Patent Publication Number: US-10331392-B1

Title: Image forming operation monitoring systems and methods

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to U.S. patent application Ser. No. 15/835,760, filed Dec. 8, 2017, which is hereby incorporated by reference in its entirety. 
     BACKGROUND 
     Image forming apparatuses have become increasingly proficient at performing various operations, such as printing, copying, scanning, or faxing operations. To determine whether a new image forming apparatus is performing operations more quickly than previously designed devices, or whether an existing image forming apparatus is continuing to perform up to desired standards, the image forming apparatus may be monitored as it performs operations. 
     In some cases, image forming apparatuses may alert another device of an operational status of the image forming apparatus to indicate that it has performed, or is performing, an operation. However, not all image forming apparatuses are configured to supply such information, and different devices may supply this information in different ways, or at different times. 
     SUMMARY 
     In a first aspect, a method is provided. The method includes receiving, by an image forming apparatus, instructions to execute an operation of the image forming apparatus. The method further includes, in response to receiving the instructions, executing, by the image forming apparatus, the operation. The method yet further includes detecting, by an external sensor circuit, a status of an operational parameter of the image forming apparatus indicative of the image forming apparatus executing the operation. The method additionally includes sending, by the external sensor circuit, notifications of the status of the operational parameter to a host computing device. The method also includes generating, in response to receiving the notifications of the status of the operational parameter, by the host computing device, a first timestamp indicative of when the image forming apparatus started to execute the printing operation, and a second timestamp indicative of when the image forming apparatus completed the printing operation. The method still further includes evaluating a performance level of the image forming apparatus by comparing an elapsed time between the first timestamp and second timestamp to an expected operation execution time. 
     In a second aspect, a system is provided. The system includes an image forming apparatus configured to execute an operation in response to receiving instructions to execute the operation. The system further includes an external sensor circuit comprising one or more sensors and a processor. The one or more sensors are configured to detect a status of an operational parameter of the image forming apparatus indicative of the image forming apparatus executing the operation, and the processor is configured to send notifications of the status of the operational parameter. The system yet further includes a host computing device, wherein the host computing device is configured to generate, in response to receiving the notifications of the status of the operational parameter, a first timestamp indicative of when the image forming apparatus started to execute the printing operation, and a second timestamp indicative of when the image forming apparatus completed the printing operation. The host computing device is further configured to generate a log file. Data of the log file includes the first timestamp and the second timestamp, and is indicative of how quickly the image forming apparatus executed the operation. 
     In a third aspect, a non-transitory computer-readable medium having instructions stored thereon is included. Upon execution by at least one processor, the instructions cause an image forming operation monitoring system to perform steps. The steps include receiving, by an image forming apparatus, instructions to execute an operation of the image forming apparatus. The steps further include, in response to receiving the instructions, executing, by the image forming apparatus, the operation. The steps yet further include detecting, by an external sensor circuit, a status of an operational parameter of the image forming apparatus indicative of the image forming apparatus executing the operation. The steps additionally include sending, by the external sensor circuit, notifications of the status of the operational parameter to a host computing device. The steps also include generating, in response to receiving the notifications of the status of the operational parameter, by the host computing device, a first timestamp indicative of when the image forming apparatus started to execute the printing operation, and a second timestamp indicative of when the image forming apparatus completed the printing operation. The steps still further include evaluating a performance level of the image forming apparatus by comparing an elapsed time between the first timestamp and second timestamp to an expected operation execution time. 
     In a fourth aspect, a system is provided that includes means for monitoring an image forming operation. The system includes means for receiving instructions to execute an operation of the image forming apparatus. The method further includes means for, in response to receiving the instructions, executing the operation. The method yet further includes means for detecting a status of an operational parameter of the image forming apparatus indicative of the image forming apparatus executing the operation. The method additionally includes means for sending notifications of the status of the operational parameter to a host computing device. The method also includes means for generating, in response to receiving the notifications of the status of the operational parameter, a first timestamp indicative of when the image forming apparatus started to execute the printing operation, and a second timestamp indicative of when the image forming apparatus completed the printing operation. The method still further includes means for evaluating a performance level of the image forming apparatus by comparing an elapsed time between the first timestamp and second timestamp to an expected operation execution time. 
     Other aspects, embodiments, and implementations will become apparent to those of ordinary skill in the art by reading the following detailed description, with reference where appropriate to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a schematic block diagram illustrating an image forming operation monitoring system, according to an example embodiment. 
         FIG. 2  is a schematic block diagram illustrating an image forming operation monitoring system, according to another example embodiment. 
         FIG. 3  is a schematic block diagram illustrating an image forming operation monitoring system, according to another example embodiment. 
         FIG. 4  is a simplified illustration of an image forming operation monitoring system, according to an example embodiment. 
         FIG. 5  is a simplified illustration of an external sensor of an image forming operation monitoring system, according to an example embodiment. 
         FIG. 6  is a simplified illustration of an input and output of an external sensor circuit of an image forming operation monitoring system, according to an example embodiment. 
         FIG. 7  is a simplified illustration of another sensor of an image forming operation monitoring system, according to an example embodiment. 
         FIG. 8  is a flow chart illustrating an example method of monitoring an image forming operation. 
         FIG. 9  is a flow chart illustrating another example method of monitoring an image forming operation. 
         FIG. 10  is a flow chart illustrating another example method of monitoring an image forming operation. 
         FIG. 11  is a block diagram illustrating a method of monitoring an image forming operation. 
         FIG. 12  is a flow chart illustrating another example method of monitoring an image forming operation. 
         FIG. 13  is a flow chart illustrating another example method of monitoring an image forming operation. 
         FIG. 14  is a block diagram illustrating a method of monitoring an image forming operation. 
