Insulation resistance tester with environment compensation

Abstract

An insulation resistance tester includes a set of testing cables structured to be coupled to a device under test, a measurement port coupled to the set of testing cables, a resistance measurement unit structured to determine a resistance measurement of the device under test by sending a signal from the measurement port and receiving a return signal from the measurement port, an environmental port structured to receive an input from an environmental sensor, a temperature compensator structured to modify the resistance measurement based on the input received from the environmental sensor, and a display structured to show an indication of the modified resistance measurement. Methods are also described.

Description

INSULATION RESISTANCE TESTER WITH ENVIRONMENT COMPENSATIONFIELD OF THE INVENTION

[0001] This disclosure relates to test and measurement devices, and, more particularly, to a test and measurement device that senses ambient conditions of the testing environment and makes use of the sensed conditions to inform a user about measurements made by the measurement device.BACKGROUND

[0002] Technicians use Insulation Resistance Testing (IRT) devices to measure insulation resistance of various devices, such as electrical wires, cables, motors, and transformers, for example. The resistance measurement indicates the state of the insulation in the device. Insulation that is failing may be detected as a fault, which may be a degradation or break in the insulation causing the cable to lose its insulative properties at the location of the fault. In operation, IRTs apply either an AC or DC voltage to an insulative material of a cable under test and measure current flow back through an electrical conductor of the cable. The IRT determines resistance values of the insulation, in Ohms, based on the applied voltage and the measured current, and presents the information to the user.

[0003] Environmental conditions present when an insulation resistance measurement is being taken may affect the accuracy of the resistance measurement. For example, insulation resistance changes in linear relation to temperature, where temperatures higher than the baseline temperature cause lower measured resistance values, and temperatures lower than the baseline temperature cause higher measured resistance values. The baseline temperature is the temperature at which the reference resistance value was taken.

[0004] Relative humidity is also an environmental condition that may affect the accuracy of insulation resistance measurement, but the relationship between humidity and the insulation resistance measurement is not as well understood as the relationship between temperature and the measured resistance values. Some technicians recognize that high humidity and temperature affects insulation readings, but many do not. And environmental information available through the internet is typically limited to an average temperature and possibly humidity of an entire city, so even checking for ambient testing conditions may result in inaccurate results.

[0005] Although it is known that environmental conditions of the testing environment may affect the reliability of insulation resistance measurements, no conventional IRTs consider any environmental conditions when measuring insulation resistance.BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Fig. 1 is a block diagram of an insulation resistance tester including environmental sensing ports, measurement compensation, and a user warning system according to embodiments of the disclosure.

[0007] Fig. 2 is a block diagram of an insulation resistance testing system including the insulation resistance tester coupled to a mobile device according to embodiments of the disclosure.

[0008] Fig. 3 is a flowchart of example operations used to generate a propagation velocity database and for compensating temperature measurements based on data stored in the database, according to embodiments of the disclosure.

[0009] Figs. 4A and 4B are example display screens that may be shown on a device of the insulation resistance testing system of Fig. 2, according to embodiments.

[0010] Figs. 5A and 5B are example display screens with alerts that may be shown on a device of the insulation resistance testing system of Fig. 2, according to embodiments.

[0011] Fig. 6 is an example display screen illustrating an environmental condition warning that may be presented to a user of the insulation resistance testing system of Fig. 2, according to embodiments.

[0012] Fig. 7 is another example display screen illustrating an environmental condition warning that may be presented to a user of the insulation resistance testing system of Fig. 2, according to embodiments.DETAILED DESCRIPTION

[0013] Embodiments of the disclosure include an insulation resistance tester (IRT) having one or more environmental sensing ports, measurement compensation, and a user warning system. Since the disclosed IRT uses information about environmental conditions in which the IRT is operating, it is more accurate than conventional IRTs, and may prevent users from making errors in measurements or relying on potentially inaccurate data when environmental conditions prevent the IRT from making accurate measurements.

