Test method and apparatus

Abstract

Measurement apparatus is operated to perform a test of an electrical parameter of a device under test, the test comprising providing a voltage to the device under test (103), the measurement apparatus comprising an electrical tester (102) for connection to the device under test (103) and user equipment configured (101) to control the electrical tester (102) using a communication link (111). A first test is started in response to a first user interaction and the communication link (111) is checked while the first test is in progress. The first test is aborted if a check of the communication link (111) indicates that the communication link has failed, wherein aborting the first test comprises, without user intervention, stopping providing the voltage to the device under test (103).

Description

[0001] Test Method and Apparatus

[0002] Technical Field

[0003] The present invention relates generally to a method and apparatus for performing a test of an electrical parameter of a device under test, the test comprising providing a voltage to the device under test, the measurement apparatus comprising an electrical tester for connection to the device under test and user equipment configured to control the electrical tester using a communication link, and in particular, but not exclusively, to performing a safety critical remote controlled test of a portable appliance.

[0004] Background

[0005] It is conventional for measurement apparatus to provide a voltage to a device under test in order to test one or more electrical parameters of the device. The test may be safety critical, in that the voltage may energise the device under test and cause it to present a mechanical hazard to the operator, for example by causing a component of the device to rotate, or the voltage may be dangerous to an operator. For a safety critical test, it may be required that the operator is able to abort the test while the test is in progress so that the voltage is no longer presented to the device under test. It would be advantageous to provide a remote control for the measurement equipment, for the convenience and potential increased safety of the operator, by allowing the operator to be more distant from the device under test. However, a remote control may introduce a hazard, in that a safety critical test may be inadvertently started by unintended contact with the remote control, and in that communication between the remote control and the measurement equipment may be unreliable so that the operator is unable to abort a test once the test has started.

[0006] Summary

[0007] In accordance with a first aspect, there is provided a method of operation of measurement apparatus for performing a test of an electrical parameter of a device under test, the test comprising providing a voltage to the device under test, the measurement apparatus comprising an electrical tester for connection to the device under test and user equipment configured to control the electrical tester using a communication link, the method comprising: configuring the user equipment to be capable of causing the electrical tester to start a first test in response to a first user interaction with the user equipment; starting the first test in response to the first user interaction; checking the communication link while the first test is in progress; and aborting the first test if a check of the communication link indicates that the communication link has failed, wherein aborting the first test comprises, without user intervention, stopping providing the voltage to the device under test.

[0008] Checking the communication link while the first test is in progress and aborting the test if the communication link has failed provides increased safety to an operator by preventing the test from taking place if the operator is unable to abort the test manually by interacting with the user equipment.

[0009] In an example, the method comprises checking the communication link by sending a sequence of test messages from the electrical tester to the user equipment, sending a response to each test message received at the user equipment from the user equipment to the electrical tester and generating an indication that the communication link has failed if a response is not received at the electrical tester for a test message; and aborting the first test in response to the indication that the communication link has failed.

[0010] This method provides a reliable indication that the communication link has failed so that the test can be stopped with a low false alarm rate and a high probability of detecting a link failure.

[0011] In an example, the method comprises sending the test messages in the sequence of test messages at regular intervals of time.

[0012] This method limits the period of time that the communication link can fail without detection of the failure.

[0013] In an example, the method comprises sending the test messages with a spacing in time of less than one second. This method provides for efficient operation of the communication link while providing a sufficiently rapid response to a failure of the communication link to provide safe operation.

[0014] In an example, each test message comprises an identifier of the test message to distinguish the test message from other test messages in the sequence, and wherein each response comprises the identifier of the test message which caused the response.

[0015] This method allows a reliable check that each test message has been successfully received in both directions of the link. Link failure can be detected if a response to any of the test messages is not received.

[0016] In an example, the first user interaction comprises two separate actions of the user in interaction with a touch sensitive screen.

[0017] This method reduces the probability that the first test can be inadvertently started by contact with the user equipment.

[0018] In an example, the first user interaction comprises a user touching a predefined part of the touch sensitive screen, and then touching the screen to move a slider across the screen. In an example, the first user interaction comprises moving the slider to follow a track having a non-linear shape. This reduces the probability that the user interaction can be performed accidentally.

