Automatic leakage current testing device of proximity switch

Abstract

The utility model provides a leakage current automatic testing device of a proximity switch, and relates to the field of proximity switch testing. The tested device is connected with a power supply positive electrode and a power supply negative electrode of the power supply; and the testing device is connected with the switch output of the tested device and is connected with the power supply. The utility model provides an automatic leakage current testing device for a proximity switch, and solves the problem that a digital potentiometer cannot be directly used for replacing a power load resistor for testing.

Description

Technical Field

[0001] The utility model relates to the field of proximity switch testing, in particular to an automatic leakage current testing device for a proximity switch. Background Art

[0002] A proximity switch is a position switch that can be triggered without direct contact with moving parts. When an object approaches the sensing surface of the switch to the action distance, the switch can be activated without mechanical contact or any pressure, thereby driving DC appliances or providing control instructions to computer devices.

[0003] The existing technologies are all manual tests. During manual testing, a sliding rheostat is used for testing, and there is no automatic testing solution. During leakage current testing, normal devices measure low voltage and small current, and cannot be measured using an electronic load. Abnormal devices measure high voltage and large current, so a digital potentiometer cannot be used directly to replace the power load resistor for testing. Utility Model Content

[0004] The utility model provides an automatic leakage current testing device for a proximity switch, which solves the problem that a digital potentiometer cannot be used directly to replace a power load resistor for testing.

[0005] In order to solve the above technical problems, the technical solution of the utility model is as follows:

[0006] The embodiment of the utility model provides a leakage current automatic testing device for a proximity switch, comprising:

[0007] Device under test;

[0008] A power supply, the device under test is connected to the positive power supply and the negative power supply of the power supply;

[0009] A testing device is connected to the switch output of the device under test and to the power supply.

[0010] Furthermore, the testing device comprises:

[0011] MOSFET device M1, connected to the switch output and the negative electrode of the power supply;

[0012] A digital potentiometer U5 connected to the MOSFET device M1;

[0013] A current-voltage conversion circuit connected to the negative electrode of the power supply and the digital potentiometer U5;

[0014] An inverting amplifier circuit connected to the current-voltage conversion circuit;

[0015] A filter buffer circuit connected to the inverting amplifier circuit;

[0016] A microcontroller connected to the digital potentiometer U5, the current-voltage conversion circuit and the filter buffer circuit;

[0017] The voltage-controlled current source circuit is connected to the microcontroller.

[0018] Furthermore, the current-to-voltage conversion circuit includes:

[0019] The internal operational amplifier U2, the non-inverting input terminal is connected to the negative pole of the power supply and is also connected to the ground wire;

[0020] A diode D1, whose anode is connected to the inverting input terminal of the internal operational amplifier U2, and whose cathode is connected to the non-inverting input terminal of the internal operational amplifier U2;

[0021] A diode D2, an anode of which is connected to the non-inverting input terminal of the internal operational amplifier U2, and a cathode of which is connected to the inverting input terminal of the internal operational amplifier U2;

[0022] A diode D3, a cathode of which is connected to the output terminal of the internal operational amplifier U2;

[0023] A capacitor C2 is connected in parallel with the internal operational amplifier U2;

[0024] A resistor R5, one end of which is connected to the inverting input terminal of the internal operational amplifier U2, and the other end of which is connected to the digital potentiometer U5;

[0025] A resistor R7 connected in parallel with the internal operational amplifier U2, the diode D3 and the resistor R5;

[0026] A resistor R8 is connected in series with the switch K2, and the resistor R8, the switch K2 and the resistor R7 are connected in parallel;

[0027] Capacitor C4, connected in parallel with resistor R8;

[0028] Capacitor C3 is connected in parallel with resistor R8 and switch K2.

[0029] Furthermore, the inverting amplifier circuit comprises:

[0030] A resistor R3 is connected to the anode of the diode D3;

[0031] An internal operational amplifier U1, an inverting input terminal is connected to the resistor R3, and a non-inverting input terminal is connected to the ground line;

[0032] A resistor R4 is connected in parallel with the internal operational amplifier U1;

[0033] One end of the resistor R2 is connected to the output end of the internal operational amplifier U1, and the other end is connected to the ground.

[0034] Furthermore, the filtering buffer circuit includes:

[0035] Resistor R6, connected to the inverting amplifier circuit;

[0036] A capacitor C1, one end of which is connected to the resistor R6, and the other end of which is connected to the ground wire;

[0037] The internal operational amplifier U3 has a non-inverting input terminal connected to the resistor R6 and an inverting input terminal connected to the output terminal.