[0014] Fig. 1 is a block diagram of an insulation resistance tester 100 including environmental sensing ports, and other features, according to some embodiments of the disclosure. The insulation resistance tester 100 includes one or more measurement ports 102, which may be any electrical signaling medium. Measurement ports 102 may include receivers, transmitters, and / or transceivers. The insulation resistance tester 100 may couple to a Device Under Test, which may be referred to as a Cable Under Test (CUT) 130, through the one or more measurement ports 102. A pair of electrical test cables 132 connects the CUT 130 to the measurement ports 102. In the illustrated example, the CUT 130 is an electrical cable having a single conductor surrounded by an insulating material. Other types of devices that may be tested with the insulation resistance tester 100 include cables having one or more conductors surrounded by various combinations of insulators or insulation material. Some cables, such as coaxial cables, may include shielding as well. In this description, although the device being tested by the insulation resistance tester 100 is referred to as a CUT, which is for convenience, it is understood that the described insulation tester 100 could be used on any device where an insulation resistance measurement would be useful, and is not limited to only testing cables, but instead may be used to test type of devices where insulation resistance testing would be helpful.

[0015] The insulation resistance tester 100 includes one or more measurement units 140, which perform the main functions of measuring parameters and other qualities of signals from the CUT 130 being measured by the insulation resistance tester 100. Typical measurements include resistance, voltage, current, and power of input signals, as well as insulation-specific tests such as polarization index and dielectric absorption ratio. Some tests may be performed over time, using stepped voltages. The measurement units 140 represent any measurements that are typically performed on insulation resistance testers.

[0016] Embodiments according to the disclosure also include one or more environment sensing ports 104, which are coupled to the measurement units 140. As described in more detail below, the measurement units 140 may utilize information received through the environment sensing ports 104 when determining one or more measurements by the insulation resistance tester 100.

[0017] Several different environment sensors may be coupled to the one or more environment sensing ports 104 to provide sensed information about the environmental conditions in which the insulation resistance measurements are being made. For example,one type of sensor may be a temperature probe 150. In some embodiments, the temperature probe 150 may be coupled to the one or more environment sensing ports 104 through a cable 152. In other embodiments, the temperature probe 150 may be integrated into the insulation resistance tester 100 itself, such as being integrated within an instrument housing. In yet other embodiments, multiple temperature probes 150 may be coupled to the environment sensing ports 104, so as to measure various temperatures of the environment rather than just relying on a single sensor. In some embodiments a mean or median value of the multiple temperature probes 150 may be selected to be used by the measurement units 140. In yet other embodiments the user may select which of the several temperature probes 150 to use by the measurement units 140.

[0018] Another type of sensor coupled to the one or more environment sensing ports 104 is a humidity sensor 160. In Fig. 1, the humidity sensor 160 is coupled to the sensing ports 104 through a connection cable 162. The humidity sensor 160 operates to measure the relative humidity of the testing environment and communicate the sensed humidity information to the insulation resistance tester 100. Description of how the insulation resistance tester 100 uses information from the humidity sensor 160 is described in detail below.

[0019] Yet another type of sensor coupled to the one or more environment sensing ports 104 is an aimable temperature sensor 170, such as an InfraRed temperature sensor. In general, such aimable temperature sensors include a visible beam 172, created by a low- power laser, through which the user points the temperature sensor 170 to a particular spot to be measured. Then, the aimable temperature sensor 170 measures the temperature of whatever surface is illuminated by the visible beam 172. In embodiments according to the disclosure, the temperature sensor 170 may be aimed at the CUT 130 itself, or a particular spot on the surface of the CUT at which a temperature measurement is to be made. Then, after the temperature of the CUT 130 is measured, the temperature sensor 170 may communicate the temperature information back to the one or more environment sensing ports 104. In some embodiments both the one or more environment sensing ports 104 and the temperature sensor 170 include wireless ports, 105, 174 respectively, through which the measured temperature information may be wirelessly communicated from the temperature sensor to the insulation resistance tester 100. Of course, other communication methods are possible, including the user manually entering the temperature sensed by the temperature sensor 170.

[0020] Embodiments of the disclosure may include any or all of the sensors 150, 160, 170 described above, which inform the insulation resistance tester 100 about testing conditions when measuring insulation resistance.