[0019] In an example, the first test is a safety critical test. For example, the voltage provided to the device under test may be a mains voltage and the device under test may be energised by the mains voltage. This may present a hazard to an operator by causing operation of the device under test, for example by causing a component of the device under test to rotate or to present some other hazard due a fault in the device under test.

[0020] In an example, the voltage provided to the device is applied to a mains socket on the electrical tester to power the device under test. The mains socket allows convenient testing of a mains powered portable appliance.

[0021] In an example, powering the device under test causes a risk to an operator of the measurement apparatus and the user equipment is configured to generate a warning that the appliance may operate before allowing said first user interaction with the user equipment. This method provides an additional degree of safety by alerting the operator to the risk that the test may need to be aborted if a safety hazard is observed.

[0022] In an example, the device under test is an insulator, and the electrical tester provides a hazardous live output to test leads for connection to the insulator.

[0023] In an example, the method comprises performing a series of tests of the device under test under control of the user equipment, wherein the series of tests comprises the first test as a safety critical test and a non-safety-critical test, wherein the user equipment is configured to cause the electrical equipment to perform the non-safety-critical test without requiring the first user interaction. This method allows for efficient operation of the measurement equipment by allowing a less onerous procedure than the first user interaction for starting a non- safety-critical test, and reducing the chance that the user becomes accustomed to performing the first interaction and thereby becomes more likely to perform the first interaction inadvertently.

[0024] In an example, the method comprises configuring the user equipment to be capable of causing the electrical tester to be capable of causing an abortion of the first test while the first test is in progress in response to a second user interaction with the user equipment. In an example, the second user interaction comprises touching a second predefined part of a touch sensitive screen. The second interaction can be made easier to perform than the first interaction, so that the test can be reliably aborted in the event of a safety hazard.

[0025] In accordance with a second aspect, there is provided an electrical tester for use in measurement apparatus for performing a test of an electrical parameter of a device under test, the test comprising providing a voltage to the device under test, the measurement apparatus comprising the electrical tester for connection to the device under test and a user equipment configured to control the electrical tester using a communication link, the electrical tester comprising: a voltage interrupter controllable to prevent the electrical tester from providing the voltage to the device under test; a wireless transceiver configured to provide the communication link with the user equipment; and one or more processors configured to: start a first test in response to an indication from the user equipment of a first user interaction with the user equipment; and check the communication link and abort the test, by causing the voltage interrupter to prevent the electrical tester from providing the voltage to the device under test in response to a communication link failure.

[0026] In an example, the voltage interrupter comprises one or more relays. The voltage interrupter may be configured for connection to an external power source, such as a source of mains voltage. In an example, the voltage provided to the device under test is a mains voltage and the device under test is energised by the mains voltage. The electrical tester may comprise a mains socket and the voltage provided to the device may be applied to the mains socket on the electrical tester to power the device under test.

[0027] In an example, the voltage interrupter is implemented by functions of a voltage generator that may be switched on or off. The voltage generator may generate voltages which are different from the mains voltage, for example the voltage generator may generate a DC (direct current) voltage and may generate a high voltage of a kilovolt or greater, for example for insulation testing.

[0028] In accordance with a third aspect, there is provided a system comprising an electrical tester as claimed and a user equipment configured as a remote control adapted to receive and respond to a communication link test signal generated by the electrical tester. In an example, the system is configured to perform the claimed method.

[0029] Further features and advantages will be apparent from the following description of exemplary embodiments, which are given by way of example only.

[0030] Brief Description of the Drawings

[0031] Figure 1 is a schematic diagram showing measurement apparatus comprising an electrical tester and a user equipment configured as a remote controller for the electrical tester, the electrical tester providing a voltage to a device under test; Figure 2 is a schematic diagram showing measurement apparatus in which the electrical tester is configured to test a portable electrical appliance, and the electrical tester has a mains socket to which the electrical tester applies a voltage;

[0032] Figure 3 is a schematic diagram showing measurement apparatus in which the electrical tester is configured to test an insulator, and the electrical tester is configured to apply a test voltage to the insulator via test leads;

[0033] Figure 4 is a schematic diagram illustrating an electrical tester connected to a user equipment by a Bluetooth or Bluetooth Low Energy communication link, in which a series of test messages are transmitted from the electrical tester and a response to each test message is transmitted from the user equipment as a check of the communication link;

[0034] Figures 5A to 5F illustrate a sequence of displays on the user equipment showing the stages of starting a series of tests and aborting of a test under manual control or when a check of the communication link shows a link failure;

[0035] Figure 6 is a flow diagram of a method of operating the measurement apparatus; and

[0036] Figure 7 is a flow diagram of a further method of operating the measurement apparatus.

