An online assessment system for pointer multimeter

Abstract

The present invention discloses an online assessment system for a pointer multimeter, which belongs to the field of electrician training, including a teacher's end and several assessment ends, and the several assessment ends are wirelessly connected to the teacher's end. The assessment end includes a multimeter, a test pen, a multimeter detection protection device, a mobile phone and a test terminal. The test pen is connected to the multimeter via the multimeter detection protection device, and the test head of the test pen is connected to the test terminal. The test terminal is wirelessly connected to the teacher's end via the mobile phone. By setting a test terminal to replace the electrician's electrician box, the teacher's end inputs the assessment parameters, which are transmitted to the test terminal through wireless, and then displayed to the student to use the multimeter for testing. Then the multimeter detection protection device monitors whether the gear position played by the student is correct, and realizes remote automatic deduction of points. At the same time, after the student is measured, the measurement result is input into the test terminal, and then transmitted back to the teacher's end, so as to realize the remote multimeter assessment and scoring record, and solve the problem of online class electrician training assessment under the epidemic situation.

Description

Technical Field

[0001] The invention relates to the field of electronic technology, and in particular to an online assessment system for a pointer multimeter. Background Art

[0002] In the existing electrician training or electrician certification, the multimeter assessment among the three meters is relatively time-consuming. The examiner has to watch the student's meter position in real time to see if it is correct, and then give the student a score. This assessment method is very labor-intensive, and the teacher or examiner will be very tired after a whole day. Therefore, it is necessary to design a device that can replace manual multimeter assessment.

[0003] Especially in the context of the epidemic, many courses have chosen to be taught online. However, for practical electrician training, after the theory is taught online, actual operation training is required for assessment. Therefore, it is necessary to design an online electrician assessment device. Summary of the invention

[0004] The purpose of the present invention is to provide an online assessment system for a pointer multimeter, so as to solve the technical problems that the existing multimeter can only be checked by the examiner, the work intensity is high, and remote online assessment is impossible.

[0005] A pointer multimeter online assessment system comprises a teacher end and several assessment ends, wherein the several assessment ends are wirelessly connected to the teacher end, the assessment end comprises a multimeter, a test lead, a multimeter detection protection device, a mobile phone and a test terminal, the test lead is connected to the multimeter via the multimeter detection protection device, the test head of the test lead is connected to the test terminal, and the test terminal is wirelessly connected to the teacher end via the mobile phone.

[0006] Furthermore, the multimeter detection and protection device includes a front shell of the detection and protection device, a rear shell of the detection and protection device, a multimeter connection terminal and a test pen socket. The front shell of the detection and protection device and the rear shell of the detection and protection device are arranged to cover each other, and a multimeter detection and protection circuit is arranged inside. The multimeter connection terminal is arranged on the side of the front shell of the detection and protection device and is connected to the test pen of the multimeter. The test pen socket is arranged at the front end of the front shell of the detection and protection device and is connected to the test pen. The multimeter detection and protection circuit is connected to the multimeter connection terminal and the test pen socket.

[0007] Furthermore, the test terminal includes a test terminal front shell, a test terminal rear shell, a test terminal power adapter socket, a test terminal test terminal, a test terminal matrix keyboard, a test terminal voice outlet and a test terminal TFT color screen. The test terminal front shell and the test terminal rear shell are arranged to cover each other, and a test circuit is arranged inside. The test terminal power adapter socket is arranged on the side of the test terminal front shell, and the test terminal test terminal, the test terminal matrix keyboard, the test terminal voice outlet and the test terminal TFT color screen are arranged at the front end of the test terminal front shell. The test terminal power adapter socket, the test terminal test terminal, the test terminal matrix keyboard, the test terminal voice outlet and the test terminal TFT color screen are all connected to the test circuit.

