A measuring device for the resistance of a pyrotechnic charge

Abstract

The utility model discloses a kind of measuring device suitable for initiating explosive resistance, including precision bidirectional direct current constant current source, bidirectional program-controlled gain amplifier, AD conversion circuit, single-chip microcomputer control circuit, system power module, keyboard input circuit and liquid crystal display. The utility model has adopted intermittent bidirectional pulse to replace continuous bidirectional pulse, without reducing test precision, without changing test current amplitude, reducing test current effective value, shorten the time of current applied on the measured initiating explosive resistance, the heat generated by the measured initiating explosive resistance in the current pulse duty cycle is 50% in the same test time can be reduced by half, improve the safety of initiating explosive resistance measurement.

Description

Technical Field

[0001] This utility model relates to a measuring device suitable for measuring the resistance of pyrotechnic products. Background Technology

[0002] With the development of electronic technology, the field of automatic measurement technology has also developed rapidly. Pyrotechnic resistance measuring instruments utilize microcontroller control technology and are widely used in aerospace, weaponry, and other industries. They achieve automatic zeroing and automatic range switching functions, and the resistance value of pyrotechnics is tested based on Ohm's law. For safety reasons, the test current for pyrotechnic resistance must be strictly limited to a very small value (below 10mA), and the test circuit should also minimize the application time of the test current to eliminate the danger caused by prolonged energization of the pyrotechnic by the testing instrument.

[0003] In the patent document with patent number ZL200910227053.6, a single-chip microcomputer is used as the control core. A computer-controlled bidirectional precision DC constant current source and a bidirectional programmable gain amplifier are used. By changing the direction of the test current and the gain of the amplifier, the voltage value of the resistance of the tested pyrotechnic device under test current in different directions is obtained, which eliminates the directional interference potential in the test process. However, it adopts bidirectional pulse test, and the test current is continuous and uninterrupted, which makes the test current continuously loaded on the resistance of the tested pyrotechnic device, which is not conducive to improving the safety of the test. Utility Model Content

[0004] To solve the above-mentioned technical problems, this utility model provides a simple, safe and reliable measuring device for the resistance of pyrotechnic products.

[0005] The technical solution of this utility model to solve the above-mentioned technical problems is as follows: a measuring device suitable for the resistance of pyrotechnic products, including a precision bidirectional DC constant current source, a bidirectional programmable gain amplifier, an AD conversion circuit, a microcontroller control circuit, and a system power module, wherein the system power module provides working power for the entire measuring device; the precision bidirectional DC constant current source, the bidirectional programmable gain amplifier, the AD conversion circuit, and the microcontroller control circuit are connected in sequence, and the microcontroller control circuit is connected to the precision bidirectional DC constant current source and the bidirectional programmable gain amplifier respectively; the precision bidirectional DC constant current source generates a positive and negative intermittent pulse constant current under the control of the microcontroller control circuit, and the current is sent to the resistance of the pyrotechnic product under test through the TEST1 terminal and the TEST2 terminal; the voltage signal across the resistance of the pyrotechnic product under test is sent to the bidirectional programmable gain amplifier through the TEST1 terminal and the TEST2 terminal; the microcontroller control circuit automatically controls the gain of the amplifier according to the magnitude of the voltage signal strength; the amplified signal is processed by the AD conversion circuit and then the microcontroller control circuit obtains the digital resistance value; each test result is the result obtained by averaging the two results of the resistance of the pyrotechnic product under test with two test currents in positive and negative directions respectively.