         FIG. 15  is a block diagram illustrating a method of monitoring an image forming operation. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, reference is made to the accompanying figures, which form a part hereof. In the figures, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, figures, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the scope of the subject matter presented herein. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, separated, and designed in a wide variety of different configurations, all of which are explicitly contemplated herein. 
     I. Overview 
     Image forming apparatuses may perform a plurality of operations, such as printing, copying, scanning, or faxing operations. In performing each such operation, an image forming apparatus may receive instructions to perform the operation, and, in response, may perform the operation. 
     Various factors, such as network connectivity, received operation data, ink usage, or other factors may affect the time it takes the image forming apparatus to perform the operation. For example, poor network connectivity may negatively affect the time it takes the image forming apparatus to receive printing data, and thus cause the image forming apparatus to perform a printing operation slowly. As another example, the image forming apparatus may receive a large amount of printing, copying, scanning, or fax data, causing the image forming apparatus to perform the operation slowly. As yet another example, the image forming apparatus may receive printing or copying data that requires the image forming apparatus to use a large quantity of ink, causing the image forming apparatus to perform the operation slowly. 
     To determine whether the image forming apparatus is performing an operation satisfactorily, an image forming apparatus provider, or an image forming apparatus user, may monitor the image forming apparatus to determine how quickly the image forming apparatus performs the operation. The image forming apparatus provider or user may compare the time the image forming apparatus takes to perform the apparatus to an expected performance time. For example, an image forming apparatus provider may test the performance of an image forming apparatus by sending a plurality of print jobs to the image forming apparatus, and may use a stop watch to determine how quickly the image forming apparatus prints the print jobs. In another example, an image forming apparatus user may rely on anecdotal evidence of the performance times of the image forming apparatus. Determining the performance level of an image forming apparatus in such a manual or arbitrary fashion may waste time and money, and may inaccurately or inconsistently represent how quickly the image forming apparatus performs various tasks. 
     Systems and methods are disclosed herein that provide efficient, accurate, and consistent means of monitoring an image forming apparatus to determine operation performance times of image forming apparatuses. It should be understood that instructions to perform image forming operations such as printing, copying, scanning, or faxing operations may be divided into any number of pages, frames, slides, sections, words, or images. As such, an expected performance time of the image forming operation may be contextual, and different types of image forming operations may be measured or evaluated differently. Further, though printing, copying, scanning, and faxing operations are discussed herein, other types of image forming operations may be measured and evaluated using the systems and methods described. 
     In an example scenario, an image forming apparatus provider may evaluate the performance of printing operations of an image forming apparatus that has received a software update. Evaluating the performance times may allow the image forming apparatus provider to determine whether the software update has resulted in shorter printing times, or whether new errors arise as a result of the software update. In other words, one potential use of the systems and methods described herein is to troubleshoot software updates on an image forming apparatus. It should be understood that, in other examples, the systems and methods described may be used for other purposes. 
     To evaluate the printing operations, the image forming apparatus provider may send printing operation instructions to the image forming apparatus. For example, a host computing device may send the instructions to the image forming apparatus. The instructions may be substantially identical to instructions sent to the image forming apparatus prior to installation of the software update. Further, the provider may possess a record of the performance of the printing operation instructions by the image forming apparatus prior to the software update. Such a record may be stored on the host computing device. The record may take the form of, for example, a log file generated by the host computing device as the image forming apparatus performed the printing operation. 
     In response to receiving the instructions, the image forming apparatus may perform the operation. For purposes of the present example, the software update may result in a slightly slower (i.e. worse) performance time than that recorded prior to the software update. 
     One or more sensors external to the image forming apparatus may be used to determine an operational status of the image forming apparatus as it performs the operation. For example, a light sensor may determine that a light on the image forming apparatus has started to blink, indicating that the image forming apparatus is performing the operation. A printed page sensor may detect pages leaving the image forming apparatus, indicating the same. The sensors may further determine when the printer has finished performing the operation. The external sensors may send data indicative of the operational status to the host computing device, perhaps via one or more processors associated with the external sensors. 
     The host computing device may generate another log file based on this received data from the external sensors. It may then evaluate the image forming apparatus based on a comparison of the log file generated prior to installing the software update, and that generated post-update. 
     Since the systems and methods described herein may be more accurate and consistent than manual methods of evaluating printer performance, they may catch the slightly slower performance time where such manual methods may not. Further, such systems and methods may streamline and reduce costs of such troubleshooting an image forming apparatus. Other uses of the present disclosure will be readily apparent to those having skill in the art. 
     The present example should not be construed as limiting. The systems and methods described below may allow for evaluation of different image forming operations, using different combinations of external sensors, using more or fewer steps, or may be performed in different contexts than those presented in the example scenario. Such additional uses and applications of these systems and methods will be apparent to those having ordinary skill in the art. 
     II. System Examples 
       FIG. 1  is a schematic block diagram illustrating an image forming operation monitoring system  100  according to an example embodiment. The system includes a host computing device  102 , an image forming apparatus  104 , and an external sensor circuit  106 . The host computing device  100  may be communicatively coupled to the image forming apparatus  104 . For example, these devices may be directly coupled via a universal system bus (USB) connection. In other examples, they may be wirelessly coupled via a wireless access point. Other direct or wireless communicative coupling is possible as well, and will be readily ascertained by those having ordinary skill in the art. Further, though host computing device  100  and image forming apparatus  104  are depicted in  FIG. 1  as being communicatively coupled, it should be understood that the disclosed systems and methods do not require such communicative coupling to monitor or evaluate performance of an image forming apparatus. 
     The host computing device  102  may send instructions to the image forming apparatus  104  The image forming apparatus  104  may perform an operation or operations in response to receiving the instructions. Further, the image forming apparatus  104  may send updates to the host computing device  102  indicative of a status of the image forming apparatus  104 . For example, the image forming apparatus  104  may send a notification to the host computing device  100  indicating that the image forming apparatus  104  received instructions to perform the operation or operations. Other notifications or exchanges of data from the image forming apparatus to the host computing device  102  are possible as well. 