[0008] Furthermore, the multimeter detection protection circuit includes a switching protection circuit, a detection controller circuit, a gear detection circuit and a detection Bluetooth wireless transceiver module. The switching protection circuit, the gear detection circuit and the detection Bluetooth wireless transceiver module are all connected to the detection controller circuit, the detection end of the gear detection circuit is connected to the input end of the switching protection circuit, the input end of the switching protection circuit is connected to the multimeter, and the output end of the switching protection circuit is connected to the test terminal.

[0009] Furthermore, the gear detection circuit includes a voltage sampling circuit and a resistance sampling circuit, the output end of the voltage sampling circuit is connected to the detection controller circuit, and the sampling end of the voltage sampling circuit is respectively connected to the output end of the resistance sampling circuit and the input end of the switching protection circuit.

[0010] Furthermore, the resistance sampling circuit includes resistors R1-R12, an electronic switch I, an electronic switch II and an amplifier A1, one end of the resistor R1 is connected to a +5V power supply, resistors R1-R5 are connected in series, the four switch input ends of the electronic switch I are respectively connected between the resistor R1 and the resistor R2, between the resistor R2 and the resistor R3, between the resistor R3 and the resistor R4, and between the resistor R4 and the resistor R5, the bus end of the electronic switch I is connected to an input end of the switching protection circuit, the other input end of the switching protection circuit is connected to the bus end of the electronic switch II and the positive input end of the amplifier A1, one end of the resistor R6 is grounded, and the other end is connected to the negative input end of the amplifier A1, one end of the resistors R7-R12 are respectively connected to the six switch pins of the sub-switch II, and the other ends are all connected to the output end of the amplifier A1, and the sampling end of the voltage sampling circuit is connected to the output end of the amplifier A1.

[0011] Furthermore, the test circuit includes a test Bluetooth wireless transceiver module, a voice broadcast module, a test end controller circuit, a TFT color display circuit, a matrix keyboard circuit, a voltage parameter generating circuit, a current parameter generating circuit and a resistance parameter generating circuit. The test Bluetooth wireless transceiver module, the voice broadcast module, the TFT color display circuit, the matrix keyboard circuit, the voltage parameter generating circuit, the current parameter generating circuit and the resistance parameter generating circuit are all connected to the test end controller circuit, and the test Bluetooth wireless transceiver module is wirelessly connected to the detection Bluetooth wireless transceiver module.

[0012] Furthermore, the current parameter generating circuit includes resistors R13-R20, an electronic switch III, an amplifier A2, a transistor Q1 and an electronic single switch S1, the positive input terminal of the amplifier A2 is connected to a power supply, the negative input terminal of the amplifier A2 is respectively connected to a bus of the electronic switch III and one end of the resistor R13, the other end of the resistor R13 is grounded, one end of the resistors R14-R19 is respectively connected to six switch pins of the electronic switch III, the other ends of the resistors R14-R19 are connected to one end of the resistor R20 and the emitter of the transistor Q1, the output end of the amplifier A2 is connected to the base of the transistor Q1, the collector of the transistor Q1 is connected to a +5V power supply via the electronic single switch S1, and both ends of the electronic single switch S1 are connected to the test terminals of the test terminal.

[0013] Furthermore, the resistance parameter generating circuit includes an NMOS tube, an amplifier A3, a resistor R21 and a resistor R22, the G pole of the NMOS tube is connected to a power supply, the D pole of the NMOS tube is connected to a +5V power supply, the S pole of the NMOS tube is respectively connected to the positive input terminal of the amplifier A3 and one end of the resistor R22, the other end of the resistor R22 is connected to the output terminal of the amplifier A3, one end of the resistor R21 is connected to the negative input terminal of the amplifier A3, and the other end is grounded, and the S pole and the D pole of the NMOS tube are connected to the test terminal test terminal.

[0014] Furthermore, the voltage parameter generating circuit includes resistors R23-R27 and an electronic switch IV, one end of the resistor R23 is connected to a +5V power supply, resistors R23-R27 are connected in series, four switch input ends of the electronic switch IV are respectively connected between resistor R23 and resistor R24, between resistor R24 ​​and resistor R25, between resistor R25 and resistor R26, and between resistor R26 and resistor R27, and the bus end of the electronic switch IV is connected to the test terminal of the test terminal.