[0006] The aforementioned measuring device for the resistance of pyrotechnic products includes a precision bidirectional DC constant current source comprising a first operational amplifier, a first bidirectional analog switch, a second bidirectional analog switch, a third bidirectional analog switch, a fourth bidirectional analog switch, a first field-effect transistor (FET), a second field-effect transistor (FET), a third field-effect transistor (FET), a fourth field-effect transistor (FET), a first precision resistor, a second precision resistor, and a third precision resistor. The non-inverting input of the first operational amplifier is connected to one end of the second precision resistor and one end of the third precision resistor. The other end of the second precision resistor is connected to a 2.5V reference voltage, and the other end of the third precision resistor is grounded. The inverting input of the first operational amplifier is connected to the 2.5V reference voltage via the first precision resistor. The inverting input of the first operational amplifier is connected to the drain of the first field-effect transistor via the second bidirectional analog switch. The source of the first field-effect transistor is... After being connected to the gate, the first operational amplifier's inverting input is connected to the drain of the second field-effect transistor (FET) via the fourth bidirectional analog switch. The second FET's source and gate are connected together and then connected to the TEST2 terminal. The first operational amplifier's output is connected to the source and gate of the third FET via the first bidirectional analog switch. The third FET's drain is connected to the TEST2 terminal. The first operational amplifier's output is connected to the source and gate of the fourth FET via the third bidirectional analog switch. The fourth FET's drain is connected to the TEST1 terminal. The control terminals of the first, second, third, and fourth bidirectional analog switches are connected to the microcontroller control circuit. The resistance of the pyrotechnic device under test is connected between the TEST1 and TEST2 terminals.

[0007] The aforementioned measuring device for the resistance of pyrotechnic items comprises a DC constant current source consisting of a 2.5V reference voltage, a first precision resistor, a second precision resistor, a third precision resistor, and a first operational amplifier; a first field-effect transistor, a second field-effect transistor, a third field-effect transistor, and a fourth field-effect transistor connected in the form of constant current tubes ensure that the test current does not exceed the saturation leakage current, thereby providing current limiting protection in fault conditions; a first bidirectional analog switch, a second bidirectional analog switch, a third bidirectional analog switch, and a fourth bidirectional analog switch are used to change the direction of the test current through the resistance of the pyrotechnic item being measured.

[0008] The aforementioned measuring device for the resistance of pyrotechnic products includes a bidirectional programmable gain amplifier comprising an instrumentation amplifier, a second operational amplifier, a fifth bidirectional analog switch, a sixth bidirectional analog switch, a seventh bidirectional analog switch, a fourth precision resistor, a fifth precision resistor, a sixth precision resistor, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a first level conversion switch, a second level conversion switch, a third level conversion switch, a fourth level conversion switch, and a fifth level conversion switch. The non-inverting input of the instrumentation amplifier is connected to the TEST1 terminal, the inverting input of the instrumentation amplifier is connected to the TEST2 terminal, and the output of the instrumentation amplifier is connected to the non-inverting input of the second operational amplifier. The inverting input of the second operational amplifier is connected to one end of the fifth bidirectional analog switch, one end of the sixth bidirectional analog switch, and one end of the seventh bidirectional analog switch. The other end of the fifth bidirectional analog switch is connected to the output of the second operational amplifier and one end of the fourth precision resistor. The output of the second operational amplifier is connected to an AD conversion circuit. The other end of the sixth bidirectional analog switch is connected to the other end of the fourth precision resistor and one end of the fifth precision resistor. The other end of the seventh bidirectional analog switch is connected to the other end of the fifth precision resistor and one end of the sixth precision resistor. The other end of the sixth precision resistor is grounded. The control terminal of the bidirectional analog switch is connected to the collector of the first level-shifting switch and one end of the first resistor. The control terminal of the sixth bidirectional analog switch is connected to the collector of the second level-shifting switch and one end of the second resistor. The control terminal of the seventh bidirectional analog switch is connected to the collector of the third level-shifting switch and one end of the third resistor. The collector of the fourth level-shifting switch is connected to one end of the fourth resistor, the control terminal of the first bidirectional analog switch, and the control terminal of the second bidirectional analog switch. The collector of the fifth level-shifting switch is connected to one end of the fifth resistor, the control terminal of the third bidirectional analog switch, and the control terminal of the fourth bidirectional analog switch. The first resistor... The other ends of the first resistor, the second resistor, the third resistor, the fourth resistor, and the fifth resistor are connected together and then connected to a +5V voltage. The emitters of the first, second, third, fourth, and fifth level conversion transistors are connected together and then connected to a -5V voltage. The bases of the first, second, third, fourth, and fifth level conversion transistors are connected to the microcontroller control circuit.

