High-precision current-limiting resistance measuring circuit and measuring method

Abstract

The invention relates to a high-precision current-limiting resistance measuring circuit and a measuring method, and belongs to the field of term electronics and the field of measurement. The high-precision current-limiting resistor measuring circuit comprises a measured resistor, an instrument amplifier and an ADC, and further comprises a voltage division circuit, the voltage division circuit comprises a resistor R1 and a resistor R2, the resistor R1 and the resistor R2 are connected to the two ends of the measured resistor in series respectively, the other end of the resistor R1 is connected with a power source, and the other end of the resistor R2 is grounded; the two ends of the tested resistor are connected with the ADC through the instrument amplifier, so that the voltage values at the two ends are adjusted to the middle of the ADC acquisition range. The method has the following advantages: 1, the method has the characteristics of high precision and multiple channels; 2, the current-limiting resistance is measured by adopting a voltage division method, the circuit is simple, and the cost is low; and 3, the voltage division circuit adopts R1 and R2 to indirectly measure the measured resistor, so that the voltage division value is in the middle of the ADC acquisition range, edge acquisition is avoided, and the correctness of acquired data is enhanced.

Description

Technical Field

[0001] The invention relates to a high-precision current-limiting resistor measurement circuit and a measurement method, and belongs to the fields of electronics and measurement. Background Art

[0002] At present, the measurement of the current limiting resistor on the missile is of great significance, because the normal operation of the entire missile electronic system is closely related to it. According to the characteristics of the resistor to be measured (current limiting resistor), it is about 3 ohms and needs to meet the measurement accuracy requirement of 2%. Ordinary resistance measurement cannot reach the accuracy. Summary of the invention

[0003] The object of the present invention is to provide a high-precision current-limiting resistance measuring circuit with high measuring accuracy and high reliability.

[0004] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a high-precision current-limiting resistance measurement circuit, including a measured resistor, an instrument amplifier, an ADC, and a voltage divider circuit, wherein the voltage divider circuit includes a resistor R1 and a resistor R2, wherein the resistor R1 and the resistor R2 are respectively connected in series at two ends of the measured resistor, the other end of the resistor R1 is connected to a power supply, and the other end of the resistor R2 is grounded; the two ends of the measured resistor are connected to the ADC through the instrument amplifier, so that the voltage values ​​at both ends are adjusted to the middle of the ADC acquisition range.

[0005] Preferably, the voltage divider circuit further includes a self-detection resistor, which is connected in parallel with the resistor to be measured, and whose two ends are respectively connected in series with the resistor R1 and the resistor R2.

[0006] Preferably, a switch S is provided between the self-test resistor and the resistor R1 and between the resistor to be tested and the resistor R1, and the switches are used to connect the voltage divider circuits respectively.

[0007] Preferably, the resistance values ​​of the resistor R1 and the resistor R2 are equal.

[0008] Preferably, the resistor R1 and the resistor R2 have a value of 50 ohms.

[0009] Preferably, the ADC uses STM32F4 as the main control, which has a 12-bit high-precision ADC module and 24 channels.

[0010] Preferably, the ADC sampling period is configured as 20 periods, the conversion period is set to 88 clock periods, and the ADC data is collected ten times to obtain an average value.

[0011] Another object of the present invention is to provide a high-precision current limiting resistor measurement method, using a high-precision current limiting resistor measurement circuit with a self-test resistor, comprising the following steps:

[0012] (1) When the system is initially running, the self-test resistor Ri is connected. After amplification by the instrumentation amplifier, the ADC collects the voltage and calculates its measured value, which is then compared with the true value to verify that the circuit functions normally and complete the circuit self-test;

[0013] (2) After self-test, the voltage divider circuit is connected to the resistance Rt to be measured.

[0014] Compared with the prior art, the present invention has the following advantages:

[0015] 1. Use STM32F4 as the main control, which has a 12-bit high-precision ADC module and 24 channels, with high-precision multi-channel characteristics;

[0016] 2. Use the voltage division method to measure the current limiting resistor, the circuit is simple and the cost is low;

[0017] 3. The voltage divider circuit uses R1 and R2 to indirectly measure the measured resistance, so that the voltage divider value is in the middle of the ADC acquisition range, avoiding edge acquisition and enhancing the accuracy of the acquired data. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the module composition of an embodiment of the present invention;

[0019] Figure 2 1 is a schematic diagram of a resistance measurement circuit in an embodiment of the present invention. DETAILED DESCRIPTION

[0020] The following is combined with Figure 1-2 The present invention is further described in detail: A high-precision current limiting resistor measurement circuit adopts the following technical solutions:

[0021] 1. Use a voltage divider circuit to test the measured resistance Rt. The voltage divider circuit adds a self-test resistor Ri. The self-test resistor Ri is connected in parallel with the measured resistance Rt, and the connection ends of the two with the resistance R1 are connected or disconnected through a switch S (Ri is connected, Rt is disconnected, and Ri is disconnected, Rt is connected). Measure the self-test resistor Ri, and compare the measured value with the standard value to achieve the self-test function of the circuit;

[0022] 2. To reduce power consumption and heat generation, two larger resistors are connected in series at both ends of the resistor Rt under test in the voltage divider circuit: resistor R1 and resistor R2. The other end of resistor R1 is connected to the power supply V_Power, and the other end of resistor R2 is grounded.