     The external sensor circuit  106  may be configured to detect an operational status of the image forming apparatus  104 . For example, the external sensor unit  104  may include sensors that detect a blinking light of the image forming apparatus  104 . The blinking light may indicate that the image forming apparatus is performing an image forming operation. 
     The external sensor circuit  106 , in turn, may be configured to send data indicative of the detected operational status of the image forming apparatus  104  to the host computing device  102 . The host computing device, based on this data, and perhaps further based on updates received from image forming apparatus  104 , may evaluate the performance of the image forming apparatus. 
       FIG. 2  is a schematic block diagram illustrating an image forming operation monitoring system  200 , according to another example embodiment. In this example embodiment, the host computing device  102  may include a processor  202  and a computer readable medium  204 . The processor  202  may include for example, a microprocessor. The computer-readable medium  204  may include, for example, random access memory, flash memory, and/or secure digital memory. Other types of processors and memories are possible as well. The computer readable medium  204 , such as a non-transitory computer readable medium, may have instructions stored thereon that are executable by the processor  202  to perform steps. For example, processor  202  may execute the instructions to send the instructions, receive the updates, and/or receive the sensor data described above with regard to  FIG. 1 . 
     Image forming apparatus  104 , may include operational indicators  206  that indicate that the image forming apparatus is performing an image forming operation, or indicate a status of performance of the operation. For example, the operational indicators  206  may include one or more indicator lights, such as a “busy” light emitting diode (LED) indicative of performance of the operation or an “attention” LED indicative, in some contexts, of an error occurring during performance of the operation. The operational indicators  206  may also include one or more printed page outputs on the image forming apparatus  104 . 
     External sensor circuit  106  may also include a processor  212  that may execute instructions on a computer readable medium  214  to perform steps. For example, processor  212  may execute the instructions to detect the operational status of the image forming apparatus  104  or to send the data indicative of the detected operational status of the image forming apparatus  104  to the host computing device  102  as described above with regard to  FIG. 1 . 
     External sensor circuit  106  may further include one or more light sensors  208  within a single unitary device. The light sensors may be configured to detect a status of operational indicators  206 , such as indicator lights of the image forming apparatus  104 . 
     The system may further include one or more paper sensors  208 . The one or more paper sensors  208  may be configured to detect a status of operational indicators  206 , such as printed page outputs of the image forming apparatus  104 . In the present example, the one or more paper sensors  208  may interface with the external sensor circuit  106  via processor  212 . Throughout the detailed description, it should be understood that the external sensor circuit  106  may include one or more sensors external to the image forming apparatus  104  within a single unitary device, and may interface with one or more sensors external to both the external sensor circuit  106  and the image forming apparatus  104 . 
       FIG. 3  is a schematic block diagram illustrating an image forming operation monitoring system  300 , according to another example embodiment. In the present example, the host computing device and the external sensor circuit are included within a single unitary device. In this way, the host computing device/external sensor circuit  302  may perform the functions associated with both the host computing device  102  and external sensor circuit  106  as described above with regard to  FIGS. 1 and 2 . For example, processor  304  may execute instructions stored on computer readable medium  306  to send instructions to, and receive updates from, image forming apparatus  104 , and detect a status of operational indicators  206 , as described above with regard to  FIGS. 1 and 2 . 
     The system may further include one or more sensors  308  external to both the host computing device/external unit  302  and the image forming apparatus  104 . Though in the present example each such sensor is illustrated as being included externally to the host computing device/external sensor circuit  302 , it should be understood that, in alternative embodiments, the one or more sensors may be included within the host computing device/external sensor circuit  302 . In still other embodiments, some of the one or more sensors may be included within host computing device/external sensor circuit  302 , and others may be included externally to host computing device/external sensor circuit  302 . 
       FIG. 4  is a simplified illustration of an image forming operation monitoring system  400 , according to an example embodiment. The present example system includes host computing device  402 , image forming apparatus  404 , external sensor circuit  416 , paper sensor  414  and light sensor  410 . 
     As described above with regard to  FIGS. 1, 2, and 3 , the host computing device  402  may be communicatively coupled to the image forming apparatus  404 , and may send instructions to perform an image forming operation to the image forming apparatus  404 . In response, the image forming apparatus  404  may perform the operation. 
     In the present example, the image forming apparatus  404  includes monitor  406  that includes an indicator light  408 , a printed page output  412 , and a scanned/faxed page output  418 . Each of these components of the image forming apparatus  404  may serve as an operational indicator of the image forming apparatus  404 . In other embodiments, the image forming apparatus  404  may include additional or fewer components. For example the image forming apparatus  404  may simply include a printed page tray or a scanned page tray, or may include additional indicator lights. 
     Because various image forming apparatuses may include different operational indicators, the sensors used in the example embodiments described herein may be modular. For example, the system illustrated by  FIG. 4  may readily accept an additional page sensor configured to detect scanned or faxed pages output at scanned/faxed page output  418 . Such additional sensors may be able to interface with external sensor circuit  416 . 
     Further, though page sensor  414  is used to detect printed pages at printed page output  412 , the page sensor may be used differently in different contexts. For example, if placed at scanned/faxed page output  418 , page sensor  414  may provide data that is interpreted differently by the external sensor circuit  416  and host computing device  402 . For example, an expected performance time may be shorter for a scanning or faxing operation associated with scanned/faxed page output  418  than for printed page output  412 . 
