26 , the programmable gain amplifier  22 , the memory  30 , and the microcontroller  34 . 
         [0028]    The housing  74  is arranged such that the unit is small and fits easily into a control panel. The DIN rail slot  78  allows for mounting of a number of cryogenic signal conditioning units  10  in a compact space. This compact arrangement is substantially refined when compared to the bulky, complicated, and difficult to implement systems currently available. 
         [0029]    The indicator LEDS  82  can be used for diagnostic purposes to understand how the cryogenic signal conditioning unit  10  is operating at any given time. For example, a fault may show a red LED  82 , normal operation may light a green LED  82 , a power LED may illuminate next to the word power, or other indicators may be used, as desired. 
         [0030]      FIG. 3  shows a typical connection for a hall effect sensor  14  and  FIG. 4  shows a typical connection for a temperature diode. The power bus  86  is illustrated receiving 24 VDC, the output bus  98  is connected to a RS485 device, the excitation bus  90  is connected to the respective sensor  14 , and the sensor bus  94  is connected to the sensor output  42 . 
         [0031]    In operation, the cryogenic signal conditioning unit  10  may be installed into a service panel and connections are made to the sensor  14 , the communications bus  98 , and power bus  86 . The housing  74  is opened and the user moves the jumper  50  to an appropriate position for the sensor  14  such that the excitation current  46  range is correct. Then, the user closes the housing  74 , and accesses the unit  10  via the user interface  38  and sets the sensor  14  type. The excitation current  46  and amplification values are then set automatically. Alternatively, the user can manually set the excitation current  46  and amplification values. The sensor  14  can then be operated and the data output  62  collected. The data output  62  represents the readings of the sensor  14 . 
         [0032]      FIG. 5  shows a schematic representation of a cryogenic sensor readout module  100  according to the invention for use with the sensor  14 . The cryogenic sensor  14  monitors a condition within a cryogenic chamber  15 . The cryogenic chamber  15  is supplied with a cryogen (e.g., helium or nitrogen) from a cryogen source  16  and includes an exhaust  17 . The flow of the cryogen through the chamber  15  drops the temperature within the chamber  15  to cryogenic temperatures. The readout module  100  may be used in conjunction with the cryogenic signal conditioning unit  10  or independent thereof. The following discussion will detail how the readout module  100  may be used independent of the cryogenic signal conditioning unit  10  first, and be followed by a discussion of how the cryogenic signal conditioning unit  10  may be used together with the readout module  100 . 
         [0033]    The readout module  100  includes a printed circuit board  104  that includes a power bus  108  for receiving power, a microcontroller  112 , an excitation bus  116 , a high current port  120 , a general port  124 , and a communications port in the form of an Ethernet port  128 . 
         [0034]    The microcontroller  112  includes a low-noise signal processor  132 , an analog-to-digital converter (A/D converter  136 ), a converter  140 , and an output module  144 . The microcontroller  112  also controls the communication of the readout module  100 , the operation and coordination of the various components, includes a memory, controls signals sent to and from the sensor  14 , and other aspects as will be apparent to those skilled in the art. 
         [0035]    The microcontroller  112  provides an excitation current  148  to the excitation bus  116  which is then passed onto the sensor  14 . The excitation current  148  is set according to the specifications of the type of sensor  14  used. As with the cryogenic signal conditioning unit  10 , the excitation current  148  can be from between about zero milliamps and about two-hundred milliamps (0-200 mA). Other excitation currents may be used, as desired. The excitation current  148  is provided to the excitation bus  116 , where the excitation current  148  is provided to the sensor  14 . 
         [0036]    The sensor delivers a low voltage sensor output  152 . This low voltage is provided to the low-noise signal processor  132  where the sensor output  152  may be amplified, conditioned, filtered, or undergo other conditioning. After the sensor output  152  is processed, the low-noise signal processor  132  outputs a conditioned output  156  to the A/D converter  136  where the conditioned output  156  is converted into a usable digital signal in the form of a data output  160 . The data output  160  is provided to the converter  140  where the data output  160  is calculated into an engineering output  164  according to the sensor  14  type. For example, a temperature diode&#39;s sensor output  152  will be conditioned and converted into an engineering output  164  that reads as a temperature value in degrees Kelvin. The engineering output  164  is then provided to the output module  144  where it may be disseminated to a graphics LCD  168 , the Ethernet port  128 , the general port  124 , or another component of the readout module  100 . 
         [0037]    In one example of the readout module  100 , the output module  144  provides the engineering output  164  to the graphics LCD  168  and shows the user what the sensor  14  is reading. Additionally, the engineering output  164  is provided to a network  172  via the Ethernet port  128  where the user may access the data via a computer connected to the network  172 . A Java™ interface, or other network based program, allows the user to interact with the collected data and use the data. For example, the program could provide the user with a chart showing the engineering output  164  over time. A network  172  based interface provides a controlled and easy to use access mode for the collected engineering output  164 . Further, the readout module  100  can be controlled from the network  172 . Access for read, write, administrative, et cetera rights may be provided to various users depending on their individual access rights. For example, a user with administrative rights may be able to program the readout module  100  for the sensor  14  type, engineering output  164  units, conversion equations, or other control aspects. 
         [0038]    Additionally, a keyboard  176  or other user interface may be directly connected to the readout module  100 . This would allow a user to configure the readout module  100  manually by communicating through the keyboard  176  and the graphics LCD  168 . Further, the high current port  120  can be used to control an external device such as a relay  180 , alarm, or other device. This allows the readout module  100  to control a system dependant on the sensor output  152 . 
         [0039]    The cryogenic signal conditioning unit  10  may also be used with the readout module  100 . For example, the cryogenic signal conditioning unit  10  may communicate a data output  160  to the readout module  100  through the network  172 , or directly. That data output  160  could then be converted to an engineering output  164  and used by the readout module  100 . 
         [0040]      FIGS. 6-8  show one construction of a readout module  100  according to the invention. In the illustrated construction, the readout module  100  can utilize eight sensors  14  and output eight sets of engineering outputs  164 . As shown, the various components of the readout module  100  may be realized on a single chip, multiple chips, multiple circuits, a single circuit, or a single printed circuit board  104 . 
         [0041]    The readout module  100  is intended to provide a small sized component that can be easily integrated into cryogenic systems. The only readout modules currently available are highly complex and difficult to use. This system would make the readout and use of data from cryogenic sensors  14  much more accessible. The readout module  100  meets a long felt need in the area of cryogenics.