[0037] Detailed Description

[0038] By way of example, embodiments will now be described in the context of measurement apparatus for performing a Portable Appliance Test (PAT) under remote control by user equipment such as a mobile phone, a tablet or a personal computer. Embodiments are also described where the measurement apparatus is for performing an insulation test by generating a voltage and providing this to test leads for connection to an insulator. It will be understood that the embodiments described are examples, and that other embodiments may be provided in which the test equipment provides a voltage to a device under test to perform other types of electrical test.

[0039] A PAT test is used to verify several safety parameters of a device under test such as: insulation resistance (live to earth), bonding resistance (of the earth connection), leakage current, and Residual Current Device (RCD) operation, for example. PAT testing is typically carried out for all mains-powered equipment in an office or a commercial facility, such as kettles, printers, monitors, extension leads, etc. The PAT testing is typically annual, so each such tester cooperates with a large database of equipment which was already tested, as well as auxiliary equipment such as barcode printers and scanners to speed up the process of data retrieval and storage. The most complex PAT testers have the databases built into them. The simpler PAT testers just perform the tests and the database functionality is provided by alternative means.

[0040] In PAT testing there are tests which are not dangerous, such as the continuity test which just measures resistance of earth connections by applying safe, low voltage (< 30 V), or even the insulation test which generates up to 600 V but it has limited output current such that it is not dangerous (not classified as “hazardous live”). Therefore, such tests may be described as safety non-critical, which may be also referred to as non-safety-critical. However, in one specific type of test the device under test is powered through the PAT tester. The PAT tester itself does not generate the power, but rather channels mains power through the mains socket available on the tester. The mains power is enabled by internal relays, such as electromechanical or solid-state switches, which connect an external source of mains power (electricity supply having a voltage of typically 230V AC or 120V AC) to the mains socket under control of a processor in the PAT tester. The purpose of this test is to measure leakage current, which quantifies the quality of insulation from the hazardous live connections (Live, Neutral) to the Earth. This leakage current can be measured in a number of ways, and in one specific test the L + N conductors are fed through a differential current transformer which measures the net of the L+N current. If there is no leakage, then the sum is zero. If there is some leakage this is detected by the differential current transformer. During such a test the equipment under test which is connected to the PAT tester will become energised. This can mean immediate danger to the operator, especially in cases when the tested appliance can move violently (e.g. impact drill, floor polisher) or become dangerous by different means (e.g. hot plate hob, pressure washer, welder). In this case the test is safety critical because the danger does not arise just from the presence of voltage as such, but rather from a secondary action that can be delivered by the powered-up equipment under test.

[0041] For the safety-critical test, the operator is able to abort the test while the test is in progress so that the voltage is no longer presented to the device under test.

[0042] In the embodiments described, a remote control is provided for the electrical tester, in this example a PAT tester, for the convenience and potential increased safety of the operator, by allowing the operator to be more distant from the device under test. The remote control is implemented by user equipment, such as a mobile phone, tablet or personal computer, which is connected to the electrical tester by a wireless link such as a Bluetooth or Bluetooth Low Energy link. However, a remote control may potentially introduce a hazard, in that a safety critical test may be inadvertently started by unintended contact with the remote control, and in that communication between the remote control and the measurement equipment may be unreliable so that the operator is unable to abort a test once the test has started.

[0043] In order to reduce the probability of inadvertently starting a test by unintended contact with the user equipment, the user equipment is configured, for example by a suitable application (app) running on a processor in the user equipment, to be capable of causing the electrical tester to start a test in response to a first user interaction with the user equipment. In an example, the first user interaction comprises two separate actions of the user in interaction with a touch sensitive screen, which reduces the probability that the first test can be inadvertently started by contact with the user equipment. In an example, the first user interaction comprises a user touching a predefined part of the touch sensitive screen, such a button icon, and then touching the screen to move a slider across the screen. The slider may follow a linear track, or the first user interaction may comprise moving the slider to follow a track having a non-linear shape. This reduces the probability that the user interaction can be performed accidentally. In order to reduce the probability that an operator is unable to abort a test once the test has started, the measurement equipment automatically checks the communication link while the test is in progress and aborts the first test if a check of the communication link indicates that the communication link has failed. Aborting the first test comprises, without user intervention, stopping providing the voltage to the device under test, providing increased safety to an operator by preventing the test from taking place if the operator is unable to abort the test manually by interacting with the user equipment.