[0021] As described in more detail with reference to Fig. 3, the insulation resistance tester 100 includes a propagation velocity unit 142, which may be a standalone module or combined with other components of the tester, depending on implementation. The propagation velocity unit 142 may take different forms, depending on embodiments of the insulation resistance tester 100. In one embodiment the propagation velocity unit 142 uses time-domain reflectometry (TDR), which involves generating and sending an energy pulse through the port 102 and the test cables 132 to the CUT 130. The pulse may have a voltage of between 10 Volts - 300 Volts, for example. Then, the propagation velocity unit 142 measures and analyzes a reflection of the pulse as it returns from the CUT 130 and is sensed by the insulation resistance tester 100. Comparing qualities of the return pulse, such as amplitude, and time delay, to the known outgoing pulses generated by the propagation velocity unit 142 allows the insulation resistance tester 100 to determine and measure the propagation speed of the CUT 130 for the particular environmental testing conditions when the CUT is tested. The propagation velocity unit 142 is also coupled to a propagation velocity database 143, which stores the measured propagation velocities as well as other information, including environmental information, as described below. In operation, the propagation velocity unit 142 effectively creates the propagation velocity database by generating propagation velocity measurements that may be associated with environmental conditions and stored in the propagation velocity database 143.

[0022] The insulation resistance tester 100 also includes either or both a temperature processor 144 and humidity processor 148, which are coupled to the environmental sensing ports 104 as well as the one or more measuring units 140. Further, the temperature processor 144 may be coupled to and acquire information from the propagation velocity database 143 as well. In operation, as described in detail below, the temperature processor 144 may modify a resistance measurement made by the one or more measuring units 140 to make a temperature compensated measurement. In general, the temperature processor 144 applies a temperature correction factor to the original, or raw, insulation resistance measurement made through the measurement ports 102 to make a compensated measurement. The compensated measurement is generally more accurate than the raw measurement becausethe compensated measurement accounts for the environmental temperature or temperature of the CUT 130 during the raw insulation resistance measurement. The temperature processor 144 may be implemented by a numerical calculator pre-loaded with a temperature compensation formula, or a look-up table stored in memory, for example. The temperature processor 144 may use either the temperature information acquired by the temperature probe 150 (or multiple probes 150) or the temperature information provided by the aimable temperature sensor 170, in making its calculations. In other embodiments, the temperature processor 144 may use an average or weighted average of the output of the temperature probe 150 and temperature sensor 170. Details of the temperature processor 144 in conjunction with the propagation velocity unit 142 and propagation velocity database 143 are discussed with reference to Fig. 3, below.

[0023] Either the or both of the temperature processor 144 and the humidity processor 148 may be used by the insulation resistance tester 100 to generate alerts for the user. For example, when the humidity sensor 160 measures a rather high relative humidity, the humidity processor 148 may create a warning to the user that measurements made under such high humidity conditions may be inaccurate. Or the humidity processor 148 may be used in conjunction with the temperature processor 144 to determine whether the CUT 130 is at or approaching a dew point of the environment. The dew point may be reached when the temperature of an object is less than, or even significantly less than the ambient air temperature. The temperature difference between an object and the ambient air temperature to reach the dew point is dependent on the relative humidity. As described above, the temperature probe 150 may be used to measure the ambient air temperature, while the temperature sensor 170 may be used to measure the temperature of the CUT 130, and the humidity sensor is structured to determine the amount of relatively humidity. Thus, all of the data inputs used to determine dew points are available to the temperature processor 144 and humidity processor 148. Then, by storing a dew point table in either the temperature processor 144 or the humidity processor 148, embodiments of the disclosure may generate a warning if there is a possibility that a dew point of any measured object may be reached.

[0024] The insulation resistance tester 100 further includes one or more main processors 110 configured to execute instructions stored in a main memory 111 and may perform any methods and / or associated steps indicated by such instructions. For instance, the processorexecutes these software instructions and other procedures to operate a menu on a display 122 of the insulation resistance tester 100. A user of the insulation resistance tester 100 uses the menu to control the operation of the resistance tester, such as by setting parameters, running tests, and directing how the results are to be used. The one or more main processors 110 operate most or all functions of the insulation resistance tester 100.