[0009] The above-mentioned measuring device for the resistance of pyrotechnic products has an instrumentation amplifier configured in a unity-gain configuration, which serves as an analog level converter. The voltage signal across the resistor of the pyrotechnic product being measured is input from the instrumentation amplifier, and the signal after level conversion is sent to the second operational amplifier. The gain of the second operational amplifier is controlled by a microcontroller control circuit to achieve three fixed gains of 1, 10, and 100.

[0010] The above-mentioned device for measuring the resistance of pyrotechnic products uses a PIC18F458-I / P microcontroller as the main chip of the microcontroller control circuit. The RB1 pin of the microcontroller is connected to the base of the first level conversion switch transistor via the sixth resistor, the RB2 pin is connected to the base of the second level conversion switch transistor via the seventh resistor, the RB6 pin is connected to the base of the third level conversion switch transistor via the eighth resistor, the RB7 pin is connected to the base of the fourth level conversion switch transistor via the ninth resistor, and the RA0 pin is connected to the base of the fourth level conversion switch transistor via the tenth resistor.

[0011] The above-mentioned measuring device for the resistance of pyrotechnic products uses the ICL7135 as the mutual chip in the AD conversion circuit. It utilizes the characteristic that the width of the BUSY positive signal pulse is proportional to its input signal, and measures the width of the BUSY positive signal pulse by means of edge-triggered interrupt of the microcontroller, and calculates the value of the measured voltage signal.

[0012] The aforementioned measuring device for the resistance of pyrotechnic products also includes a keyboard input circuit. The keyboard input circuit consists of eight switch input circuits composed of parallel-in-serial integrated circuits and resistor arrays. The keyboard input circuit sends eight switch signals to the microcontroller in a serial manner.

[0013] The aforementioned measuring device for the resistance of pyrotechnic products also includes a liquid crystal display (LCD), which is connected to a microcontroller to display measurement results and various Chinese prompts.

[0014] The beneficial effects of this utility model are as follows: This utility model uses intermittent bidirectional pulses instead of continuous bidirectional pulses, without reducing the test accuracy or changing the test current amplitude, but reducing the effective value of the test current and shortening the time the current is applied to the resistance of the pyrotechnic device under test. The heat generated by the resistance of the pyrotechnic device under test during the same test time can be reduced by half when the current pulse duty cycle is 50%, thus improving the safety of pyrotechnic device resistance measurement. Attached Figure Description

[0015] Figure 1 This is a block diagram of the overall structure of the measuring device in this utility model.

[0016] Figure 2 This is the overall circuit diagram of the measuring device in this utility model.

[0017] Figure 3 This is a comparison diagram between the testing method of this utility model and the prior art. Detailed Implementation

[0018] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0019] like Figure 1 As shown, a measuring device suitable for measuring the resistance of pyrotechnic products includes a precision bidirectional DC constant current source 1, a bidirectional programmable gain amplifier 2, an AD conversion circuit 3, a microcontroller control circuit 4, a system power module 7, a keyboard input circuit 5, and an LCD display 6. The system power module 7 provides operating power for the entire measuring device. The precision bidirectional DC constant current source 1, the bidirectional programmable gain amplifier 2, the AD conversion circuit 3, and the microcontroller control circuit 4 are connected in sequence, and the microcontroller control circuit 4 is connected to the precision bidirectional DC constant current source 1 and the bidirectional programmable gain amplifier 2 respectively.

[0020] like Figure 2 As shown, the precision bidirectional DC constant current source 1 generates a positive and negative intermittent pulse constant current under the control of the microcontroller control circuit 4. The current is sent to the resistor Rx of the pyrotechnic device under test through the TEST1 and TEST2 terminals. The voltage signal across the resistor Rx is sent to the bidirectional programmable gain amplifier 2 through the TEST1 and TEST2 terminals. The microcontroller control circuit 4 automatically controls the gain of the amplifier according to the magnitude of the voltage signal. The amplified signal is processed by the AD conversion circuit 3 and then the microcontroller control circuit 4 obtains the digitized resistance value. Each test result is obtained by averaging the two results of passing positive and negative test currents to the resistor Rx of the pyrotechnic device under test.