[0038] Furthermore, the voltage-controlled current source circuit includes:

[0039] A switch K1 connected to the MOSFET device M1;

[0040] A resistor R14 connected to the switch K1;

[0041] An internal operational amplifier U6, the output end of which is connected to the resistor R14;

[0042] A resistor R10, one end of which is connected to the output end of the internal operational amplifier U6, and the other end of which is connected to the inverting input end of the internal operational amplifier U6;

[0043] A resistor R1, one end of which is connected to the inverting input terminal of the internal operational amplifier U6, and the other end of which is connected to the ground line;

[0044] An internal operational amplifier U4, a non-inverting input terminal connected to the resistor R14, and an inverting input terminal connected to the output terminal;

[0045] A resistor R13, one end of which is connected to the output end of the internal operational amplifier U4, and the other end of which is connected to the non-inverting input end of the internal operational amplifier U6;

[0046] The resistor R12 has one end connected to the resistor R13 and the other end connected to the microcontroller.

[0047] Further, the microcontroller is connected to the switch K1;

[0048] The microcontroller is connected to the switch K2.

[0049] Further, the microcontroller is connected to a first isolated communication, a second isolated communication and a third isolated communication;

[0050] The first isolated communication is connected to the resistor R12 via a first digital-to-analog converter;

[0051] The second isolated communication is connected to the internal operational amplifier U3 via a second digital-to-analog converter;

[0052] The third isolated communication is connected to the digital potentiometer U5.

[0053] Furthermore, the device under test includes an NPN proximity switch and a PNP proximity switch.

[0054] The above solution of the utility model includes at least the following beneficial effects:

[0055] The automatic leakage current testing device of the proximity switch described in the utility model uses a depletion-type MOSFET for current limiting protection to prevent damage to the digital potentiometer when the proximity switch or proximity sensor is triggered by mistake, thereby solving the problem that the digital potentiometer cannot directly replace the load resistor; a current-to-voltage conversion circuit is adopted, and the virtual ground function of the operational amplifier circuit is utilized to convert the input current into a test voltage to ensure load accuracy and improve measurement progress; a current source calibration circuit is added, and a calibrated current source can be used to calibrate and self-check the measurement part circuit, thereby facilitating automated testing. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 The utility model is a circuit diagram of an automatic leakage current testing device for a proximity switch.

[0057] Description of reference numerals:

[0058] 1. Device under test; 2. Power supply; 3. Test device; 31. MOSFET device M1; 32. Digital potentiometer U5; 33. Current-voltage conversion circuit; 34. Inverting amplifier circuit; 35. Filter buffer circuit; 36. Microcontroller; 37. Voltage-controlled current source circuit; 361. First isolated communication; 362. Second isolated communication; 363. Third isolated communication; 364. First digital-to-analog converter; 365. Second digital-to-analog converter. DETAILED DESCRIPTION

[0059] The exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0060] like Figure 1 As shown, an embodiment of the utility model provides an automatic leakage current testing device for a proximity switch, comprising:

[0061] Device under test 1;

[0062] A power supply 2, wherein the device under test 1 is connected to a positive power supply electrode and a negative power supply electrode of the power supply 2;

[0063] The testing device 3 is connected to the switch output of the device under test 1 and to the power supply 2 .

[0064] In the embodiment of the utility model, the device under test 1 is a three-wire proximity switch or proximity sensor. By connecting the power supply 2 and the test device 3, both NPN and PNP proximity switches or proximity sensors can be tested. During the leakage current test, the device under test is powered but the switch is not triggered. The leakage current of the switch output to the negative pole of the PNP power supply or the positive pole of the NPN power supply is measured. By measuring the leakage current, the normal working state of the device can be judged and potential fault problems can be discovered in advance.

[0065] like Figure 1 As shown, the testing device 3 comprises:

[0066] MOSFET device M131, connected to the switch output and the negative electrode of the power supply;

[0067] A digital potentiometer U532 is connected to the MOSFET device M1;

[0068] A current-voltage conversion circuit 33 is connected to the negative electrode of the power supply and the digital potentiometer U532;

[0069] An inverting amplifier circuit 34 connected to the current-voltage conversion circuit 33;

[0070] A filter buffer circuit 35 connected to the inverting amplifier circuit 34;

[0071] A microcontroller 36 connected to the digital potentiometer U532, the current-voltage conversion circuit 33 and the filter buffer circuit 35;

[0072] The voltage-controlled current source circuit 37 is connected to the microcontroller 36 .