[0025] User inputs 120 are coupled to and act as input for the one or more processors 110, and may include buttons, a keyboard, touchscreen, and / or any other controls employable by a user to interact with the insulation resistance tester 100. The display 122 may be a monochrome or digital screen such as an LCD, LED, OLED, or any other monitor to display output of the insulation resistance tester 100. In some embodiments, data or images from the display 122 of the resistance tester 100 may be made available to other devices through an information cloud 124 or other type of communication network.

[0026] While the components and functions of the insulation resistance tester 100 are depicted and described above, it will be appreciated by a person of ordinary skill in the art that any of these components can be combined or integrated into fewer component parts, or different functions may be split into components in addition to the functional blocks illustrated in Fig. 1. In particular, the temperature processor 144 and humidity processor 148 may be disposed in a single device, processor, or module, or may be fully incorporated into the one or more measurement units 140, for example. In yet other embodiments the function of the temperature processor 144 and humidity processor 148 may be performed by the one or more processors 110 that control the operation of the insulation resistance tester 100.

[0027] Fig. 2 illustrates an insulation resistance measurement system 200 that includes the insulation resistance tester 100 of Fig. 1, and also illustrating the testing cables 132, CUT 130, one or more temperature probes 150, humidity sensor 160, and the aimable temperature sensor 170 all described with reference to Fig. 1.

[0028] The insulation resistance measurement system 200 of Fig. 2 further includes a mobile device 240 that is coupled to the insulation resistance tester 100. The mobile device 240 may be a mobile phone, tablet computer, laptop computer, or other computing device structured to interact with the insulation resistance tester 100. In some embodiments the mobile device 240 is coupled to the insulation resistance tester 100 through communication wires (not illustrated), while in other embodiments the mobile device is wirelessly coupled tothe insulation resistance tester, such as through a WiFi, Bluetooth™, or other wireless data protocol.

[0029] Although in Fig. 2 the measurement probes 150, 160, 170 are illustrated as being in direct communication with the insulation resistance tester 100, it is possible that any or all of the measurement probes communicate with and provide data directly to the mobile device 240, which may convey such measurement information to the insulation resistance tester 100. In some embodiments both the mobile device 240 and the insulation resistance tester 100 each include a set of measurement probes 150, 160, 170 or other sensors used to measure the environment around both the insulation resistance tester and the mobile device 240.

[0030] In operation, the mobile device 240 and insulation resistance tester 100 cooperate to perform tests and measurements on the CUT 130, including temperature compensated measurements described with reference to Fig. 1. The user of the measurement system 200 may control the system by interacting with either the mobile device 240 or the insulation resistance tester 100. A touch screen 244 on the mobile device 240 may be controlled by one or more processors 250 running programs stored on affiliated memory 251 to present an interactive user interface to the user. Then, by interacting with the touch screen 244, the user can control which tests and which test parameters will be used by the insulation resistance tester 100 to generate tests and make measurements of the CUT 230. Or, in other embodiments, the user inputs to the insulation resistance tester 100 may be controlled by the user to initiate and perform various tests on the CUT and the results of the tests may be shown on display screens located on either or both the insulation resistance tester 100 and the mobile device 240. In some embodiments the mobile device 240 may be used to remotely start and / or stop tests being performed on the insulation resistance tester 100. The details of menus, displays, etc. of the measurement system 200 are largely implementation specific. But, in general, a user may interact with either the mobile device 240 or the insulation resistance tester 100 of the measurement system 200 to perform measurements and tests of the CUT 230 and the results of such measurements and / or tests may be displayed on either device. And, although the measurement system 200 of Fig. 2 includes a mobile device 240 to provide a user of the system with additional controls, inputs, and outputs, it is not necessary that that mobile device 240 be present to operate the insulation resistor tester 100, and instead the insulation resistor tester may be operated solely on its own to test the CUT 230.