     In some embodiments, external sensor circuit  416  may simply include a means for interfacing with sensors  414  and  410  and means for communicating data received from the external sensors to host computing device  402 . In other embodiments, external sensor circuit  416  may perform some processing of data received from sensors  414  and  410  prior to sending corresponding data to host computing device  402 . Further, in some examples, external sensor circuit  416  may be a cellular phone or tablet device capable of interfacing with the sensors via hardware components on the device based on a software application stored thereon. In other examples, external sensor circuit  416  may be a standalone device such as that depicted in  FIG. 4 . In such examples, external sensor circuit  416  may include interactive features that allow a user to set, for example, which sensors are used, or specify a make and model of the image forming apparatus  404  to be monitored by the external sensor circuit  416 . The external sensor circuit  416  may include a display that, among other information, displays a detected operational status of the image forming apparatus  404  based on data received from sensors  410  and  414 . Other interactive features and display features are possible as well. 
       FIG. 5  is a simplified illustration of an external sensor of an image forming operation monitoring system  500 , according to an example embodiment. In  FIG. 4 , light sensor  410  is depicted as a light-sensitive diode. The light-sensitive diode may be included within a light-sensitive transducer  502 , which, for purposes of simplicity, shall be referred to as a light sensor. Light sensor  502  may alternatively or additionally include a photoresistor. Other light-sensitive components are possible as well. 
     Light sensor  502  may be additionally configured to interface with the external sensor circuits described about with regard to  FIGS. 1 through 4 , perhaps via one or more processors disposed within the light sensor  502  and a corresponding sensor circuit. For example, light sensor  502  may be communicatively coupled to an external sensor circuit directly, or wirelessly. The present example includes a communication terminal  504  and a transceiver  506 . Such wireless communication may be achieved via a wireless access point, BLUETOOTH® communication, or ZIGBEE® interface. Other wireless communication schemes are possible as well. Thus, light sensor  502  may detect light output by indicator light  408 , perform preliminary processing on the detected light by a processor included within sensor  502 , and communicate data representative of the detected light to an external sensor circuit via communication terminal  504  and transceiver  506 . 
       FIG. 6  is a simplified illustration of an input and output of an external sensor circuit of an image forming operation monitoring system  600 , according to an example embodiment. Light sensor  502  described above may initially detect waveform  602 . The waveform may result from a rapidly blinking indicator light, such as indicator light  408 . The indicator light may blink imperceptibly to the human eye, and may blink several times during an “On” status of the light. As such, a processor associated with the light sensor  502  may determine an On/Off waveform  604  for transmission to an external sensor circuit. It should be understood that, while each sensor of the systems and methods descried herein may perform such processing prior to sending data to an external sensor circuit or host computing device, such processing may alternatively be performed by an external sensor circuit or host computing device. 
       FIG. 7  is a simplified illustration of another sensor of an image forming operation monitoring system  700 , according to an example embodiment. In the present example, printed page sensor  414 , as depicted in  FIG. 4 , may include a light source  414 A, a mechanical light blocker  414 B, and a light sensor  414 C. As printed page  702  is output to printed page output  412 , the mechanical light blocker  414 B is moved, thereby allowing the light from light source  414 A to pass to light sensor  414 C. In other embodiments, such a printed page sensor may be implemented using a mechanical switch. Other example printed page sensors are possible as well. Further, as noted above, such a sensor may be used in different contexts and may be used as a modular component that is flexibly added to, or removed from, an image forming operation monitoring system. 
     III. Example Methods 
       FIG. 8  is a flow chart  800  illustrating an example method of monitoring an image forming operation. In the present example, the method is carried out by host computing device  802 , image forming apparatus  804 , and an external sensor circuit that includes one or more sensors  806  and a processor  808 . 
     In the present example, at block  810 , the host computing device  802  generates print data at block  810  and sends a print job to the image forming apparatus  804 . At block  814 , the host computing device  802  further generates a timestamp indicative of the time at which the host computing device  802  started to send the print job to the image forming apparatus  804 . Once the host computing device has finished sending the print job, at block  818 , the host computing device generates a timestamp indicative of having finished sending the print job. In some embodiments, such timestamps may be used to determine how effective the communication is between the host computing device  802  and the image forming apparatus  804 . For example, the time elapsed between the timestamp indicative of starting to send the print job and the timestamp indicative of having sent the print job may be compared to an expected print job sending time. 
     At block  820 , the image forming apparatus  804  starts to print responsive to receiving the print job. In the present example, an LED blinks to indicate that the printing operation has started. At block  822 , the one or more sensors  806  detect the blinking LED, and notify the processor  808  of the external sensor circuit that the LED has started to blink. The processor  808 , in turn, notifies the host computing device  802  of the same. 
     At block  828 , responsive to being notified that the LED has started blinking, the host computing device  802  generates a timestamp indicative of the LED starting to blink, and, accordingly, indicative of the image forming apparatus  804  starting to perform the printing operation. 
     At block  830 , the image forming apparatus  804  finishes the print job. Accordingly, the LED stops blinking. At block  832 , the one or more sensors  806  detect that the blinking LED has stopped, and notify the processor  808  of the external sensor circuit that the LED has stopped blinking. The processor  808 , in turn, notifies the host computing device  802  of the same. 
     At block  838 , responsive to being notified that the LED has stopped blinking, the host computing device generates a timestamp indicative of the LED ceasing to blink, and, accordingly, indicative of the image forming apparatus  804  having completed the printing operation. 
     At block  840 , host computing device generates a log file. The log file may include each of the timestamps generated during the printing operation process. The host computing device  802  may additionally compare the generated log file to past logs files, or exemplary log files that contain different timestamps indicative of an expected printing operation completion time. The host computing device  802  may compare these timestamps to evaluate performance of the printing operation. 
     As noted above, the timestamps associated with blocks  810  and  814  may be used to determine a performance level associated with sending the print job from the host computing device  802  to the image forming apparatus  804 . However, in other embodiments, the timestamps associated with blocks  828  and  838  may be used to evaluate performance of the printing operation, since such data may more accurately represent how the image forming apparatus  804  executes instructions once they are received. In still other embodiments, each timestamp may be used to evaluate an overall performance level of the image forming apparatus  804 . 