[0021] The precision bidirectional DC constant current source 1 includes a first operational amplifier U101, a first bidirectional analog switch U102A, a second bidirectional analog switch U102B, a third bidirectional analog switch U102C, a fourth bidirectional analog switch U102D, a first field-effect transistor Q102, a second field-effect transistor Q103, a third field-effect transistor Q104, a fourth field-effect transistor Q105, a first precision resistor R101, a second precision resistor R102, a third precision resistor R103, and a non-inverting phase resistor of the first operational amplifier U101. The input terminal is connected to one end of the second precision resistor R102 and one end of the third precision resistor R103. The other end of the second precision resistor R102 is connected to a 2.5V reference voltage, and the other end of the third precision resistor R103 is grounded. The inverting input terminal of the first operational amplifier U101 is connected to the 2.5V reference voltage via the first precision resistor R101. The inverting input terminal of the first operational amplifier U101 is connected to the drain of the first field-effect transistor Q102 via the second bidirectional analog switch U102B. The first field-effect transistor Q10... The source and gate of transistor Q103 are connected together and then connected to the TEST1 terminal. The inverting input of the first operational amplifier U101 is connected to the drain of the second field-effect transistor Q103 via the fourth bidirectional analog switch U102D. The source and gate of the second field-effect transistor Q103 are connected together and then connected to the TEST2 terminal. The output of the first operational amplifier U101 is connected to the source and gate of the third field-effect transistor Q104 via the first bidirectional analog switch U102A. The drain of the third field-effect transistor Q104 is connected to the TEST2 terminal. The output of the first operational amplifier U101 is connected to the source and gate of the fourth field-effect transistor Q105 via the third bidirectional analog switch U102C. The drain of the fourth field-effect transistor Q105 is connected to the TEST1 terminal. The control terminals of the first bidirectional analog switch U102A, the second bidirectional analog switch U102B, the third bidirectional analog switch U102C, and the fourth bidirectional analog switch U102D are connected to the microcontroller control circuit 4. The resistance Rx of the pyrotechnic device under test is connected between the TEST1 terminal and the TEST2 terminal.

[0022] A reference 2.5V voltage, a first precision resistor R101, a second precision resistor R102, a third precision resistor R103, and a first operational amplifier U101 constitute a DC constant current source; a first field-effect transistor Q102, a second field-effect transistor Q103, a third field-effect transistor Q104, and a fourth field-effect transistor Q105, connected as constant current transistors, ensure that the test current does not exceed the saturation leakage current, thus providing current limiting protection in fault conditions; a first bidirectional analog switch U102A, a second bidirectional analog switch U102B, a third bidirectional analog switch U102C, and a fourth bidirectional analog switch U102D are used to change the direction of the test current through the resistance Rx of the tested pyrotechnic device.