[0015] The specific process of gear detection is to use the voltage sampling circuit to detect the two ends of the multimeter. If there is voltage detected, it means that the multimeter is in the ohm gear, and then the specific ohm gear is determined according to the voltage. If there is no voltage, the resistance sampling circuit is connected to the test lead of the multimeter, and then the voltage sampling circuit collects U0 at the output end of the resistance sampling circuit. At the same time, the value of the connected feedback resistor is known according to the electronic switch I. The feedback resistor is resistor R8-R12, and then the size of the connected voltage is known through the electronic switch II. Then the ratio of the output voltage to the connected voltage is equal to the ratio of the feedback resistor to the internal resistance of the multimeter, and the internal resistance of the multimeter can be calculated. Then, the size of the internal resistance is analyzed. When the internal resistance is at the ohm level, the multimeter is in the current gear, and the specific gear is determined according to the value. If the internal resistance is at the megohm level, it is the voltage gear, and the specific gear is determined according to the value.

[0016] The present invention adopts the above technical solution, and the present invention has the following technical effects:

[0017] The present invention replaces the electrician's electrician box with a test terminal. The teacher inputs the assessment parameters, which are transmitted wirelessly to the test terminal and then displayed to the students for testing with a multimeter. The multimeter detection protection device then monitors whether the student's gear is correct, thereby realizing remote automatic point deduction. At the same time, the student inputs the measurement results into the test terminal after measurement, and then transmits them back to the teacher, thereby realizing remote multimeter assessment and scoring records, solving the problem of online electrician training assessment during the epidemic situation. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the system of the present invention.

[0019] Figure 2 This is a front view of the test terminal of the present invention.

[0020] Figure 3 This is a cross-sectional view of the test terminal of the present invention.

[0021] Figure 4 It is a front view of the multimeter detection protection device of the present invention.

[0022] Figure 5 It is a side view of the multimeter detection protection device of the present invention.

[0023] Figure 6 The present invention is a block diagram of the principle of a multimeter detection protection circuit of the multimeter detection protection device.

[0024] Figure 7 This is a schematic diagram of the resistance detection circuit of the present invention.

[0025] Figure 8 This is a circuit diagram of the test terminal of the present invention.

[0026] Fig. 9 This is a schematic diagram of a direct current generating circuit of the present invention.

[0027] Fig.10 The figure is a schematic diagram of a resistance generating circuit of the present invention.

[0028] Fig.11 This is a schematic diagram of the DC voltage generation principle of the present invention.

[0029] Numbers in the figure: 1-multimeter; 2-test leads; 3-multimeter detection and protection device; 4-mobile phone; 5-test terminal; 6-teacher terminal; 7-test terminal front shell; 8-test terminal back shell; 9-test terminal power adapter socket; 10-test terminal test terminal; 11-test terminal matrix keyboard; 12-test terminal voice outlet; 13-test terminal TFT color screen; 14-detection and protection device front shell; 15-detection and protection device back shell; 16-multimeter connection terminal; 17-test lead socket. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the present invention more clear, preferred embodiments are given to further describe the present invention in detail. However, it should be noted that many details listed in the specification are only for the purpose of enabling readers to have a thorough understanding of one or more aspects of the present invention, and these aspects of the present invention can be implemented even without these specific details.

[0031] A pointer multimeter online assessment system, such as Figure 1 As shown, it includes a teacher terminal 6 and several assessment terminals, and the several assessment terminals are wirelessly connected to the teacher terminal 6. The assessment terminal includes a multimeter 1, a test lead 2, a multimeter detection protection device 3, a mobile phone 4 and a test terminal 5. The test lead 2 is connected to the multimeter 1 via the multimeter detection protection device 3, the test head of the test lead 2 is connected to the test terminal 5, and the test terminal 5 is wirelessly connected to the teacher terminal 6 via the mobile phone 4.