     The flow chart depicted in  FIG. 8  could be performed iteratively to determine a more comprehensive evaluation of the image forming apparatus  804 . For example, the host computing device  802  could successively generate print data and send a plurality of print jobs to the image forming apparatus. Such print jobs may vary in page number, or ink usage. As such, instructions from host computing device  802  to execute the operation of the image forming apparatus  804  may include a plurality of print jobs to be executed by the image forming apparatus in succession. 
     Evaluating performance of an image forming operation may simply include determining whether the image forming operation was performed within an expected operation execution time. However, in other examples, the total time between starting to send the image forming operation instructions and completion of the image forming operation may be used. In still other examples, a total time to perform a series of image forming operations may be used. 
     The host computing device may perform an action responsive to evaluating performance of the image forming operation. For example, responsive to determining that the image forming apparatus has not performed an image forming operation within an expected operation execution time, the host computing device may flag the image forming apparatus for maintenance. In other examples, the host computing device may cause the image forming apparatus to revert to an earlier firmware or software installation. In still other examples, the host computing device may send instructions to perform particular image forming operations to the image forming apparatus. For instance, upon determining that the image forming apparatus has not performed a printing operation within an expected printing operation execution time, the host computing device may send instructions to perform the same printing operation. Other examples of actions taken in response to determining that the image forming apparatus has not performed an image forming operation within an expected operation execution time are possible as well. 
       FIG. 9  is a flow chart  900  illustrating another example method of monitoring an image forming operation. In the present example, the method is carried out by host computing device  902 , image forming apparatus  904 , and an external sensor circuit that includes one or more sensors  906  and a processor  908 . However, in the present example, the image forming operation being monitored is a copying operation. As such, the method and system components operate differently in the present example than in that describe above with regard to  FIG. 8 . 
     For example, at block  910 , the image forming apparatus  904  receives instructions to perform the copying operation. These instructions are not necessarily sent by host computing device  902 . Rather, the instructions may be input via user interface  406  as depicted in  FIGS. 4 and 5 . Indeed, it should be understood that, regardless of the image forming operation type, such instructions may be received from any number of sources other than the host computing device  902 . For example, the instructions may be received from a portable memory device, such as a flash drive, or from any client device within a network environment shared by the image forming apparatus  904 . 
     In the present example, after receiving the instructions to perform the copying operation, the system may monitor and evaluate performance of the copying operation in much the same way described above with regard to  FIG. 8 . However, it should be understood that different combinations of sensors may be used to detect performance of the copying operation than those used to detect performance of the printing operation described above. In some examples, the same combination of sensors may be used for both printing operations and copying operations. Further, the timestamps associated with blocks  914 ,  924 , and  934  may be evaluated differently than those associated with blocks  810 ,  814 ,  828 , and  838  of  FIG. 8 . For example, an expected copying operation completion time may be different than an expected printing operation completion time; even if the information received for a printing operation is substantially similar to the information received for the copying operation. 
       FIG. 10  is a flow chart  1000  illustrating another example method of monitoring an image forming operation. In the present example, the method is carried out by host computing device/external sensor circuit  1002 , which includes one or more processors  1004  and sensors  1006 , and image forming apparatus  1008 . The method illustrated in the present example is substantially the same as that illustrated above with regard to  FIG. 8 , except that the various steps of sending data from the external sensor circuit to host computing device  802  are no longer necessary. 
     It should be understood that  FIGS. 8, 9, and 10  are provided for illustrative purposes only and should not be construed as limiting. Though only methods of monitoring printing operations and copying operations have been described, scanning, faxing, or other image forming operations may be monitored using similar steps and system component configurations. 
     In some examples, while performing an image forming operation in response to receiving instructions from a host computing device, an image forming apparatus may perform other operations having a higher priority than the original image forming operation. In particular, such intervening operations may be carried out while an external sensor device is monitoring performance of the image forming apparatus. In such examples, the external sensor device may detect the intervening operation, and notify the host computing device of the intervening operation, thereby causing an interrupt in timestamps used to record performance of the image forming apparatus. 
       FIG. 11  is a block diagram  1100  illustrating a method of monitoring an image forming operation. In some examples, the method may be carried out as part of a system. For example, block  1102  may be carried out by an image forming apparatus in conjunction with one or more processors associated with the image forming apparatus. 
     In other examples, the method may be carried out as part of a computing system. In these examples, a non-transitory computer readable medium may store instructions executable by one or more processors associated with the computing system to cause the computing system to perform the blocks of the method. 
     Block  1102  of the method may be performed to receive, by an image forming apparatus, instructions to execute an operation of the image forming apparatus. For example, as depicted in  FIG. 8 , the image forming apparatus may receive instructions to perform a print job. 
     Block  1104  of the method may be performed to, in response to receiving the instructions, execute, by the image forming apparatus, the operation. For example, as depicted in  FIG. 8 , the image forming apparatus may start printing responsive to receiving the print job. 
     Block  1106  of the method may be performed to detect, by an external sensor circuit, a status of an operational parameter of the image forming apparatus indicative of the image forming apparatus executing the operation. For example, as depicted in  FIG. 8 , in response to receiving the print job, an LED of the image forming apparatus may start to blink to indicate that the image forming apparatus is performing the printing operation. Further, as depicted, an external sensor circuit may detect an On/Off status of the LED blinking. 
     Block  1108  of the method may be performed to send, by the external sensor circuit, notifications of the status of the operational parameter to a host computing device. For example, as depicted in  FIG. 8 , responsive to detecting the On/Off status of the LED blinking and ceasing to blink, the external sensor circuit may send notifications to a host computing device that the image forming apparatus has started to perform the printing operation, and completed performing the printing operation. 