[0073] In the embodiment of the utility model, a depletion type N-type MOSFET device M1 is used to implement overcurrent protection. When the current is large, M1 will automatically cut off. The on-resistance of M1 is very small, generally less than 10 ohms, and can be used as a part of the load to prevent the digital potentiometer from being damaged when the proximity switch or proximity sensor is triggered by mistake. The problem that the digital potentiometer cannot directly replace the load resistor is solved, because the device under test may be defective. If there is no current limiting protection, the digital potentiometer U5 will be damaged under high current impact; the digital potentiometer U5 adopts multi-channel parallel connection to improve the resolution of the digital potentiometer and increase the working current of the digital potentiometer; the current-voltage conversion circuit 3 is adopted 3. The virtual ground function of the operational amplifier circuit is used to convert the input current into a test voltage to ensure the accuracy of the load and improve the measurement progress; the inverting amplifier circuit 34 amplifies the voltage signal output by the current-voltage conversion circuit; the filter buffer circuit 35 filters and buffers the amplified voltage signal to reduce noise and interference; the microcontroller 36 is connected to the digital potentiometer U5, the current-voltage conversion circuit and the filter buffer circuit to control the working state of the test device and collect and process the leakage current data; the voltage-controlled current source circuit 37 is connected to the microcontroller, and the calibrated current source can calibrate and self-check the measurement part circuit to facilitate automated testing.

[0074] like Figure 1 As shown, the current-to-voltage conversion circuit 33 includes:

[0075] The internal operational amplifier U2, the non-inverting input terminal is connected to the negative pole of the power supply and is also connected to the ground wire;

[0076] A diode D1, whose anode is connected to the inverting input terminal of the internal operational amplifier U2, and whose cathode is connected to the non-inverting input terminal of the internal operational amplifier U2;

[0077] A diode D2, an anode of which is connected to the non-inverting input terminal of the internal operational amplifier U2, and a cathode of which is connected to the inverting input terminal of the internal operational amplifier U2;

[0078] A diode D3, a cathode of which is connected to the output terminal of the internal operational amplifier U2;

[0079] A capacitor C2 is connected in parallel with the internal operational amplifier U2;

[0080] A resistor R5, one end of which is connected to the inverting input terminal of the internal operational amplifier U2, and the other end of which is connected to the digital potentiometer U5;

[0081] A resistor R7 connected in parallel with the internal operational amplifier U2, the diode D3 and the resistor R5;

[0082] A resistor R8 is connected in series with the switch K2, and the resistor R8, the switch K2 and the resistor R7 are connected in parallel;

[0083] Capacitor C4, connected in parallel with resistor R8;

[0084] Capacitor C3 is connected in parallel with resistor R8 and switch K2.

[0085] In the embodiment of the utility model, the digital potentiometer U5 is used as a load, and the current flowing through the digital potentiometer U5 is measured by a current-voltage conversion circuit 33; the current-voltage conversion circuit 33 is used to amplify the current signal using the operational amplifier U2, and the principle of negative feedback is used to make the input current zero (virtual disconnection) and the differential input voltage zero (virtual short), so that the voltage at the lower end of U5 is equal to the voltage at the reference ground point, ensuring that the test requirements are met; wherein R5, D1, and D2 are used to prevent the current flowing through the digital potentiometer U5 from exceeding the range of U5 when the resistance value set is small, so as to further protect U5 from damage; the diode D3 is used to convert the amplified current signal into a voltage signal; the capacitor C2 is used to connect the digital potentiometer U5 to the digital potentiometer U5, and the current flowing through the digital potentiometer U5 is connected to the digital potentiometer U5 ...; the diode D3 is used to convert the amplified current signal into a voltage signal; the capacitor C2 is used to connect the digital potentiometer U5 to the digital potentiometer U5, and the current flowing through the digital potentiometer U5 is connected to the digital potentiometer U5 to prevent the current flowing through the digital potentiometer U5 from exceeding the range of U5 when the resistance value set is small; the capacitor C2 is used to connect the digital potentiometer U5 to the digital potentiometer U5, and the current flowing through the digital potentiometer U5 is connected The feedback loop of the internal operational amplifier U2 plays a role in stabilizing the operation of the amplifier, thereby improving the stability and accuracy of the circuit; the resistor R5 is used to adjust the gain of the current-voltage conversion circuit to adapt to different current ranges and test requirements; the resistor R7 is connected in parallel with the diode D3 and the resistor R5 to adjust the bias of the output voltage; the resistor R8 and the switch K2 are used to control the range of current-voltage conversion so that the measured voltage range can adapt to different test requirements; the capacitors C3 and C4 are used for filtering and removing interference to improve the stability and accuracy of the measurement results; the current-voltage conversion circuit 33 can effectively realize the conversion of current to voltage and provide accurate and reliable signals for subsequent measurements.