[0023] The bidirectional programmable gain amplifier 2 includes an instrumentation amplifier U201, a second operational amplifier U202, a fifth bidirectional analog switch U103B, a sixth bidirectional analog switch U103C, a seventh bidirectional analog switch U103D, a fourth precision resistor R203, a fifth precision resistor R204, a sixth precision resistor R205, a first resistor R206, a second resistor R207, a third resistor R208, a fourth resistor R209, a fifth resistor R209F, a first level shifting switch Q201, a second level shifting switch Q202, a third level shifting switch Q203, a fourth level shifting switch Q204, a fifth level shifting switch Q204F, and an instrumentation amplifier U201. The non-inverting input of instrumentation amplifier U201 is connected to terminal TEST1. The inverting input of instrumentation amplifier U201 is connected to terminal TEST2. The output of instrumentation amplifier U201 is connected to the non-inverting input of second operational amplifier U202. The inverting input of second operational amplifier U202 is connected to one end of the fifth bidirectional analog switch U103B, one end of the sixth bidirectional analog switch U103C, and one end of the seventh bidirectional analog switch U103D. The other end of the fifth bidirectional analog switch U103B is connected to the output of second operational amplifier U202 and one end of the fourth precision resistor R203. The output of second operational amplifier U202 is connected to AD conversion circuit 3. The sixth bidirectional analog switch U103... The other end of switch C is connected to the other end of the fourth precision resistor R203 and one end of the fifth precision resistor R204. The other end of the seventh bidirectional analog switch U103D is connected to the other end of the fifth precision resistor R204 and one end of the sixth precision resistor R205. The other end of the sixth precision resistor R205 is grounded. The control terminal of the fifth bidirectional analog switch U103B is connected to the collector of the first level conversion switch Q201 and one end of the first resistor R206. The control terminal of the sixth bidirectional analog switch U103C is connected to the collector of the second level conversion switch Q202 and one end of the second resistor R207. The control terminal of the seventh bidirectional analog switch U103D is connected to the collector of the third level conversion switch Q203. The electrodes are connected to one end of the third resistor R208. The collector of the fourth level-shifting switch Q204 is connected to one end of the fourth resistor R209, the control terminal of the first bidirectional analog switch U102A, and the control terminal of the second bidirectional analog switch U102B. The collector of the fifth level-shifting switch Q204F is connected to one end of the fifth resistor R209F, the control terminal of the third bidirectional analog switch U102C, and the control terminal of the fourth bidirectional analog switch U102D. The other ends of the first resistor R206, the second resistor R207, the third resistor R208, the fourth resistor R209, and the fifth resistor R209F are connected together and then connected to a +5V voltage.The emitters of the first level shifter Q201, the second level shifter Q202, the third level shifter Q203, the fourth level shifter Q204, and the fifth level shifter Q204F are connected together and then connected to a -5V voltage. The bases of the first level shifter Q201, the second level shifter Q202, the third level shifter Q203, the fourth level shifter Q204, and the fifth level shifter Q204F are respectively connected to the microcontroller control circuit 4.

[0024] The instrumentation amplifier U201 is configured in unity gain form to perform analog level conversion. The voltage signal across the resistor Rx of the pyrotechnic device under test is input from the instrumentation amplifier U201, and the signal after level conversion is sent to the second operational amplifier U202. The gain of the second operational amplifier U202 is controlled by the microcontroller control circuit 4 to achieve three fixed gains of 1, 10, and 100.

[0025] The main chip of the microcontroller control circuit 4 is a PIC18F458-I / P microcontroller. The RB1 pin of the microcontroller is connected to the base of the first level conversion switch Q201 through the sixth resistor R604. The RB2 pin of the microcontroller is connected to the base of the second level conversion switch Q202 through the seventh resistor R603. The RB6 pin of the microcontroller is connected to the base of the third level conversion switch Q203 through the eighth resistor R602. The RB7 pin of the microcontroller is connected to the base of the fourth level conversion switch Q204 through the ninth resistor R601. The RA0 pin of the microcontroller is connected to the base of the fourth level conversion switch Q204 through the tenth resistor R600.

[0026] The A / D conversion circuit 3 uses the ICL7135 chip. It utilizes the characteristic that the width of the BUSY positive signal pulse is proportional to its input signal. The width of the BUSY positive signal pulse is measured by the edge-triggered interrupt of the microcontroller, and the value of the measured voltage signal is calculated.

[0027] The keyboard input circuit 5 consists of eight switch input circuits composed of parallel-in serial-out integrated circuits and resistor arrays. The keyboard input circuit 5 sends eight switch signals to the microcontroller in a serial manner for inputting various instructions and parameters.

[0028] The LCD display 6 is connected to the microcontroller and is used to display measurement results and various Chinese prompts.

[0029] A method for measuring the resistance of pyrotechnic products is provided. A precision bidirectional DC constant current source 1 generates a positive and negative intermittent pulse constant current, i.e., a test pulse with a duty cycle of 50%, under the control of a single-chip microcomputer control circuit 4. The single-chip microcomputer control circuit 4 provides positive current direction signals IDDZ and negative current direction signals IDDF, respectively. After being converted by a bidirectional programmable gain amplifier 2, the positive output IDDZ and the negative output IDDF are converted into current direction control signals IDZ and IDF, respectively.