     Block  1110  of the method may be performed to generate, in response to receiving the notifications of the status of the operational parameter, by the host computing device, a first timestamp indicative of when the image forming apparatus started to perform the printing operation, and a second timestamp indicative of when the image forming apparatus completed the printing operation. For example, as depicted in block  828  of  FIG. 8 , the host computing device may generate a timestamp indicative of a time when the LED started to blink, and, accordingly, when the image forming apparatus started to perform the printing operation. Further, as depicted in block  838  of  FIG. 8 , the host computing device may generate a timestamp indicative of a time when the LED stopped blinking, and, accordingly, when the image forming apparatus completed the printing operation. 
     Though the method depicted by  FIG. 11  has been described by the exemplary flow chart depicted in  FIG. 8 , it should be understood that the steps of  FIG. 11  are equally representative of the flow charts depicted in  FIGS. 9 and 10 . Further, the steps of  FIG. 11  may be carried out by any combination of system components described throughout the detailed description. 
     IV. Additional Embodiments 
       FIG. 12  is a flow chart  1200  illustrating another example method of monitoring an image forming operation. In the present example, the method is carried out by host computing device  1202 , image forming apparatus  1204 , and an external sensor circuit that includes one or more sensors  1206  and a processor  1208 . 
     In the present example, at block  1210 , the host computing device  1202  generates print data and, at block  1212 , starts sending a print job to the image forming apparatus  1204 . At block  1214 , the host computing device  1202  further generates a timestamp indicative of the time at which the host computing device  1202  started to send the print job to the image forming apparatus  1204 . Though not depicted in  FIG. 12 , it should be understood that once the host computing device has finished sending the print job, the host computing device generates a timestamp indicative of having finished sending the print job. 
     At block  1216 , the image forming apparatus  1204  starts to print responsive to receiving the print job. In the present example, an LED blinks to indicate that the printing operation has started. At block  1218 , the one or more sensors  1206  detect the blinking LED, and notify the processor  1208  (notification signal  1220 ) of the external sensor circuit that the LED has started to blink. The processor  1208 , in turn, notifies the host computing device  1202  of the same (notification signal  1222 ). 
     At block  1224 , responsive to being notified that the LED has started blinking, the host computing device  1202  generates a timestamp indicative of the LED starting to blink, and, accordingly, indicative of the image forming apparatus  1204  starting to perform the printing operation. 
     At block  1226 , image forming apparatus  1204  performs an intervening operation. For instance, image forming apparatus  1204  may receive an instruction (e.g. from another computing device) to perform an intervening operation having a higher priority than the original printing operation, such as a fax job or a scan job. In other examples, the intervening operation may be part of a pre-existing routine of image forming apparatus  1204 . For instance, image forming apparatus  1204  may periodically perform necessary tasks such as software updates, color calibration, color registration, and/or head cleaning. These operations may also be performed automatically in response to image forming apparatus  1204  detecting a threshold level of use, such as after detecting a threshold number of pages being printed. Some or all of these operations may be initiated manually as well. 
     In further examples, the intervening operation may include start-up or follow-up procedures of the image forming apparatus  1204 . For instance, image forming apparatus  1204  may perform warm up prior to performing certain operations. Image forming apparatus  1204  may warm up when booting up or recovering from a power-saving mode, or after an image forming operation has been paused for a threshold period of time. Thus, a warm up procedure may indicate that image forming apparatus  1204  is about to perform, or continue performing, printing, copying, faxing or other image forming procedures. 
     At block  1228 , the one or more sensors  1206  detect the intervening operation using one or more operational parameters exhibited by image forming apparatus  1204  during runtime. One such operational parameter may include sounds exhibited by image forming apparatus  1204 . For instance, the one or more sensors  1206  may include a microphone configured to detect sounds emanating from image forming apparatus  1204 , and determine an operation, such as a warm up operation of image forming apparatus  1204 , based on the detected sounds. Such operations may be performed, for example, in much the same way described in U.S. Pat. No. 9,712,686, issued Jul. 18, 2017, which is hereby incorporated by reference in its entirety. In particular, an external sensor circuit that includes the one or more sensors  1206  may receive an audio signal by way of a microphone. In turn, a processor, such as processor  1208 , may execute program instructions to compare the audio signal with predetermined representations of particular intervening operations to identify which intervening operation is being performed by image forming apparatus  1204 . 
     In other examples, an external sensor unit may rely on operational parameters exhibited by a user interface of image forming apparatus  1204 , such as user interface  406  depicted in  FIGS. 4 and 5 , to detect an intervening operation. In these examples, the one or more sensors  1206  may include a camera configured to detect images that correspond to a user interface of image forming apparatus  1204 . Detecting an intervening operation may include analyzing an image that represents the user interface to identify icons or phrases indicative of a particular intervening operation. For example, an external sensor circuit may receive an image from the camera, and a processor, such as processor  1208 , may execute program instructions to recognize language or icons displayed on the user interface of image forming apparatus  1204 . The recognized language or icons may be compared to predetermined representations of particular intervening operations to identify which intervening operation is being performed by image forming apparatus  1204 . Additionally or alternatively, an external sensor circuit may receive indications of the operations directly from image forming apparatus  1204 . For instance, image forming apparatus  1204  may include operational identifiers that are accessible over a network or wired connection during runtime, and the external sensor circuit may interface with image forming apparatus  1204  to determine which intervening operation is being performed. 
     In still other examples, the external sensor circuit may utilize sensors already included within image forming apparatus  1204  to detect intervening operations. For example, the external sensor unit may interface with existing sensors to monitor color calibration, rolling drums, paper paths, or other components within image forming apparatus  1204 . 
     After detecting an intervening operation at block  1228 , one or more sensors  1206  may send a notification signal  1230  to processor  1208 , which in turn may send a notification signal  1232  to host computing device  1202 . 