[0032] The assessment end is directly distributed to students, and students can complete the assessment of the multimeter in the dormitory. During the assessment, the parameters of the voltage, current and resistance of the assessment are input into the teacher end 6, and then transmitted to the mobile phone 4 of each student, and transmitted through the Internet. The teacher end 6 is a computer, and an existing software is installed on the mobile phone 4 of each student to receive the measurement data of the teacher end, and then the mobile phone 4 transmits the data to the test terminal 5. There is also another situation in which the teacher end 6 can be directly connected to the test terminal 5, but the test terminal 5 needs to be equipped with a flow card, which is more expensive. After the test terminal 5 receives the data of the teacher end 6, it is displayed on the display screen, and the test port is controlled to output the corresponding voltage, current and resistance parameters, and then the students use the multimeter 1 to measure. The measured data is read by keyboard input measurement. Wherein the multimeter 1 is connected to a multimeter detection protection device 3 for protection.

[0033] In the embodiment of the present invention, Figure 4-5 As shown, the multimeter detection and protection device 3 includes a detection and protection device front shell 14, a detection and protection device rear shell 15, a multimeter connection terminal 16 and a test pen socket 17. The detection and protection device front shell 14 and the detection and protection device rear shell 15 are covered and arranged, and a multimeter detection and protection circuit is arranged inside. The multimeter connection terminal 16 is arranged on the side of the detection and protection device front shell 14 and is connected to the test pen of the multimeter 1. The test pen socket 17 is arranged at the front end of the detection and protection device front shell 14 and is connected to the test pen 2. The multimeter detection and protection circuit is connected to the multimeter connection terminal 16 and the test pen socket 17. The multimeter connection terminal 16 is used to connect the measurement pen of the multimeter 1. The measurement pen of the multimeter 1 is directly inserted into the multimeter connection terminal 16, and then at the beginning, the multimeter detection and protection device 3 is in a disconnected state. The test pen socket 17 is inserted into the test terminal for measurement.

[0034] In the embodiment of the present invention, Figure 2-3 As shown, the test terminal 5 includes a test terminal front shell 7, a test terminal rear shell 8, a test terminal power adapter socket 9, a test terminal test terminal 10, a test terminal matrix keyboard 11, a test terminal voice outlet 12 and a test terminal TFT color screen 13. The test terminal front shell 7 and the test terminal rear shell 8 are covered and arranged, and a test circuit is arranged inside. The test terminal power adapter socket 9 is arranged on the side of the test terminal front shell 7, and the test terminal test terminal 10, the test terminal matrix keyboard 11, the test terminal voice outlet 12 and the test terminal TFT color screen 13 are arranged at the front end of the test terminal front shell 7. The test terminal power adapter socket 9, the test terminal test terminal 10, the test terminal matrix keyboard 11, the test terminal voice outlet 12 and the test terminal TFT color screen 13 are all connected to the test circuit.

[0035] The test terminal power adapter socket 9 is used to connect an external power line, and the test terminal test terminal 10 is used to generate current, resistance or voltage for students to measure. The test terminal matrix keyboard 11 is used for students to input measurement result data. The test terminal voice output hole 12 is used for voice broadcast to prompt students to measure resistance, voltage or current, and specific data values. The test terminal TFT color screen 13 displays specific measurement input data.