[0086] like Figure 1 As shown, the inverting amplifier circuit 34 includes:

[0087] A resistor R3 is connected to the anode of the diode D3;

[0088] An internal operational amplifier U1, an inverting input terminal is connected to the resistor R3, and a non-inverting input terminal is connected to the ground line;

[0089] A resistor R4 is connected in parallel with the internal operational amplifier U1;

[0090] One end of the resistor R2 is connected to the output end of the internal operational amplifier U1, and the other end is connected to the ground.

[0091] In the embodiment of the utility model, U1, R3, R4, and R2 constitute an inverting amplifier circuit 34, which amplifies or reduces the voltage value of the current-voltage conversion and outputs it to the subsequent circuit or device; the resistor R3 is used to limit the current flowing through the diode D3 to ensure the stable working state of the positive electrode of the diode; the internal operational amplifier U1 is the core component of the inverting amplifier circuit, and the input signal is introduced through the resistor R3 at the inverting input end, and the amplified signal is output through the output end; the resistor R4 is connected in parallel with the internal operational amplifier U1, and is used to adjust the gain of the amplifier circuit to adapt to different signal amplification requirements; the resistor R2 connects the output signal to the ground wire, which is used to determine the reference point of the inverting amplifier to ensure the accuracy and stability of the output signal.

[0092] like Figure 1 As shown, the filtering buffer circuit 35 includes:

[0093] Resistor R6, connected to the inverting amplifier circuit 34;

[0094] A capacitor C1, one end of which is connected to the resistor R6, and the other end of which is connected to the ground wire;

[0095] The internal operational amplifier U3 has a non-inverting input terminal connected to the resistor R6 and an inverting input terminal connected to the output terminal.

[0096] In the embodiment of the utility model, R6, C1, and U3 constitute a filter buffer circuit 35, which filters and buffers the amplified signal, and transmits the final measured voltage value to the microcontroller 36 to improve the signal quality and stability; the resistor R6 is used to connect the inverting amplifier circuit 34 and the filter buffer circuit 35, and inputs the amplified signal into the filter buffer circuit 35; the capacitor C1 is connected in parallel with the resistor R6 to play a filtering role and remove high-frequency noise and interference in the input signal; the internal operational amplifier U3 is used to amplify the filtered signal, increase the amplitude and power of the signal, and is connected to the resistor R6 through the non-phase input terminal, and the inverting input terminal is connected to the output terminal to filter and buffer the signal, providing a clean and stable output signal to meet subsequent measurement and processing requirements.

[0097] like Figure 1 As shown, the voltage-controlled current source circuit 37 includes:

[0098] A switch K1 connected to the MOSFET device M1;

[0099] A resistor R14 connected to the switch K1;

[0100] An internal operational amplifier U6, the output end of which is connected to the resistor R14;

[0101] A resistor R10, one end of which is connected to the output end of the internal operational amplifier U6, and the other end of which is connected to the inverting input end of the internal operational amplifier U6;

[0102] A resistor R1, one end of which is connected to the inverting input terminal of the internal operational amplifier U6, and the other end of which is connected to the ground wire;

[0103] An internal operational amplifier U4, a non-inverting input terminal connected to the resistor R14, and an inverting input terminal connected to the output terminal;

[0104] A resistor R13, one end of which is connected to the output end of the internal operational amplifier U4, and the other end of which is connected to the non-inverting input end of the internal operational amplifier U6;

[0105] The resistor R12 has one end connected to the resistor R13 and the other end connected to the microcontroller 36 .