     At block  1234 , responsive to receiving a notification from the external sensor circuit, host computing device  1202  may generate an interrupt timestamp to signify that the external sensor circuit will resume monitoring performance of image forming apparatus  1204  after the intervening operation has completed. Host computing device  1202  may further generate a log file containing representations of these timestamps, and use the log file as a basis for evaluating performance of image forming apparatus  1204  in later evaluations. 
     Though not depicted in  FIG. 12 , the external sensor circuit may determine that the intervening operation has ended and that the originally-monitored operation of image forming apparatus  1204  has recommenced. In response to such a determination, the external sensor circuit sends an indication to host computing device  1202 , which, in turn, creates a timestamp indicating that the interrupt in monitoring has ended. An elapsed time between the start of interrupt timestamp and end of interrupt timestamp (an interrupt timestamp pair) signifies an operation that the external sensor circuit was not intended to monitor, so this elapsed time may be omitted from an evaluation of performance of image forming apparatus  1204 . 
     It should be understood that, though only a single intervening operation is described with respect to  FIG. 12 , two or more intervening operations may occur prior to completion of the monitored operation. In such examples, the external sensor circuit may notify host computing device  1202  of each instance of an intervening operation beginning and ending, host computing device  1202  may generate corresponding interrupt timestamp pairs, and elapsed time between each interrupt timestamp pair may be omitted from an evaluation of performance of image forming apparatus  1204 . 
       FIG. 13  is a flow chart  1300  illustrating another example method of monitoring an image forming operation. In the present example, the method is carried out by host computing device  1302 , image forming apparatus  1304 , and an external sensor circuit that includes one or more sensors  1306  and a processor  1308 . 
     In the present example, at block  1310 , the host computing device  1302  generates print data and, at block  1310 , starts sending a print job to the image forming apparatus  1304 . At block  1314 , the host computing device  1302  further generates a timestamp indicative of the time at which the host computing device  1302  started to send the print job to the image forming apparatus  1304 . 
     At block  1316 , the image forming apparatus  1304  starts to print responsive to receiving the print job. In the present example, an LED blinks to indicate that the printing operation has started. At block  1318 , the one or more sensors  1306  detect the blinking LED, and notify the processor  1308  (notification signal  1320 ) of the external sensor circuit that the LED has started to blink. The processor  1308 , in turn, notifies the host computing device  1302  of the same (notification signal  1322 ). 
     At block  1324 , responsive to being notified that the LED has started blinking, the host computing device  1302  generates a timestamp indicative of the LED starting to blink, and, accordingly, indicative of the image forming apparatus  1304  starting to perform the printing operation. 
     At block  1326 , the external sensor circuit, and processor  1308  in particular, receives an instruction. The instruction may relate to excluding a portion of data used to detect an operational parameter of image forming apparatus  1304 . For instance, the instruction may specify that the external sensor device should stop obtaining data for a period of time, should stop analyzing obtained data to detect operational parameters of image forming apparatus  1304 , or should stop using particular sensors of the one or more sensors  1306 . Other instructions relating to excluding data associated with the external sensor circuit are possible as well. 
     The instruction can be received by way of a user interface of the external sensor circuit. For example, a user may select an option provided in the user interface to pause monitoring of image forming apparatus  1304 . Additionally or alternatively, the user interface may provide an option to resume such monitoring, or delay monitoring for a set period of time. These options may allow a user to perform maintenance on image forming apparatus  1304  or to use image forming apparatus  1304  to perform other operations without interfering with an evaluation of performance of image forming apparatus  1304 . 
     In other examples, the received instruction may be part of a regular schedule associated with image forming apparatus  1304 . Though the instruction may simply be periodic (e.g., sending an instruction to monitor image forming apparatus  1304  once each week at a predetermined time), other types of scheduling can be used. For example, a schedule may relate to pending maintenance of image forming apparatus  1304  or preventing monitoring image forming apparatus  1304  at times when users are more likely to need image forming tasks performed. Scheduling might be based on usage milestones as well. For example, after 1000 pages are printed within a given period, the external sensor circuit may be prompted to begin monitoring image forming apparatus  1304 . In this fashion, the external sensor circuit can be operated remotely to evaluate performance of image forming apparatus  1304 . 
     Responsive to receiving the instruction, the external sensor circuit may send notification signal  1328  to host computing device  1302 . 
     At block  1330 , host computing device  1302  creates an interrupt timestamp to signify that the external sensor circuit is excluding data indicative of operational parameters of image forming apparatus  1304 . 
     Though not depicted in  FIG. 13 , it should be understood that once host computing device  1302  has finished sending the print job, host computing device  1302  generates a timestamp indicative of having finished sending the print job. Further, though not depicted in  FIG. 13 , the external sensor circuit may receive an additional instruction to resume obtaining data related to an operational parameter of image forming apparatus  1304 , or may receive additional instructions to exclude at least a portion of data used to detect the status of an operational parameter. In response to such instructions, the external sensor circuit sends an indication to host computing device  1302 , which, in turn, creates a timestamp indicating that the initial instruction has ended. An elapsed time between the interrupt timestamp and the new instruction to resume collecting data (an interrupt timestamp pair) signifies a period that the external sensor circuit was instructed not to monitor, so this elapsed time may be omitted from an evaluation of performance of image forming apparatus  1304 . 
     It should be further understood that, though  FIGS. 12 and 13  are depicted and described in a similar fashion to the corresponding disclosure of  FIG. 8 , similar operations of host computing device  1202 / 1302 , image forming apparatus  1204 / 1304 , and the external sensor circuit (including one or more sensors  1206 / 1306  and processor  1208 / 1308 ) can be performed under the orientations disclosed with respect to  FIGS. 9 and 10 . Further, the steps of  FIGS. 12 and 13  may be carried out by any combination of system components described throughout the detailed description. 