[0030] Forward test current I z The process is as follows: When IDDZ is high, IDZ is also high, meaning the control terminals of the first bidirectional analog switch U102A and the second bidirectional analog switch U102B are high. The first bidirectional analog switch U102A and the second bidirectional analog switch U102B are turned on, and a constant current flows sequentially through the first precision resistor R101, the second bidirectional analog switch U102B, the first field-effect transistor Q102, the TEST1 terminal, the TEST2 terminal, the third field-effect transistor Q104, and the first bidirectional analog switch U102A. At this time, the test current is in the positive direction. The positive current is sent to the tested pyrotechnic resistor Rx through the TEST1 and TEST2 terminals. The positive voltage signal U across the tested pyrotechnic resistor Rx... 正 The signal is sent to the bidirectional programmable gain amplifier 2 via the TEST1 and TEST2 terminals. When IDDZ is low, IDZ is also low, and the outputs of the first bidirectional analog switch U102A and the second bidirectional analog switch U102B are cut off.

[0031] Reverse test current I f The process is as follows: When IDDF is high, IDF is also high, meaning the control terminals of the third bidirectional analog switch U102C and the fourth bidirectional analog switch U102D are high, and the third bidirectional analog switch U102C and the fourth bidirectional analog switch U102D are turned on. A constant current flows sequentially through the first precision resistor R101, the fourth bidirectional analog switch U102D, the second field-effect transistor Q103, the TEST2 terminal, the TEST1 terminal, the fourth field-effect transistor Q105, and the third bidirectional analog switch U102C. At this time, the test current is in the reverse direction. The reverse current is sent through the TEST1 terminal and the TEST2 terminal to the tested pyrotechnic resistor Rx. The reverse voltage signal U across the tested pyrotechnic resistor Rx... 反 The signal is sent to bidirectional programmable gain amplifier 2 via TEST1 and TEST2 terminals; when IDDF is low, IDF is also low, and the third bidirectional analog switch U102C and the fourth bidirectional analog switch U102D are activated; the pulse duty cycle of the positive and negative output current can be arbitrarily controlled by controlling the high-level output time of IDDZ and IDDF through the microcontroller.

[0032] like Figure 3 As shown, the measurement method described in the background technology is adopted. Under the control of the single-chip microcomputer control circuit 4, the output test pulse frequency is 5Hz, the period is 200ms, and the forward and reverse test current is 1mA. During the test, the current of the measuring instrument is continuously applied to the resistance R of the pyrotechnic device under test. X At both ends, a total of 5 forward test current pulses and 5 reverse test current pulses are generated within a 1-second test time. The forward and reverse voltage values ​​are averaged and calculated by the microcontroller control circuit to obtain the resistance R of the tested pyrotechnic device. X The actual voltage value is used to calculate the accurate resistance value.

[0033] R X =(U 正1 + U 反1 +U 正2 + U 反2 + U 正3 + U 反4 +U 正4 + U 反4 +U 正5 + U 反5 ) / 10;

[0034] Q RX = I 2 R X t=0.001 2 ×R X ×1=10×10 -6 R X J;

[0035] Among them, U 正1 For the first forward test voltage, U 反1 This is the voltage for the first reverse test, and so on; Q RX I represents the heat generated during the resistance test of the pyrotechnic device; I represents the test current; and t represents the time the test current is applied to the resistance of the pyrotechnic device.

[0036] Using this invention, under the control of the single-chip microcomputer control circuit 4, a test pulse frequency of 5Hz, a period of 200ms, and a duty cycle of 50% is output as intermittent test pulses in both forward and reverse directions. The forward and reverse test currents are 1mA. During the test, the current of the measuring instrument is intermittently applied to the resistance R of the pyrotechnic device under test. X At both ends, a total of 5 forward test current pulses and 5 reverse test current pulses are generated within a 1-second test time. The forward and reverse voltage values ​​are averaged and calculated by the microcontroller control circuit to obtain the resistance R of the tested pyrotechnic device. X The actual voltage value is used to calculate the accurate resistance value.