[0106] In the embodiment of the utility model, K1, U4, U6, R1, R10, R12, R13, and R14 constitute a voltage-controlled current source circuit 37 for calibration, and the microcontroller outputs the current value. When the device under test is not connected, the calibration function is realized to ensure the accuracy of the measurement circuit; the switch K1 is used to control the on-off state of the MOSFET device M1, thereby controlling the power supply voltage of the device under test; the resistor R14 is connected to the switch K1 and is used to connect to the internal operational amplifier U6 and the internal operational amplifier U4; the internal operational amplifier U6 controls the MOSFET device M1 through the output terminal and the resistor R14. 1, thereby controlling the supply voltage of the device under test; resistors R10 and R1 are connected to the internal operational amplifier U6, and are used to adjust the amplification factor and gain of the internal operational amplifier U6; the internal operational amplifier U4 is connected to the MOSFET device M1 through the non-phase input terminal and the resistor R14, and is used to control the supply voltage of the device under test; the resistor R13 is connected to the internal operational amplifier U4 and the internal operational amplifier U6, and is used to transmit the control signal and adjust the working state of the current source circuit; the resistor R12 is connected to the resistor R13 and is connected to the microcontroller, and is used to control the working state of the current source circuit.

[0107] like Figure 1 As shown, the microcontroller 36 is connected to the switch K1;

[0108] The microcontroller 36 is connected to the switch K2 .

[0109] In the embodiment of the utility model, the microcontroller 36 is connected to the switch K1 and is used to control the on-off state of the switch K1, thereby controlling the on-and-off states of the MOSFET device M1 and the voltage-controlled current source circuit 37. The microcontroller can control the on-and-off state of the switch K1 as needed, thereby controlling the power supply voltage of the device under test; the microcontroller is connected to the switch K2 and is used to control the on-and-off state of the switch K2, thereby controlling the range of the current-voltage conversion circuit.

[0110] like Figure 1 As shown, the microcontroller 36 is connected to a first isolated communication 361, a second isolated communication 362 and a third isolated communication 363;

[0111] The first isolated communication 361 is connected to the resistor R12 via a first digital-to-analog converter 364;

[0112] The second isolated communication 362 is connected to the internal operational amplifier U3 via a second digital-to-analog converter 365;

[0113] The third isolated communication 363 is connected to the digital potentiometer U52.

[0114] In an embodiment of the utility model, the first isolated communication 361 is connected to the resistor R12 through the first digital-to-analog converter 364, and the voltage-controlled current source circuit 37 is controlled by the microcontroller 36 to convert the output voltage of the first digital-to-analog converter 364 into a current value; the second isolated communication 362 is connected to the internal operational amplifier U3 through the second digital-to-analog converter 365, and the filter buffer circuit 35 transmits the final measured voltage value to the second digital-to-analog converter 365, and the microcontroller 36 reads the voltage value and then calculates the current value; the third isolated communication 363 is connected to the digital potentiometer U52 to control and read U5; the microcontroller 36 uses isolated communication to isolate the input signal from the output signal, avoid signal interference and mutual influence, improve the stability and reliability of the system, and reduce errors caused by signal interference; isolated communication can improve the safety of the system, avoid the harm of high voltage, high current, etc. to the microcontroller and external equipment, and reduce the possibility of accidents.

[0115] Optionally, the internal operational amplifiers U1, U2, U3, U4, and U6 are powered by an isolated power supply, which can achieve electrical isolation between the internal operational amplifiers and the external circuit, and can effectively prevent factors such as noise and interference in the external circuit from being transmitted to the internal operational amplifiers, thereby ensuring the stability and reliability of the internal circuit; it can avoid the influence of ground interference on the internal operational amplifiers and improve the anti-interference ability of the system; the isolated power supply can protect the internal operational amplifiers from external dangerous factors such as high voltage and high current, improve the safety of the system, and can effectively prevent damage to the internal operational amplifiers due to power overload, voltage mutation, etc.

[0116] In the embodiment of the utility model, the measurement result of the digital potentiometer U5 is compared with the manual test solution test data error within 1%, which meets the customer's test requirements; the current limiting protection circuit of the actual test can effectively protect the digital potentiometer U5 in the case of false triggering; the use of isolated power supply and isolated communication mode can cover the DC range of 0 to 60V, covering the measurement range of most three-wire proximity switches or proximity sensors; the use of current-voltage conversion circuit solves the problem of small input voltage range during leakage current testing and low measurement accuracy using an ammeter.

[0117] The above is a preferred embodiment of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. An automatic leakage current testing device for a proximity switch, characterized in that: include: Device under test (1); A power supply (2), the device under test (1) being connected to a positive power supply electrode and a negative power supply electrode of the power supply (2); A testing device (3) is connected to the switch output of the device under test (1) and to the power supply (2).