[0044] Figure 1 shows measurement apparatus comprising an electrical tester 102 and a user equipment 101 configured as a remote controller for the electrical tester 102, the electrical tester 102 providing a voltage to a device under test 103. The user equipment 101 is configured to control the electrical tester 102 using a communication link 111. The communication link 111 is provided between a wireless transceiver 107 in the electrical tester 102 and a wireless transceiver 105 in the user equipment. The wireless link may be, for example, a Bluetooth or Bluetooth Low Energy link, or a link using another wireless protocol, or an infrared link, for example. The wireless link may also be implemented via an external network, for example the electrical tester 102 and the user equipment 101 may be connected to a Wi-Fi access point, or may be connected by a cellular radio link, or by a combination of the two. In this example, the user equipment has a touch sensitive screen 104 with which the user may interact with the user equipment, for example by the first user interaction, which may involve a predefined sequence of tapping and swiping actions to start a safety-critical test. The user equipment has one or more processors 106 connected to the touch sensitive screen 104 and the wireless transceiver 105, to control operation of the user equipment according to computer-readable instructions held in memory in the user device, for example an application program for controlling the electrical tester.

[0045] The electrical tester 102 comprises a voltage interrupter 110 which is controllable to prevent the electrical tester 102 from providing a voltage to the device under test 110. The voltage interrupter 110 may comprise one or more relays which may connect or disconnect a voltage provider 109 to the device under test 103. The voltage provider 109 may simply be a connection to an external power source such as a mains supply, or may be a voltage generator. The voltage generator and voltage interrupter 110 may be implemented by a single unit, in which a voltage generator is controllable to provide or not to provide an output voltage. One or more processors 108 are configured to control the electrical tester 102 and to start a first test in response to an indication from the user equipment 101 of a first user interaction with the user equipment and to check the communication link and abort the test, by causing the voltage interrupter 110 to prevent the electrical tester 102 from providing the voltage to the device under test 103 in response to a communication link failure.

[0046] Figure 2 shows measurement apparatus in which the electrical tester 202 is configured as a PAT tester to test a portable electrical appliance 203, and the electrical tester 202 is provided with a mains socket 213 to which the electrical tester 202 applies a voltage during a first test. In the arrangement of Figure 2, the voltage interrupter 210 is configured for connection to an external power source, such as a source of mains voltage, so that the voltage provided to a plug 212 of the device under test 203 is a mains voltage and the device under test 203 is energised by the mains voltage. The user equipment has a touch sensitive screen 204, a processor 206 and a wireless transceiver 205 with similar functions to the corresponding features of Figure 1, and the electrical tester also has a wireless transceiver 207 similar functions to the corresponding features of Figure 1.

[0047] Figure 3 shows measurement apparatus in which the electrical tester 302 is configured to test an insulator 303, and the electrical tester 302 is configured to apply a test voltage to the insulator 303 via test lead connections 314 and test leads 315, 316. The user equipment 301 has a touch sensitive screen 304, a wireless transceiver 305, and a processor 306 with similar functions to the corresponding features of Figures 1 and 2. In this example, the voltage interrupter is implemented by functions of a voltage generator 310 that may be switched on or off. The voltage generator may generate a DC (direct current) voltage and may generate a high voltage of a kilovolt or greater, for insulation testing. In this case, the voltage generated may present a safety hazard to a user, so that reliable operation of the user equipment 301 controlling the start of a safety critical test and potentially aborting the safety critical test is required.