[0031] One benefit of acquiring environmental data about the testing environment is that the environmental data may be captured and stored along with the insulation resistance test data generated by the insulation resistance tester 100. In other words, data along with the actual insulation resistance may be part of a test report for the user. Thus, the test report may include information such as date, time, location of the test, user identification, ambient temperature, ambient humidity, and CUT temperature, in addition to the actual measured insulation resistance and potentially compensated insulation resistance determined by the temperature processor 144 (Fig. 1). Further, any warnings that were made in conjunction with information from the humidity sensor 160 may also appear in the test report. Also, as mentioned above, the test report may be stored through a communication network 124 to make a permanent record of the measurements. Then, as future measurements are made, they may be stored with the previous measurements so that measurements may be viewed over time to determine if the measured insulation resistance of the CUT 130 is changing over time. The measurements may also include not only temperature-compensated measurements as described above, but also may include a compensation made to a standard, such as 40° C. In some embodiments all of the various measurements are kept in the measurement record or report, including raw (measured) insulation resistance, resistance compensated for ambient temperature, raw resistance converted to a standard temperature measurement, and the resistance compensated for ambient temperature and also converted to a standard temperature measurement. This last measurement, which includes compensation for ambient temperature as well as a conversion to a standard temperature may be the most accurate measurement of a CUT to evaluate over time. Environmental data of the measurement may be kept in the test record as well, such as ambient temperature, ambient humidity, and temperature of the CUT.

[0032] In addition to generating a detailed record of the measurement, embodiments according to the disclosure may display ambient conditions on a measurement screen either on the insulation resistance tester 100 or the mobile device 240 (Fig. 2). Further, embodiments may generate and display alerts or warnings to inform the user when an accuracy of the resistance measurement may be negatively affected by testing environment conditions.

[0033] Fig. 3 is a chart of a flow 300 illustrating example operations that may be performed in the insulation resistance tester 100, and specifically in a system that includes apropagation velocity unit 142, or similar functionality. As described above, the propagation velocity unit 142 sends a signal, such as a time domain reflection signal to the CUT 130, and analyzes a return signal. By comparing properties of the return signal to the signal that was originally sent, the propagation velocity unit 142 determines the propagation velocity of the CUT 130. Operation 310 describes this action as describing a baseline propagation velocity measurement of the CUT 130. Then the insulation resistance tester 100 measures the value of the resistance of the insulation in the CUT 130 in an operation 320. The propagation velocity of the CUT 130 determined with the baseline measurement of operation 310 is stored in an operation 330. In some embodiments the temperature measurement performed in operation 320 may also be stored along with or in association with the propagation velocity measurement.

[0034] An operation 340 in the flow 300 measures the propagation velocity of the same CUT 130 at a later time than that measured in operation 310. The time of operation 340 is indicated as time 1+n, and may be long enough after the time of operation 310 that the environmental conditions of the CUT 130 have changed. For instance the operation 340 may be later in the same day, or on a different day that was the operation 310. In some cases, there may be weeks, months, or even years between the velocity measurements of operations 310 and 340. As will be described below, since the propagation velocities determined by the propagation velocity unit 142 for the CUT 130 are used to populate a propagation database 143 (Fig. 1), accuracy of the compensated resistance measurement made by the insulation resistance tester 100 increases as more measurements that are made in various environmental conditions and stored in the propagation database 143. In the flow 300, the loopback 365 indicates that the operations 340, 350, and 350 may be repeated multiple times to increase the number of entries stored within the propagation database 143.

[0035] Returning back to operation 340, a new propagation velocity measurement is made of the CUT 130. And the resistance of the CUT 130 is measured at the same time, 1+n, in an operation 350. Then the propagation velocity made at time 1+n is also stored in the propagation database 143 in an operation 360. As mentioned above, in some embodiments the resistance measured in the operation 350 may also be stored in or associated with the measured propagation velocity that was recorded in operation 360.

[0036] Because a difference in propagation delay has a direct tie to a change in temperature, a temperature compensation may be made to the resistance measurementmade in operation 350. In other words, knowing a differential in propagation delay between an instant measurement and the baseline measurement allows the insulation resistance tester 100 to determine by what factor the resistance measurement should be temperature compensated to be most accurate.