2. The automatic leakage current testing device for a proximity switch according to claim 1, characterized in that: The testing device (3) comprises: MOSFET device M1 (31), connected to the switch output and the negative electrode of the power supply; A digital potentiometer U5 (32), connected to the MOSFET device M1; A current-voltage conversion circuit (33) connected to the negative electrode of the power supply and the digital potentiometer U5 (32); An inverting amplifier circuit (34) connected to the current-voltage conversion circuit (33); A filter buffer circuit (35) connected to the inverting amplifier circuit (34); A microcontroller (36) connected to the digital potentiometer U5 (32), the current-voltage conversion circuit (33) and the filter buffer circuit (35); A voltage-controlled current source circuit (37) is connected to the microcontroller (36).

3. The automatic leakage current testing device for a proximity switch according to claim 2, characterized in that: The current-voltage conversion circuit (33) comprises: The internal operational amplifier U2, the non-inverting input terminal is connected to the negative pole of the power supply and is also connected to the ground wire; A diode D1, whose anode is connected to the inverting input terminal of the internal operational amplifier U2, and whose cathode is connected to the non-inverting input terminal of the internal operational amplifier U2; A diode D2, an anode of which is connected to the non-inverting input terminal of the internal operational amplifier U2, and a cathode of which is connected to the inverting input terminal of the internal operational amplifier U2; A diode D3, a cathode of which is connected to the output terminal of the internal operational amplifier U2; A capacitor C2 is connected in parallel with the internal operational amplifier U2; A resistor R5, one end of which is connected to the inverting input terminal of the internal operational amplifier U2, and the other end of which is connected to the digital potentiometer U5; A resistor R7 connected in parallel with the internal operational amplifier U2, the diode D3 and the resistor R5; A resistor R8 is connected in series with the switch K2, and the resistor R8, the switch K2 and the resistor R7 are connected in parallel; Capacitor C4, connected in parallel with resistor R8; Capacitor C3 is connected in parallel with resistor R8 and switch K2.

4. The automatic leakage current testing device for a proximity switch according to claim 3, characterized in that: The inverting amplifier circuit (34) comprises: A resistor R3 is connected to the anode of the diode D3; An internal operational amplifier U1, an inverting input terminal is connected to the resistor R3, and a non-inverting input terminal is connected to the ground line; A resistor R4 is connected in parallel with the internal operational amplifier U1; One end of the resistor R2 is connected to the output end of the internal operational amplifier U1, and the other end is connected to the ground.

5. The automatic leakage current testing device for a proximity switch according to claim 4, characterized in that: The filter buffer circuit (35) comprises: A resistor R6 connected to the inverting amplifier circuit (34); A capacitor C1, one end of which is connected to the resistor R6, and the other end of which is connected to the ground wire; The internal operational amplifier U3 has a non-inverting input terminal connected to the resistor R6 and an inverting input terminal connected to the output terminal.

6. The automatic leakage current testing device for a proximity switch according to claim 5, characterized in that: The voltage-controlled current source circuit (37) comprises: A switch K1 connected to the MOSFET device M1 (31); A resistor R14 connected to the switch K1; An internal operational amplifier U6, the output end of which is connected to the resistor R14; A resistor R10, one end of which is connected to the output end of the internal operational amplifier U6, and the other end of which is connected to the inverting input end of the internal operational amplifier U6; A resistor R1, one end of which is connected to the inverting input terminal of the internal operational amplifier U6, and the other end of which is connected to the ground wire; An internal operational amplifier U4, a non-inverting input terminal connected to the resistor R14, and an inverting input terminal connected to the output terminal; A resistor R13, one end of which is connected to the output end of the internal operational amplifier U4, and the other end of which is connected to the non-inverting input end of the internal operational amplifier U6; The resistor R12 has one end connected to the resistor R13 and the other end connected to the microcontroller (36).

7. The automatic leakage current testing device for a proximity switch according to claim 6, characterized in that: The microcontroller (36) is connected to the switch K1; The microcontroller (36) is connected to the switch K2.

8. The automatic leakage current testing device for a proximity switch according to claim 7, characterized in that: The microcontroller (36) is connected to a first isolated communication (361), a second isolated communication (362) and a third isolated communication (363); The first isolated communication (361) is connected to the resistor R12 via a first digital-to-analog converter (364); The second isolated communication (362) is connected to the internal operational amplifier U3 via a second digital-to-analog converter (365); The third isolated communication (363) is connected to the digital potentiometer U5 (32).

9. The automatic leakage current testing device for a proximity switch according to claim 8, characterized in that: The device under test (1) comprises an NPN type proximity switch and a PNP type proximity switch.

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