[0036] In the embodiment of the present invention, Figure 6As shown, the multimeter detection protection circuit includes a switching protection circuit, a detection controller circuit, a gear detection circuit and a detection Bluetooth wireless transceiver module, wherein the switching protection circuit, the gear detection circuit and the detection Bluetooth wireless transceiver module are all connected to the detection controller circuit, the detection end of the gear detection circuit is connected to the input end of the switching protection circuit, the input end of the switching protection circuit is connected to the multimeter 1, and the output end of the switching protection circuit is connected to the test terminal 5. The switching protection circuit is a relay, and its input control end is connected to the detection controller circuit to control opening or closing. At the beginning, the switching protection circuit is disconnected, and when the gear detected by the gear detection circuit is compared with the measured value output by the test terminal, the switching protection circuit is closed when the multimeter will not be burned, otherwise, it is not closed. When the student has reached the corresponding gear, the test terminal will prompt whether it has been determined, and when the student is determined by the key input, when the gear is not correct, points will be deducted, and if it is correct, the protection switch will be closed. The detection controller circuit is the minimum system of the STM32F4 single-chip microcomputer. The detection Bluetooth wireless transceiver module is an existing Bluetooth module.

[0037] In the embodiment of the present invention, the gear detection circuit includes a voltage sampling circuit and a resistance sampling circuit, the output end of the voltage sampling circuit is connected to the detection controller circuit, and the sampling end of the voltage sampling circuit is respectively connected to the output end of the resistance sampling circuit and the input end of the switching protection circuit. First, the voltage of the multimeter is sampled. When there is no voltage, it means that it is not the ohm gear, then the resistance sampling circuit is connected to the multimeter, and then the voltage sampling circuit collects the output voltage of the resistance sampling circuit, and then the internal resistance of the multimeter is calculated according to the voltage, and the corresponding current gear or voltage gear is obtained. The specific gear is related to the corresponding resistance (the corresponding value is used as a reference on the pointer multimeter).

[0038] In the embodiment of the present invention, Figure 7As shown, the resistance sampling circuit includes resistors R1-R12, an electronic switch I, an electronic switch II and an amplifier A1, one end of the resistor R1 is connected to a +5V power supply, resistors R1-R5 are connected in series, four switch input ends of the electronic switch I are respectively connected between the resistor R1 and the resistor R2, between the resistor R2 and the resistor R3, between the resistor R3 and the resistor R4, and between the resistor R4 and the resistor R5, the bus end of the electronic switch I is connected to an input end of the switching protection circuit, the other input end of the switching protection circuit is connected to the bus end of the electronic switch II and the positive input end of the amplifier A1, one end of the resistor R6 is grounded, and the other end is connected to the negative input end of the amplifier A1, one end of the resistor R7-R12 is respectively connected to the six switch pins of the sub-switch II, and the other ends are all connected to the output end of the amplifier A1, and the sampling end of the voltage sampling circuit is connected to the output end of the amplifier A1. The specific process of gear detection is to use the voltage sampling circuit to detect the two ends of the multimeter. If there is voltage detected, it means that the multimeter is in the ohm gear, and then the specific ohm gear is determined according to the voltage. If there is no voltage, the resistance sampling circuit is connected to the test lead of the multimeter, and then the voltage sampling circuit collects U0 at the output end of the resistance sampling circuit. At the same time, the value of the connected feedback resistor is known according to the electronic switch I. The feedback resistor is resistor R8-R12, and then the size of the connected voltage is known through the electronic switch II. Then the ratio of the output voltage to the connected voltage is equal to the ratio of the feedback resistor to the internal resistance of the multimeter, and the internal resistance of the multimeter can be calculated. Then, the size of the internal resistance is analyzed. When the internal resistance is at the ohm level, the multimeter is in the current gear, and the specific gear is determined according to the value. If the internal resistance is at the megohm level, it is the voltage gear, and the specific gear is determined according to the value.

[0039] The sampling voltage U0 is equal to the resistance value of one of the resistors R7-R12 and the internal resistance value of the multimeter. Then we know which one of the resistors R7-R12 is closed. Then we can get the internal resistance value of the multimeter by taking the ratio of the resistance of this path and the sampling voltage U0, and then we can get the specific gear of the corresponding voltage or current. Resistors R1-R5 and electronic switch I are used to input different voltages.