[0037] The propagation velocity variation between different temperatures is different for cables having different types of insulation materials. In fact, some propagation velocities increase with increased temperatures for some materials while decreasing for others. Therefore, the insulation resistance tester 100 accepts input from the user to determine which type of insulation is found on the CUT 130 prior to making the compensation adjustment in operation 370. Additionally, the velocity propagation database 143 also stores the insulation type along with the velocity propagation measurements. Over time, as the velocity propagation database 143 gets additional entries, the accuracy of the compensation measurement based on velocity propagation improves. Also, the velocity propagation database 143 from a particular insulation resistance tester 100 may be shared with other resistance testers. Or, in some embodiments, measurements from multiple insulation resistance testers may be combined in a central repository and shared amongst all of the units. In some embodiments the velocity propagation delay figures may be normalized to a particular temperature, such as 40° C.

[0038] One benefit of the compensation made using the velocity propagation is that, unlike other embodiments described above, the change in velocity propagation is a direct result of the temperature change of the CUT 130 itself. Recall from above that some temperature compensation methods may use data averaged from a geographic area, or an above-ground temperature. In contrast, the temperature compensation described with reference to Fig. 3 uses the actual temperature of the CUT 130 itself and may be more accurate than other temperature compensation methods.

[0039] Fig. 4A illustrates an example display screen 400 that may be presented to the user on either or both of the insulation resistance tester 100 and the mobile device 240. In other embodiments, the display screen 400 showing ambient testing environment data may be shown on the mobile device 240, while measurement results are displayed on the insulation resistance tester 100. With reference to Fig. 4A, the display screen 400 includes a simulated meter of a resistance measurement. An arrow indicator shows the measurement is in the Megaohms range, and that the resistance measurement passes the standard measurementtest. A "Pass" indication is highlighted to further enforce the measurement outcome. The insulation resistance measurement is shown in text form. Also, temperature and humidity information are presented in the example display screen 400 to inform the user of ambient testing conditions. As described above, the ambient testing conditions may also be recorded in the test record. Although the display screen 400 presents the ambient testing conditions to the user, no other changes from a standard display screen of the insulation resistance tester 100 are made on the screen illustrated in Fig. 4A.

[0040] Fig. 4B illustrates another example display screen 402 that may be presented to the user on either or both of the insulation resistance tester 100 and the mobile device 240. With reference to Fig. 4B, the display screen 402 includes all of the information that the example display screen 400 contained, including the simulated meter, text display of the raw measurement, and ambient test conditions. The display screen 402, however, further includes a compensated resistance measurement in addition to the raw measurement. Specifically, in this example, the raw measurement was 10.0 Megaohms, which is the same as in Fig. 4A. In Fig. 4B, however, a compensated measurement of 25.0 Megaohms is also displayed on the display screen 402, and the meter indicates the compensated measurement. The resistance measurement compensation to generate the compensated measurement display was performed based on the temperature measurement in any of the manners described above.

[0041] Fig. 5A shows an example display screen 500 that contains an alert that may be presented to the user on either or both of the insulation resistance tester 100 and the mobile device 240. This alert on the display screen 500 is based on a high relative humidity reading by the humidity sensor 160 (Fig. 1). Embodiments of the disclosure generate the alert when the humidity of the testing environment detected by the humidity sensor 160 could affect the accuracy of the insulation resistance measurement. The display screen includes a text-based alert 502, as well as a color-based alert 504. The color-based alert 504 may have several levels, such as green, yellow, and red. The insulation resistance measurement is still shown on the example display screen 500, but the alerts 502 and 504 indicate to the user that the insulation resistance measurement may not be accurate, and testing on another day, under different conditions, may be advised.

[0042] Fig. 5B shows an example display screen 520 that is similar to the display screen500, except that a color-based alert 524 indicates that the sensed humidity level was withina standard range for accurate measurement. A text-based measurement 526 shows a temperature-compensated resistance measurement to the user.