[0048] Figure 4 shows an electrical tester 402 connected to a user equipment 401 by a Bluetooth or Bluetooth Low Energy communication link, in which a series of test messages 418 are transmitted from the electrical tester 402 and a response 419 to each test message is transmitted from the user equipment 401 as a check of the communication link. The communication link between the electrical tester 402 and the user equipment 401 is checked by sending a sequence of test messages, for example in the form of heartbeat messages 418 generated by a heartbeat generator function 416 in the processor 406 of the electrical tester, from the electrical tester 402 to the user equipment 401. A response 419 to each test message received is sent from the user equipment 401 to the electrical tester 402 and a heartbeat check function 417 generates an indication that the communication link has failed if a response is not received at the electrical tester 402 for a test message. A test is aborted by the processor 408 in response to the indication that the communication link has failed, providing a reliable indication that the communication link has failed so that the test can be stopped with a low false alarm rate and a high probability of detecting a link failure. The test messages in the sequence of test messages may be at regular intervals of time, so that the period of time that the communication link can fail without detection of the failure is limited. For example, the test messages may be sent with a spacing in time of less than one second and greater than half a second, typically 700 ms, which provides for efficient operation of the communication link while providing a sufficiently rapid response to a failure of the communication link to provide safe operation. Each test message comprises an identifier of the test message (shown in Figure 4 as “seq=N”, where N is a number in a numbered sequence) to distinguish the test message from other test messages in the sequence, and wherein each response comprises the identifier of the test message which caused the response. This method allows a reliable check that each test message has been successfully received in both directions of the link. Link failure can be detected if a response to any of the test messages is not received. As shown in Figure 4, the wireless transceiver in the electrical tester 402, in this example, is a Bluetooth or Bluetooth Low Energy module 407 and the wireless transceiver in user equipment 401, in this example, is also a Bluetooth or Bluetooth Low Energy module 405. The User equipment as a processor 406, on which an application level protocol 420 is implemented to receive the heartbeat messages 418 and to send responses 419 to the electrical tester.

[0049] In the embodiments described, several layers of safety are implemented, so that inadvertent dangerous operation is prevented. In the case of PAT testing three devices are present during the test:

[0050] 1) The Device Under Test (DUT) or appliance which might become energised or exposed to dangerous voltage. Note that the DUT can be faulty because it is the purpose of the test to detect any faults. Therefore, in this example, the danger does not come from the tester itself, but rather from the faulty DUT.

[0051] 2) The PAT tester (electrical tester) which provides the means of energising to dangerous levels.

[0052] 3) The remote controller in the form of user equipment having a mobile / tablet / computer application (APP).

[0053] After connecting DUT to PAT, the operator would interact with APP. Therefore, in case there is a problem with APP, the user would need to have some means of aborting the test in case something goes wrong, such as faulty appliance, or perhaps even faulty mobile phone on which the APP is running. To provide increased security there is a robust communication protocol between PAT and APP (over the wireless connection) which ensures that if everything operates correctly the user is always able to abort the critical test. In case of communication problems (flat battery, high noise affecting the wireless connection, frozen processor) the automatic handshaking between the two communicating units (PAT and APP) will automatically abort the test even without the intervention from the user.

[0054] During the remote operation, and specifically when a critical test is running, there is a regular “heartbeat” messaging (every 700 ms, or some other relatively short interval, for example in the range 500ms - 1000ms) that is generated by the PATs internal microcontroller (as shown in Figure 4). This heartbeat is passed onto the internal BT / BLE module and is transmitted wirelessly to the APP. The APP receives the heartbeat message and returns it via the same path to the PAT’s microcontroller. As long as the messages are passed through this loop then the critical test continues.

[0055] However, in case the APP stops responding then the heartbeat messages are no longer transmitted and the PAT instrument aborts the test automatically, as the loss of control is suspected.

[0056] An example of setup of the system is as follows:

[0057] 1. The APP is an application which, for example, runs on Android, iOS mobile devices and in Chrome and Edge browsers on Windows, or using any other web browser and operating system.

[0058] 2. The APP connects by Bluetooth to an instrument in order to control it remotely and receive information from it.

[0059] 3. Usually when one task has completed, the APP sends instructions to start the next task in the pre-defined sequence straightaway.

[0060] 4. Some instructions from the APP to the instrument can cause the instrument to perform a hazardous critical task.

[0061] 5. Before any such critical task is initiated, messages are choreographed between the APP and the instrument to ensure that sufficient safety measures are in place.

[0062] 6. Messages continue to be exchanged until the hazardous critical task has been completed.

[0063] An example of the heartbeat protocol implementation is as follows:

[0064] 1. The APP queries the instrument (electrical tester) to see if it is in a potentially hazardous (critical) state. In this particular implementation, the question is whether the instrument has mains voltage applied.