[0040] In the embodiment of the present invention, Figure 8 As shown, the test circuit includes a test Bluetooth wireless transceiver module, a voice broadcast module, a test end controller circuit, a TFT color display circuit, a matrix keyboard circuit, a voltage parameter generating circuit, a current parameter generating circuit and a resistance parameter generating circuit. The test Bluetooth wireless transceiver module, the voice broadcast module, the TFT color display circuit, the matrix keyboard circuit, the voltage parameter generating circuit, the current parameter generating circuit and the resistance parameter generating circuit are all connected to the test end controller circuit, and the test Bluetooth wireless transceiver module is wirelessly connected to the detection Bluetooth wireless transceiver module.

[0041] The test end controller circuit is the existing STM32F4 single chip microcomputer minimum system. The test Bluetooth wireless transceiver module and voice broadcast module are existing modules, and the voltage parameter generation circuit, current parameter generation circuit and resistance parameter generation circuit are used to generate corresponding voltage, current and resistance.

[0042] In the embodiment of the present invention, Fig. 9 As shown, the current parameter generating circuit includes resistors R13-R20, an electronic switch III, an amplifier A2, a transistor Q1 and an electronic single switch S1, the positive input end of the amplifier A2 is connected to the power supply, the negative input end of the amplifier A2 is respectively connected to the bus of the electronic switch III and one end of the resistor R13, the other end of the resistor R13 is grounded, one end of the resistors R14-R19 is respectively connected to the six switch pins of the electronic switch III, the other ends of the resistors R14-R19 are all connected to one end of the resistor R20 and the emitter of the transistor Q1, the output end of the amplifier A2 is connected to the base of the transistor Q1, the collector of the transistor Q1 is connected to the +5V power supply via the electronic single switch S1, and the two ends of the electronic single switch S1 are connected to the test terminal test terminal 10.

[0043] During measurement, the electronic single switch S1 is disconnected, allowing current to flow into the multimeter, and then the voltage output by the amplifier A2 controls the transistor Q1 to conduct, so that the test end outputs current, and then the value of the output current is related to the feedback resistor R14-R19. The ratio of the output current to the input current is the ratio of one of the resistors R14-R19 to the resistor R20. By changing the connection of the resistors R14-R19, different currents can be obtained.

[0044] In the embodiment of the present invention, Fig.10 As shown, the resistance parameter generating circuit includes an NMOS tube, an amplifier A3, a resistor R21 and a resistor R22, the G pole of the NMOS tube is connected to the power supply, the D pole of the NMOS tube is connected to the +5V power supply, the S pole of the NMOS tube is respectively connected to the positive input terminal of the amplifier A3 and one end of the resistor R22, the other end of the resistor R22 is connected to the output end of the amplifier A3, one end of the resistor R21 is connected to the negative input terminal of the amplifier A3, and the other end is grounded, and the S pole and the D pole of the NMOS tube are connected to the test terminal test terminal 10.

[0045] This circuit changes the G-pole input voltage of the NMOS tube to make the channel of the NMOS tube smaller or larger, generating different resistances, that is, the resistance between the S-pole and the D-pole, and then passes through the output voltage of the sampling amplifier A3, and then changes the input voltage value to obtain different resistance values, which all correspond to the measurement parameters set at the original teacher end.

[0046] The voltage parameter generating circuit includes resistors R23-R27 and an electronic switch IV, one end of the resistor R23 is connected to a +5V power supply, the resistors R23-R27 are connected in series, the four switch input ends of the electronic switch IV are respectively connected between the resistor R23 and the resistor R24, between the resistor R24 ​​and the resistor R25, between the resistor R25 and the resistor R26, and between the resistor R26 and the resistor R27, and the bus end of the electronic switch IV is connected to the test terminal 10 of the test terminal. Different voltages are mainly generated for measurement in the form of voltage division.