[0037] R X =(U 正1 + U反1 +U 正2 + U 反2 + U 正3 + U 反4 +U 正4 + U 反4 +U 正5 + U 反5 ) / 10;

[0038] Q RX = I 2 R X t=0.001 2 ×R X ×1 / 2=5×10 -6 R X J;

[0039] Compared with the prior art measurement methods, the present invention does not reduce the resistance R of the pyrotechnic device being measured. X Test accuracy ， The reduced effective value of the test current resulted in a decrease in the resistance R of the pyrotechnic device under test during the test. X The heat generation is reduced by half, which greatly improves the safety of the detection and reduces the energy consumption of the measuring instrument.

Claims

1. A measuring device suitable for measuring the resistance of pyrotechnic products, characterized in that: The device includes a precision bidirectional DC constant current source, a bidirectional programmable gain amplifier, an AD conversion circuit, a microcontroller control circuit, and a system power module, which provides power to the entire measuring device. The precision bidirectional DC constant current source, bidirectional programmable gain amplifier, AD conversion circuit, and microcontroller control circuit are connected sequentially, with the microcontroller control circuit connected to both the precision bidirectional DC constant current source and the bidirectional programmable gain amplifier. Under the control of the microcontroller control circuit, the precision bidirectional DC constant current source generates a bidirectional intermittent pulse constant current. This current is sent to the resistance of the pyrotechnic device under test through terminals TEST1 and TEST2. The voltage signal across the resistance of the pyrotechnic device is sent to the bidirectional programmable gain amplifier through terminals TEST1 and TEST2. The microcontroller control circuit automatically controls the amplifier gain based on the voltage signal strength. The amplified signal is processed by the AD conversion circuit, and the microcontroller control circuit obtains a digitized resistance value. Each test result is obtained by averaging two results obtained by applying two test currents to the resistance of the pyrotechnic device in both directions.

2. The measuring device for the resistance of pyrotechnic products according to claim 1, characterized in that: The precision bidirectional DC constant current source includes a first operational amplifier, a first bidirectional analog switch, a second bidirectional analog switch, a third bidirectional analog switch, a fourth bidirectional analog switch, a first field-effect transistor (FET), a second field-effect transistor (FET), a third field-effect transistor (FET), a fourth field-effect transistor (FET), a first precision resistor, a second precision resistor, and a third precision resistor. The non-inverting input of the first operational amplifier is connected to one end of the second precision resistor and one end of the third precision resistor. The other end of the second precision resistor is connected to a 2.5V reference voltage, and the other end of the third precision resistor is grounded. The inverting input of the first operational amplifier is connected to the 2.5V reference voltage via the first precision resistor. The inverting input of the first operational amplifier is connected to the drain of the first field-effect transistor via the second bidirectional analog switch. The source and gate of the first field-effect transistor are connected together. The first operational amplifier's inverting input is connected to the TEST1 terminal. The second field-effect transistor's drain is connected via the fourth bidirectional analog switch. The second field-effect transistor's source and gate are connected together and then connected to the TEST2 terminal. The first operational amplifier's output is connected via the first bidirectional analog switch to the source and gate of the third field-effect transistor. The third field-effect transistor's drain is connected to the TEST2 terminal. The first operational amplifier's output is connected via the third bidirectional analog switch to the source and gate of the fourth field-effect transistor. The fourth field-effect transistor's drain is connected to the TEST1 terminal. The control terminals of the first, second, third, and fourth bidirectional analog switches are connected to the microcontroller control circuit. The resistance of the pyrotechnic device under test is connected between the TEST1 and TEST2 terminals.

3. The measuring device for the resistance of pyrotechnic products according to claim 2, characterized in that: A DC constant current source is formed by a reference 2.5V voltage, a first precision resistor, a second precision resistor, a third precision resistor, and a first operational amplifier. The first, second, third, and fourth field-effect transistors, connected in the form of constant current tubes, ensure that the test current does not exceed the saturation leakage current, thereby providing current limiting protection in fault conditions. The first, second, third, and fourth bidirectional analog switches are used to change the direction of the test current through the resistance of the tested pyrotechnic device.