[0065] 2. If the next task is potentially hazardous (safety critical), the APP does not send the instruction to start the task straightaway. 3. Instead, it halts progress and puts up a 'Go' button next to the task, so the user must make a conscious action to start this task.

[0066] 4. Even after pressing 'Go' the user must confirm by moving a dot from left to right (for example) along a bar. This physical action prevents accidentally starting the test by inadvertently touching the device's touch screen or touch pad.

[0067] 5. When the dot reaches the end of the bar, the APP sends the instruction to start the task.

[0068] 6. At approximately the same time as starting the task (i.e. almost immediately after starting the task), the instrument sends the first of a regular heartbeat message to the APP. Each heartbeat for the task is uniquely numbered. In this particular implementation, the heartbeats are sent every 700 ms

[0069] 7. On receiving the heartbeat, the APP responds with an acknowledgement message. Each acknowledgement references the number of the specific heartbeat.

[0070] 8. If the instrument does not receive an acknowledgement by the time that the next heartbeat is due, the instrument aborts the task straightaway.

[0071] 9. If the instrument receives a timely acknowledgement to each heartbeat message, the task is allowed to run to completion.

[0072] 10. The heartbeats stop after the critical task has completed.

[0073] 11. The instrument proceeds to the next task in the sequence.

[0074] Figures 5A to 5F illustrate a sequence of displays on the user equipment showing the stages of starting a series of tests and aborting of a test under manual control or when a check of the communication link shows a link failure.

[0075] Figure 5A illustrates that a non-critical test can be started by pressing on the “play” button 501. This task is non-critical and therefore it is sufficient for the operator just to press on the “Go” button (“play” button) 501 for the test to be run. The user is prompted 502 to start the test by pressing Go. Once the test is completed then a “tick” is shown next to it, as shown in Fig 5B. If the test fials to be completed, a “cross” is shown. Execution of a critical task undergoes several stages. In phase 1, as shown in Figure 5B, the user is informed 504 that a safety critical task is about to be performed, and that the user needs to press the “Go” button 503.

[0076] After pressing the Go button the APP moves to phase 2, as shown in Figure 5C, in which the user is informed 505 that the sliding action is necessary for starting the safety critical test. A track appears, in this case linear, along which a slider, which may be a dot 506, may be moved. The track may have a non-linear shape, for example involving movement in two dimensions, such as along a curve, in other examples.

[0077] In phase 3, as shown in Figure 5D, the user needs to slide the “dot” 508 from a start to the end position, as dictated by the messaging and graphics 507 presented in the user interface.

[0078] In phase 4, as shown in Figure 5E, all the actions from the operators were satisfied and the critical test is commenced by the electrical tester, and the test is running, as indicated by the display 510. A manual abort button 509 is provided.

[0079] In phase 5 (not shown) the test may finish correctly and generate a display similar to the display shown in Figure 5B for the non-critical test.

[0080] However, the user may choose to abort the critical test (or in some examples also a non-critical test). With the communications (such as heartbeat) running correctly then appropriate functionality such as the “Stop” button 509 is available during the test (as shown in Figure 5E). After the test is aborted an appropriate message 511 is displayed on the APP interface (as shown in Figure 5F). If a communications link failure is detected, the display may also show an indication 511 that the test has been aborted.

[0081] As illustrated, a series of tests is performed of the device under test under control of the user equipment, the series comprising a non-safety-critical test and a safety critical test. The user equipment is configured to cause the electrical equipment to perform the non-safety-critical test without requiring the user interaction, which may be a two-stage interaction, that is required for the safety- critical test. This method allows for efficient operation of the measurement equipment by allowing a less onerous procedure for starting a non-safety-critical test, and reducing the chance that the user becomes accustomed to performing the interaction for starting the safety-critical test and thereby becomes more likely to perform the interaction inadvertently.

[0082] Figure 6 is a flow diagram of a method of operating the measurement apparatus as described herein according to steps S6.1 to S6.4 and Figure 7 is a flow diagram of a further method of operating the measurement apparatus as described herein according to steps S7.1 to S7.4.

[0083] The above embodiments are to be understood as illustrative examples of the invention. It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.