[0047] The above is only 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 principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A pointer multimeter online assessment system, characterized in that: The apparatus comprises a teacher terminal (6) and a plurality of assessment terminals, wherein the plurality of assessment terminals are wirelessly connected to the teacher terminal (6), the assessment terminal comprises a multimeter (1), a test lead (2), a multimeter detection protection device (3), a mobile phone (4) and a test terminal (5), wherein the test lead (2) is connected to the multimeter (1) via the multimeter detection protection device (3), the test head of the test lead (2) is connected to the test terminal (5), and the test terminal (5) is wirelessly connected to the teacher terminal (6) via the mobile phone (4); The multimeter detection protection device (3) is provided with a resistance sampling circuit, the resistance sampling circuit comprising resistors R1-R12, an electronic switch I, an electronic switch II and an amplifier A1, one end of the resistor R1 is connected to a +5V power supply, the resistors R1-R5 are connected in series, the four switch input ends of the electronic switch I are respectively connected between the resistor R1 and the resistor R2, between the resistor R2 and the resistor R3, between the resistor R3 and the resistor R4, and between the resistor R4 and the resistor R5, the bus end of the electronic switch I is connected to an input end of the switching protection circuit, the other input end of the switching protection circuit is connected to the bus end of the electronic switch II and the positive input end of the amplifier A1, one end of the resistor R6 is grounded, and the other end is connected to the negative input end of the amplifier A1, one end of the resistors R7-R12 are respectively connected to the six switch pins of the sub-switch II, and the other ends are all connected to the output end of the amplifier A1, and the sampling end of the voltage sampling circuit is connected to the output end of the amplifier A1; The specific process of gear detection is to use the voltage sampling circuit to detect the two ends of the multimeter. If there is voltage detected, it means that the multimeter is in the ohm gear, and then the specific ohm gear is determined according to the voltage. If there is no voltage, the resistance sampling circuit is connected to the test lead of the multimeter, and then the voltage sampling circuit collects U0 at the output end of the resistance sampling circuit. At the same time, the value of the connected feedback resistor is known according to the electronic switch I. The feedback resistor is resistor R8-R12, and then the size of the connected voltage is known through the electronic switch II. Then the ratio of the output voltage to the connected voltage is equal to the ratio of the feedback resistor to the internal resistance of the multimeter, and the internal resistance of the multimeter can be calculated. Then, the size of the internal resistance is analyzed. When the internal resistance is at the ohm level, the multimeter is in the current gear, and the specific gear is determined according to the value. If the internal resistance is at the megohm level, it is the voltage gear, and the specific gear is determined according to the value.

2. The online assessment system for pointer multimeter according to claim 1, characterized in that: The multimeter detection protection device (3) comprises a detection protection device front shell (14), a detection protection device rear shell (15), a multimeter connection terminal (16) and a test pen socket (17); the detection protection device front shell (14) and the detection protection device rear shell (15) are arranged to cover each other, and a multimeter detection protection circuit is arranged inside; the multimeter connection terminal (16) is arranged on the side of the detection protection device front shell (14) and is connected to the test pen of the multimeter (1); the test pen socket (17) is arranged at the front end of the detection protection device front shell (14) and is connected to the test pen (2); and the multimeter detection protection circuit is connected to the multimeter connection terminal (16) and the test pen socket (17).

3. The online assessment system for pointer multimeter according to claim 2, characterized in that: The test terminal (5) comprises a test terminal front shell (7), a test terminal rear shell (8), a test terminal power adapter socket (9), a test terminal test terminal terminal (10), a test terminal matrix keyboard (11), a test terminal voice outlet (12) and a test terminal TFT color screen (13); the test terminal front shell (7) and the test terminal rear shell (8) are arranged to cover each other and a test circuit is arranged inside; the test terminal power adapter socket (9) is arranged on the side of the test terminal front shell (7); the test terminal test terminal (10), the test terminal matrix keyboard (11), the test terminal voice outlet (12) and the test terminal TFT color screen (13) are arranged at the front end of the test terminal front shell (7); and the test terminal power adapter socket (9), the test terminal test terminal (10), the test terminal matrix keyboard (11), the test terminal voice outlet (12) and the test terminal TFT color screen (13) are all connected to the test circuit.