       FIG. 14  is a block diagram  1400  illustrating a method of monitoring an image forming operation. In some examples, the method may be carried out as part of a system. For example, block  1402  may be carried out by an image forming apparatus in conjunction with one or more processors associated with the image forming apparatus. 
     In other examples, the method may be carried out as part of a computing system. In these examples, a non-transitory computer readable medium may store instructions executable by one or more processors associated with the computing system to cause the computing system to perform the blocks of the method. 
     Block  1402  of the method may be performed to receive, by an image forming apparatus, instructions to execute an operation of the image forming apparatus. 
     Block  1404  of the method may be performed to execute, by the image forming apparatus in response to receiving the instructions, the operation. 
     Block  1406  of the method may be performed to detect, by an external sensor circuit, a status of a first operational parameter of the image forming apparatus indicative of the image forming apparatus executing the operation. 
     Block  1408  of the method may be performed to detect, by the external sensor circuit, a status of a second operational parameter of the image forming apparatus indicative of the image forming apparatus executing an intervening operation. 
     Block  1410  of the method may be performed to send, by the external sensor circuit, notifications of the status of the first operational parameter and the second operational parameter to a host computing device. 
     Block  1412  of the method may be performed to generate, in response to receiving the notifications of the status of the first and second operational parameters, by the host computing device, a plurality of timestamps indicative of when the image forming apparatus executed the operation and when the image forming apparatus executed the intervening operation. 
     Block  1414  of the method may be performed to determine, based on the plurality of timestamps, an execution time of the operation. For example, as described above with respect to  FIG. 12 , interrupt timestamp pairs may be considered to determine periods that do not account for an image forming operation that is being evaluated. 
     For example, the plurality of timestamps may include a first timestamp indicative of when the image forming apparatus started to execute the operation, a second timestamp indicative of when the image forming apparatus completed the operation, a third timestamp indicative of when the image forming apparatus started to execute the intervening operation, and a fourth timestamp indicative of when the image forming apparatus completed the intervening operation. In the present example, determining the execution time of the operation can include determining a first elapsed time between the first timestamp and the second timestamp, determining a second elapsed time between the third timestamp and the fourth timestamp, and subtracting the second elapsed time from the first elapsed time. 
     Block  1416  of the method may be performed to evaluate a performance level of the image forming apparatus by comparing the execution time of the operation to an expected operation execution time. 
     Though the method depicted by  FIG. 14  has been described by the exemplary flow chart depicted in  FIG. 12 , it should be understood that the steps of  FIG. 14  are equally representative of the flow charts depicted in  FIGS. 8, 9 and 10 . Further, the steps of  FIG. 14  may be carried out by any combination of system components described throughout the detailed description. 
       FIG. 15  is a block diagram  1500  illustrating a method of monitoring an image forming operation. In some examples, the method may be carried out as part of a system. For example, block  1502  may be carried out by an image forming apparatus in conjunction with one or more processors associated with the image forming apparatus. 
     In other examples, the method may be carried out as part of a computing system. In these examples, a non-transitory computer readable medium may store instructions executable by one or more processors associated with the computing system to cause the computing system to perform the blocks of the method. 
     Block  1502  of the method may be performed to receive, by an image forming apparatus, instructions to execute an operation of the image forming apparatus. 
     Block  1504  of the method may be performed to execute, by the image forming apparatus, in response to receiving the instructions, the operation. 
     Block  1506  of the method may be performed to detect, by an external sensor circuit, a status of an operational parameter of the image forming apparatus indicative of the image forming apparatus executing the operation. 
     Block  1508  of the method may be performed to receive, by the external sensor circuit, an instruction to exclude at least a portion of data used to detect the status of the operational parameter. For example, as described above with respect to  FIG. 13 , the instruction to exclude at least a portion of data may include a schedule of times at which the external sensor circuit is to obtain data indicative of the operational parameter. In other examples, receiving the instruction to exclude at least a portion of data may include receiving, by way of a user interface module of the external sensor circuit, an indication that an option to pause data acquisition has been selected. 
     Block  1510  of the method may be performed to send, in accordance with the received instruction, by the external sensor circuit, notifications of the status of the operational parameter to a host computing device. 
     Block  1512  of the method may be performed to generate, in response to receiving the notifications of the status of the operational parameter, by the host computing device, a plurality of timestamps indicative of when the image forming apparatus executed the operation and a time frame when the external sensor circuit excluded data. 
     Block  1514  of the method may be performed to determine, based on the plurality of timestamps, an execution time of the operation. For example, as described above with respect to  FIG. 12 , interrupt timestamp pairs may be considered to determine periods that do not account for an image forming operation that is being evaluated. 
     For example, the plurality of timestamps may include a first timestamp indicative of when the image forming apparatus started to execute the operation, a second timestamp indicative of when the image forming apparatus completed the operation, a third timestamp indicative of when the image forming apparatus started to execute the intervening operation, and a fourth timestamp indicative of when the image forming apparatus completed the intervening operation. In the present example, determining the execution time of the operation can include determining a first elapsed time between the first timestamp and the second timestamp, determining a second elapsed time between the third timestamp and the fourth timestamp, and subtracting the second elapsed time from the first elapsed time. 
     Block  1516  of the method may be performed to evaluate a performance level of the image forming apparatus by comparing the execution time of the operation to an expected operation execution time. 
     Though the method depicted by  FIG. 15  has been described by the exemplary flow chart depicted in  FIG. 13 , it should be understood that the steps of  FIG. 15  are equally representative of the flow charts depicted in  FIGS. 8, 9 and 10 . Further, the steps of  FIG. 15  may be carried out by any combination of system components described throughout the detailed description. 
     While various examples and embodiments have been disclosed, other examples and embodiments will be apparent to those skilled in the art. The various disclosed examples and embodiments are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.