[0043] Fig. 6 is an example display screen 600 illustrating an environmental condition warning 610 that may be presented to a user of the insulation resistance testing system of Fig. 2, according to embodiments. Similar to the environmental warning screens illustrated above, the display screen 600 provides a warning 610 to the user when the insulation resistance measurements made from the insulation resistance tester 100 may not be the most accurate, due to the environmental conditions. The warning 610 shown in Fig. 6 provides additional detail to the user in the form of a graph of the temperature and humidity of the testing environment over a period in the past. In this example the graph shows several hours of data, where both a temperature and humidity have risen over time. The warning 610 of Fig. 6 provides significant data to the user about the environmental conditions of the testing area, and allows the user to quickly understand if a measurement made at the present time will be sufficiently accurate.

[0044] Fig. 7 is another example display screen 700 illustrating an environmental condition warning that may be presented to a user of the insulation resistance testing system of Fig. 2, according to embodiments. The display screen 700 provides a warning area 710 showing a portion of a timescale where the temperature and / or humidity readings in the testing environment were determined by the insulation resistance tester 100 as possibly leading to inaccurate results. Illustrated in the display screen 700 are two data graphs, 720, 730, that show a historical record of temperature and humidity, respectively. The time scale, i.e., x axis, of the display screen 700 may be of any scale, such as hours, weeks, or years. Data markers on the display screen 700 show both a measured resistance 750 and a temperature compensated resistance 752 for various times when the CUT 130 has been measured, although not all data points in Fig. 7 are labeled to preserve clarity. The temperature and humidity graphs 720, 730 are also shown for each measurement, concatenated as a line. The temperature and humidity graphs 720, 730 may be discontinuous in some displays.

[0045] Importantly on the display screen 700, the warning area 710 highlights a time period when the combination of temperature and humidity, both being high in the illustrated case, combine so that the measured resistance and temperature compensated resistance may have less accuracy than had the resistance measurement been made at a time when the environmental factors were closer to average. Poor environmental conditions that may affectresistance measurements may include high temperatures and a combination of temperature and humidity near the dew point. Referring back to Fig. 7, note how the temperature compensated resistance data point 752 is significantly further from the measured resistance data point 750 within the warning area 710, indicating that the resistance measurement may be inaccurate.

[0046] Although several sample display screens are illustrated herein, embodiments of the disclosure may generate any type of alert for the user based on ambient conditions, such as low temperature, high temperature, low humidity, high humidity, dew point calculations, and other situations in which the ambient testing environment may affect the measurement. In addition, temperature compensations may be made based on ambient temperature as well as corrections to a standard temperature may be made. Display screens may illustrate any or all of these compensations and corrections, as well as the warnings based on testing conditions described above. Further, and also as described above, reports including all of the data recorded, measured, or calculated by the insulation resistance tester 100 described above may appear in reports generated as a test summary, and stored offline for later use.

[0047] As described above, the insulation resistance tester according to embodiments of the disclosure includes multiple advantages over the state of the art. The disclosed insulation resistance tester may include ambient temperature, device temperature, and ambient humidity sensors to automatically record environmental conditions and associate them with tests made under those conditions. The insulation resistance tester may also automatically compensate the insulation resistance measurements for temperature using compensation formulas, and also correcting the compensated measurements to standard measurement numbers. The insulation resistance tester provides additional information and higher quality measurements than existing solutions.

[0048] The previously described versions of the disclosed subject matter have many advantages that were either described or would be apparent to a person of ordinary skill. Even so, these advantages or features are not required in all versions of the disclosed apparatus, systems, or methods.

[0049] Additionally, this written description makes reference to particular features. It is to be understood that the disclosure in this specification includes all possible combinations of those particular features. Where a particular feature is disclosed in the context of a particularaspect or example, that feature can also be used, to the extent possible, in the context of other aspects and examples.

[0050] Also, when reference is made in this application to a method having two or more defined steps or operations, the defined steps or operations can be carried out in any order or simultaneously, unless the context excludes those possibilities.

[0051] Although specific examples of the invention have been illustrated and described for purposes of illustration, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, the invention should not be limited except as by the appended claims.