4. The measuring device for the resistance of pyrotechnic products according to claim 3, characterized in that: The bidirectional programmable gain amplifier includes an instrumentation amplifier, a second operational amplifier, a fifth bidirectional analog switch, a sixth bidirectional analog switch, a seventh bidirectional analog switch, a fourth precision resistor, a fifth precision resistor, a sixth precision resistor, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a first level shifter, a second level shifter, a third level shifter, a fourth level shifter, and a fifth level shifter. The non-inverting input of the instrumentation amplifier is connected to the TEST1 terminal, and the inverting input is connected to the TEST2 terminal. The output of the instrumentation amplifier is connected to the non-inverting input of the second operational amplifier. The inverting input of the second operational amplifier is connected to one end of the fifth bidirectional analog switch, one end of the sixth bidirectional analog switch, and one end of the seventh bidirectional analog switch. The other end of the fifth bidirectional analog switch is connected to the output of the second operational amplifier and one end of the fourth precision resistor. The output of the second operational amplifier is connected to an AD conversion circuit. The other end of the sixth bidirectional analog switch is connected to the other end of the fourth precision resistor and one end of the fifth precision resistor. The other end of the seventh bidirectional analog switch is connected to the other end of the fifth precision resistor and one end of the sixth precision resistor. The other end of the sixth precision resistor is grounded. The control of the fifth bidirectional analog switch... The control terminal of the sixth bidirectional analog switch is connected to the collector of the second level-shifting switch and one end of the second resistor. The control terminal of the seventh bidirectional analog switch is connected to the collector of the third level-shifting switch and one end of the third resistor. The collector of the fourth level-shifting switch is connected to one end of the fourth resistor, the control terminal of the first bidirectional analog switch, and the control terminal of the second bidirectional analog switch. The collector of the fifth level-shifting switch is connected to one end of the fifth resistor, the control terminal of the third bidirectional analog switch, and the control terminal of the fourth bidirectional analog switch. The other end of the first resistor... The other ends of the second, third, fourth, and fifth resistors are connected together and then connected to a +5V voltage. The emitters of the first, second, third, fourth, and fifth level-shifting transistors are connected together and then connected to a -5V voltage. The bases of the first, second, third, fourth, and fifth level-shifting transistors are connected to the microcontroller control circuit.

5. The measuring device for the resistance of pyrotechnic products according to claim 4, characterized in that: The instrumentation amplifier is configured in unity gain form to perform analog level conversion. The voltage signal across the resistor of the pyrotechnic device under test is input from the instrumentation amplifier, and the signal after level conversion is sent to the second operational amplifier. The gain of the second operational amplifier is controlled by the microcontroller control circuit to achieve three fixed gains of 1, 10, and 100.

6. The measuring device for the resistance of pyrotechnic products according to claim 4, characterized in that: The main chip of the microcontroller control circuit is a PIC18F458-I / P microcontroller. The RB1 pin of the microcontroller is connected to the base of the first level conversion switch through the sixth resistor, the RB2 pin of the microcontroller is connected to the base of the second level conversion switch through the seventh resistor, the RB6 pin of the microcontroller is connected to the base of the third level conversion switch through the eighth resistor, the RB7 pin of the microcontroller is connected to the base of the fourth level conversion switch through the ninth resistor, and the RA0 pin of the microcontroller is connected to the base of the fourth level conversion switch through the tenth resistor.

7. The measuring device for the resistance of pyrotechnic products according to claim 6, characterized in that: The A / D conversion circuit uses the ICL7135 chip. Utilizing the characteristic that the width of the BUSY positive signal pulse is proportional to its input signal, the width of the BUSY positive signal pulse is measured by the edge-triggered interrupt of the microcontroller, and the value of the measured voltage signal is calculated.

8. The measuring device for the resistance of pyrotechnic products according to claim 1, characterized in that: It also includes a keyboard input circuit, which consists of eight switch input circuits composed of parallel-in serial-out integrated circuits and resistor arrays. The keyboard input circuit sends eight switch signals to the microcontroller in a serial manner.

9. The measuring device for the resistance of pyrotechnic products according to claim 1, characterized in that: It also includes an LCD display, which is connected to the microcontroller to display measurement results and various Chinese prompts.

Images