4. The online assessment system for pointer multimeter according to claim 3 is characterized in that: The multimeter detection protection circuit comprises a switching protection circuit, a detection controller circuit, a gear detection circuit and a detection Bluetooth wireless transceiver module. The switching protection circuit, the gear detection circuit and the detection Bluetooth wireless transceiver module are all connected to the detection controller circuit. The detection end of the gear detection circuit is connected to the input end of the switching protection circuit. The input end of the switching protection circuit is connected to the multimeter (1). The output end of the switching protection circuit is connected to the test terminal (5).

5. The online assessment system for pointer multimeter according to claim 4 is characterized in that: The gear detection circuit includes a voltage sampling circuit and a resistance sampling circuit. The output end of the voltage sampling circuit is connected to the detection controller circuit, and the sampling end of the voltage sampling circuit is respectively connected to the output end of the resistance sampling circuit and the input end of the switching protection circuit.

6. The online assessment system for pointer multimeter according to claim 3 is characterized in that: The test circuit includes a test Bluetooth wireless transceiver module, a voice broadcast module, a test end controller circuit, a TFT color display circuit, a matrix keyboard circuit, a voltage parameter generating circuit, a current parameter generating circuit and a resistance parameter generating circuit. The test Bluetooth wireless transceiver module, the voice broadcast module, the TFT color display circuit, the matrix keyboard circuit, the voltage parameter generating circuit, the current parameter generating circuit and the resistance parameter generating circuit are all connected to the test end controller circuit, and the test Bluetooth wireless transceiver module is wirelessly connected to the detection Bluetooth wireless transceiver module.

7. The online assessment system for pointer multimeter according to claim 6, characterized in that: The current parameter generating circuit comprises resistors R13-R20, an electronic switch III, an amplifier A2, a transistor Q1 and an electronic single switch S1, wherein the positive input terminal of the amplifier A2 is connected to a power supply, the negative input terminal of the amplifier A2 is respectively connected to a bus of the electronic switch III and one end of the resistor R13, the other end of the resistor R13 is grounded, one end of the resistors R14-R19 is respectively connected to six switch pins of the electronic switch III, the other ends of the resistors R14-R19 are all connected to one end of the resistor R20 and the emitter of the transistor Q1, the output end of the amplifier A2 is connected to the base of the transistor Q1, the collector of the transistor Q1 is connected to a +5V power supply via the electronic single switch S1, and both ends of the electronic single switch S1 are connected to a test terminal test terminal (10).

8. The online assessment system for pointer multimeter according to claim 7 is characterized in that: The resistance parameter generating circuit comprises an NMOS tube, an amplifier A3, a resistor R21 and a resistor R22, wherein the G pole of the NMOS tube is connected to a power supply, the D pole of the NMOS tube is connected to a +5V power supply, the S pole of the NMOS tube is respectively connected to the positive input terminal of the amplifier A3 and one end of the resistor R22, the other end of the resistor R22 is connected to the output terminal of the amplifier A3, one end of the resistor R21 is connected to the negative input terminal of the amplifier A3, and the other end is grounded, and the S pole and the D pole of the NMOS tube are connected to a test terminal (10).

9. The pointer multimeter online assessment system according to claim 8, characterized in that: The voltage parameter generating circuit comprises resistors R23-R27 and an electronic switch IV, one end of the resistor R23 is connected to a +5V power supply, the resistors R23-R27 are connected in series, the four switch input ends of the electronic switch IV are respectively connected between the resistor R23 and the resistor R24, between the resistor R24 ​​and the resistor R25, between the resistor R25 and the resistor R26, and between the resistor R26 and the resistor R27, and the bus end of the electronic switch IV is connected to a test terminal (10) of a test terminal.

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