Claims

CLAIMS:

1. An insulation resistance tester, comprising: a set of testing cables structured to be coupled to a device under test; a measurement port coupled to the set of testing cables; a resistance measurement unit structured to determine a resistance measurement of the device under test by sending a signal from the measurement port and receiving a return signal from the measurement port; an environmental port structured to receive an input from an environmental sensor; a temperature compensator structured to modify the resistance measurement based on the input received from the environmental sensor; and a display structured to show an indication of the modified resistance measurement.

2. The insulation resistance tester according to claim 1, in which the environmental port receives input from a temperature sensor.

3. The insulation resistance tester according to claim 2, in which the temperature sensor is wired or wireless.

4. The insulation resistance tester according to claim 2, in which the temperature sensor is a wireless infrared temperature sensor.

5. The insulation resistance tester according to any of the preceding claims in which the environmental port receives input from a humidity sensor.

6. The insulation resistance tester according to any of the preceding claims further comprising a propagation velocity unit structured to determine a change in velocity propagation of the device under test compared to a baseline propagation velocity.

7. The insulation resistance tester according to claim 6, further comprising a propagation velocity database into which the propagation velocity unit stores data.

8. The insulation resistance tester according to claims 6 or 7, further comprising a temperature compensator structured to compensate the resistance measurement based on data generated by the propagation velocity unit.

9. The insulation resistance tester according to any of claims 5 - 8, further comprising storing data generated by the propagation velocity unit on a remote device.

10. The insulation resistance tester according to any of the preceding claims further comprising an alert generator structured to generate a warning on the display when input received from the environmental sensor is above a threshold value.

11. The insulation resistance tester according to claim 10, in which the warning is shown in color.

12. The insulation resistance tester according to claim 10, in which the warning includes historical temperature data.

13. The insulation resistance tester according to claim 10, in which the warning includes historical temperature data and historical humidity data.

14. The insulation resistance tester according to any of the preceding claims in which the display shows the resistance measurement and the modified resistance measurement.

15. The insulation resistance tester according to any of the preceding claims in which the temperature compensator comprises a formula or a stored lookup table.

16. The insulation resistance tester according to any of the preceding claims further comprising a memory to store a historical record of the resistance measurement and any prior resistance measurements made for the same device under test.

17. A method performed by an insulation resistance tester coupled to a device under test, the method comprising: performing a resistance test on the device under test; receiving an environmental input from an environmental sensor coupled to the insulation resistance tester; and compensating the results of the resistance test by an amount related to the environmental input to generate a compensated resistance measurement.

18. The method according to claim 17, in which receiving an environmental input comprises receiving a temperature input.

19. The method according to claims 17 or 18, in which the temperature sensor is wired or wireless.

20. The method according to claims 17 or 18, in which the temperature sensor is a wireless infrared temperature sensor.

21. The method according to claims 17-20, in which the environmental port receives input from a humidity sensor.

22. The method according to any of the preceding claims further comprising operating a propagation velocity unit to determine a change in velocity propagation of the device under test compared to a baseline propagation velocity.

23. The method according to claim 22, further comprising storing data generated by the propagation velocity unit into a propagation velocity database.

24. The method according to claims 22 or 23, further comprising compensating the resistance measurement based on data generated by the propagation velocity unit.

25. The method according to claims 23-24, further comprising storing data generated by the propagation velocity unit on a remote device.

26. The method according to claims 17 - 25, further comprising generating a warning when input received from the environmental sensor is above a threshold value.

27. The method according to claim 26, further comprising generating the warning in color.

28. The method according to claims 26 or 27, in which generating the warning comprises generating historical temperature data and presenting it to a user.

29. The method according to claim 28, in which generating the warning comprises generating historical temperature data and historical humidity data and presenting them to a user.

30. The method according to any of the claims 17-27, further comprising displaying the resistance measurement and the modified resistance measurement.

31. The method according to claims 26 or 27, in which generating the warning comprises generating historical temperature data and presenting it to a user.

32. The method according to any of claims 17 - 31, in which compensating the results of the resistance test comprises computing a result according to a pre-stored formula or retrieving a result from a stored lookup table.

33. The method according to any of claims 17 - 32, further comprising storing a historical record of the resistance measurement and any prior resistance measurements made for the same device under test in a memory.

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