Claims

CLAIMS1. A method of operation of measurement apparatus for performing a test of an electrical parameter of a device under test, the test comprising providing a voltage to the device under test, the measurement apparatus comprising an electrical tester for connection to the device under test and user equipment configured to control the electrical tester using a communication link, the method comprising: configuring the user equipment to be capable of causing the electrical tester to start a first test in response to a first user interaction with the user equipment; starting the first test in response to the first user interaction; checking the communication link while the first test is in progress; and aborting the first test if a check of the communication link indicates that the communication link has failed, wherein aborting the first test comprises, without user intervention, stopping providing the voltage to the device under test.

2. A method according to claim 1, comprising: checking the communication link by sending a sequence of test messages from the electrical tester to the user equipment, sending a response to each test message received at the user equipment from the user equipment to the electrical tester and generating an indication that the communication link has failed if a response is not received at the electrical tester for a test message; and aborting the first test in response to the indication that the communication link has failed.

3. A method according to claim 2, comprising sending the test messages in the sequence of test messages at regular intervals of time.

4. A method according to claim 3, comprising sending the test messages with a spacing in time of less than one second and greater than half a second.

5. A method according to any one of claim 2 to claim 4, wherein each test message comprises an identifier of the test message to distinguish the test message from other test messages in the sequence, and wherein each response comprises the identifier of the test message which caused the response.

6. A method according to any preceding claim, wherein the first user interaction comprises two separate actions of the user in interaction with a touch sensitive screen.

7. A method according to claim 6, wherein the first user interaction comprises a user touching a predefined part of the touch sensitive screen, and then touching the screen to move a slider across the screen.

8. A method according to claim 7, wherein the first user interaction comprises moving the slider to follow a track having a non-linear shape.

9. A method according to any preceding claim, wherein the first test is a safety critical test.

10. A method according to claim 9, wherein the voltage provided to the device under test is a mains voltage and the device under test is energised by the mains voltage.

11. A method according to claim 10, wherein the voltage provided to the device is applied to a mains socket on the electrical tester to power the device under test.

12. A method according to claim 10 or claim 11, wherein powering the device under test causes a risk to an operator of the measurement apparatus and the user equipment is configured to generate a warning that the appliance may operate before allowing said first user interaction with the user equipment.

13. A method according to claim 9, wherein device under test is an insulator, and the electrical tester provides a hazardous live output to test leads for connection to the insulator.

14. A method according to any preceding claim, comprising performing a series of tests of the device under test under control of the user equipment, wherein the series of tests comprises the first test as a safety critical test and a non-safety-critical test, wherein the user equipment is configured to cause the electrical equipment to perform the non-safety-critical test without requiring the first user interaction.

15. A method according to any preceding claim, comprising configuring the user equipment to be capable of causing the electrical tester to be capable of causing an abortion of the first test while the first test is in progress in response to a second user interaction with the user equipment.

16. A method according to any preceding claim, wherein the second user interaction comprises touching a second predefined part of a touch sensitive screen.

17. An electrical tester for use in measurement apparatus for performing a test of an electrical parameter of a device under test, the test comprising providing a voltage to the device under test, the measurement apparatus comprising the electrical tester for connection to the device under test and user equipment configured to control the electrical tester using a communication link, the electrical tester comprising:a voltage interrupter controllable to prevent the electrical tester from providing the voltage to the device under test; a wireless transceiver configured to provide the communication link with the user equipment; and one or more processors configured to: start a first test in response to an indication from the user equipment of a first user interaction with the user equipment; and check the communication link and abort the test, by causing the voltage interrupter to prevent the electrical tester from providing the voltage to the device under test in response to a communication link failure.

18. An electrical tester according to claim 17, wherein the voltage interrupter comprises one or more relays.

19. An electrical tester according to claim 17 or claim 18, wherein the voltage interrupter is configured for connection to an external power source.

20. An electrical tester according to any one of claims 17 to 19, wherein the voltage provided to the device under test is a mains voltage and the device under test is energised by the mains voltage.

21. An electrical tester according to claim 20, comprising a mains socket, wherein the voltage provided to the device is applied to the mains socket on the electrical tester to power the device under test.

22. An electrical tester according to any one of claims 17 to 21, wherein the voltage interrupter is implemented by functions of a voltage generator that may be switched on or off.

23. A system comprising an electrical tester according to any one of claims 17 to 22 and user equipment configured as a remote control adapted to receive and respond to a communication link test signal generated by the electrical tester.

24. The system of claim 23, configured to perform the method of any one of claims 1 to 16.

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