[0023] 3. Since the voltage division of the measured resistor Rt is small, the accuracy of direct ADC acquisition is low, so an instrument amplifier is added before ADC acquisition to improve the ADC acquisition accuracy;

[0024] 4. Use a voltage divider circuit to adjust the voltage value across the measured resistor Rt through the instrument amplifier to the middle of the ADC acquisition range, which is beneficial to the accuracy of the voltage acquisition;

[0025] 5.ADC acquisition uses the 12-bit ADC channel inside the STM32F4 to measure the voltage of the circuit, and then calculates its resistance value based on the resistance measurement principle.

[0026] Its components include Figure 1 As shown, it consists of STM32F4, instrumentation amplifier, and voltage-dividing resistor measurement circuit. The voltages Vh and Vl at the acquisition points are input into the instrumentation amplifier to be amplified by a certain multiple M, and then the voltage Vout amplified by the instrumentation amplifier is acquired through the ADC channel of STM32F4, where Vout / M=Vh-Vl, R1 and R2 are 49.9 ohms, and the corresponding channel resistance value is calculated by principle.

[0027] The voltage divider circuit has a self-test resistor Ri. When the system is initially running, connect Ri, collect the voltage and calculate its measured value, then compare it with the real value to verify that the circuit functions normally and complete the circuit self-test. The voltage divider principle obtains the Ri calculation formula as follows: After self-test, the voltage divider circuit is connected to the resistance to be measured (current limiting protection resistance) Rt for measurement. Similarly, the calculation formula of Rt is:

[0028] As a preferred implementation of this embodiment, the ADC channel of STM32F4 is configured to have 12-bit precision, the sampling period is configured to be 20 periods, the conversion period is set to be 88 clock periods, and the ADC data is collected ten times to obtain the average value.

[0029] The principle of resistance measurement circuit is as follows Figure 2 As shown, the measured resistor Rt is connected in series with two precision resistors R1 and R2 (one thousandth error), and the ADC channel is connected to Vh and Vl. Then, the principle of voltage division is analyzed. According to the formula Calculate the resistance Rt to be measured.

[0030] The value of R1 and R2 is 49.9 ohms, so that the collected values ​​of Vh and Vl are between the ADC thresholds, and values ​​close to V_Power (power supply) or 0 will not be collected, avoiding the collection of boundary data and ensuring the accuracy of the data.

[0031] It can be seen from the resistance measurement circuit schematic that when the collected voltage is close to V_Power×M, the measured resistor Rt is open-circuited, and its measurement result will be close to infinity (under normal circumstances, the resistance value is about 3 ohms), and the measured resistor Rt is non-conductive.

Claims

1. A high-precision current-limiting resistor measurement circuit, comprising a resistor to be measured, an instrument amplifier, and an ADC, characterized in that: It also includes a voltage divider circuit, which includes a resistor R1 and a resistor R2. The resistors R1 and R2 are respectively connected in series at both ends of the measured resistor, the other end of the resistor R1 is connected to the power supply, and the other end of the resistor R2 is grounded; the two ends of the measured resistor are connected to the ADC through an instrument amplifier, so that the voltage value at both ends is adjusted to the middle of the ADC acquisition range.

2. The high-precision current-limiting resistor measurement circuit according to claim 1, characterized in that: The voltage divider circuit also includes a self-detection resistor, which is connected in parallel with the resistor to be measured, and whose two ends are respectively connected in series with the resistor R1 and the resistor R2.

3. The high-precision current-limiting resistor measurement circuit according to claim 2, characterized in that: Switches are provided between the self-detection resistor and the resistor R1 and between the resistor to be measured and the resistor R1, and the switches are used to connect the voltage divider circuits respectively.

4. The high-precision current-limiting resistor measurement circuit according to claim 1 or 2, characterized in that: The resistance values ​​of resistor R1 and resistor R2 are equal.

5. The high-precision current-limiting resistor measurement circuit according to claim 4, characterized in that: The values ​​of resistors R1 and R2 are 49.9 ohms.

6. The high-precision current-limiting resistor measurement circuit according to claim 1, characterized in that: The ADC uses STM32F4 as the main control, which has a 12-bit high-precision ADC module and 24 channels.

7. The high-precision current-limiting resistor measurement circuit according to claim 1 or 6, characterized in that: The ADC sampling period is configured as 20 cycles, the conversion period is set to 88 clock cycles, and the ADC data is collected ten times to take the average value.

8. A high-precision current-limiting resistor measurement method, using a high-precision current-limiting resistor measurement circuit with a self-checking resistor, characterized in that: The following steps are involved: (1) When the system is initially running, the self-test resistor Ri is connected. After amplification by the instrumentation amplifier, the ADC collects the voltage and calculates its measured value, which is then compared with the true value to verify that the circuit functions normally and complete the circuit self-test; (2) After self-test, the voltage divider circuit is connected to the resistance Rt to be measured.

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