A micro-resistance measurement device and method using fixed small current excitation

Abstract

The embodiment of the present application provides a micro-resistance measurement device and method using a fixed small current excitation, and relates to the field of electronic measurement technology. The method includes: a current sampling circuit, which obtains a first voltage signal; the first voltage signal is generated at both ends of the known resistor after the constant current passes through the known resistor; a voltage sampling circuit, which obtains a second voltage signal; the second voltage signal is generated at both ends of the resistor to be measured after the constant current passes through the resistor to be measured; a processor, which records the resistance value of the known resistor, converts the first voltage signal into a first current signal, and calculates the resistance value of the resistor to be measured based on the collected first current signal and the second voltage signal. The device uses a fixed small current excitation of 10mA, which can achieve accurate measurement of mΩ-level resistance, can be used for micro-resistance measurement in dangerous scenes such as flammable and explosive, and has good environmental applicability.

Description

Technical Field

[0001] The present application relates to the field of electronic measurement technology, and in particular to a micro-resistance measurement device and method using fixed small current excitation. Background Art

[0002] Resistance measurement has application requirements in different scenarios. Commonly used measurement methods include constant current source method, bridge method, resistance comparison method, etc. In some flammable and explosive scenarios, in order to ensure safety, there are often strict requirements on the test current, such as the measurement of the on-resistance of the cable on the bomb and the internal resistance of the detonator. When using small current excitation to measure micro-resistance, the sampling voltage is very small, which brings certain difficulties to the accurate test of resistance.

[0003] At present, resistance testing solutions usually use small currents to measure larger resistances, and larger currents to test very small resistances, to ensure that the sampled voltage can be accurately collected, so as to calculate the accurate resistance value. When the existing technology tests mΩ-level resistors, the test current is usually greater than 50mA, which is feasible for testing the on-resistance of devices such as relays and circuit breakers without damaging the devices. However, for some scenarios with more stringent requirements on test currents, such as flammable and explosive scenarios (currents above 30mA are dangerous for some scenarios), it is still difficult to meet the requirements. Summary of the invention

[0004] The embodiment of the present application provides a micro-resistance measurement device and method using a fixed small current excitation. It uses a fixed small current excitation of 10mA to achieve accurate measurement of mΩ-level resistance, can be used for micro-resistance measurement in flammable, explosive and other dangerous scenarios, and has good environmental applicability.

[0005] The embodiments of the present application are implemented in the following manner:

[0006] A micro-resistance measuring device using fixed small current excitation includes: a current sampling circuit to obtain a first voltage signal; the first voltage signal is generated at both ends of the known resistor after the constant current passes through the known resistor; a voltage sampling circuit to obtain a second voltage signal; the second voltage signal is generated at both ends of the resistor to be measured after the constant current passes through the resistor to be measured; a processor to convert the first voltage signal into a first current signal according to the resistance value of the known resistor; and calculate the resistance value of the resistor to be measured according to the collected first current signal and the second voltage signal. This solution uses fixed small current excitation to achieve accurate measurement of mΩ-level resistance. And the real-time use of current and voltage dual parameters can eliminate the constant current source current error and improve the measurement accuracy of the device compared to the general voltage single parameter sampling test circuit.

[0007] Preferably, the current sampling circuit includes a first amplifier and a first converter; the known resistor, the first amplifier, the first converter and the processor are sequentially connected in series. The method sequentially performs voltage amplification and digital-to-analog conversion on the first voltage signal to make the sampling value more accurate.

[0008] Preferably, the voltage sampling circuit includes a second amplifier and a second converter; the unknown resistor, the second amplifier, the second converter and the processor are sequentially connected in series. Similarly, the method sequentially performs voltage amplification and digital-to-analog conversion on the second voltage signal to make the sampling value more accurate.

[0009] Preferably, the device is also provided with a current limiting unit located between the known resistor and the unknown resistor; the current limiting unit limits the constant current before the constant current passes through the resistor to be measured; the constant current provides an energy signal for the resistor to be measured, and the current limiting resistor ensures that the current passing through the resistor to be measured is not greater than a certain threshold, such as 30mA. By taking current limiting measures for the constant current, the maximum test current can be limited, so that the device can be used for micro-resistance measurement in dangerous scenes such as flammable and explosive materials, and has good environmental adaptability;

[0010] Preferably, a first follower is provided between the first amplifier and the known resistor; a second follower is provided between the second amplifier and the resistor to be measured. In this solution, the follower mainly performs a voltage following function to isolate the first voltage signal and the second voltage signal to reduce mutual interference between the two.

[0011] Preferably, the device further comprises a temperature sensor connected to the processor; the processor receives the real-time ambient temperature parameter provided by the temperature sensor and automatically performs temperature compensation. This solution uses a temperature sensor to measure the ambient temperature and provides it to the processor for automatic temperature compensation, thereby improving the error caused by temperature drift of components and further ensuring that the device has good environmental adaptability.

[0012] Preferably, the device further comprises a voltage reference source, connected to the first and second converters respectively; the converter automatically performs voltage correction according to the reference voltage provided by the voltage reference source. This solution can meet the requirements of accurate voltage sampling under low current excitation conditions.

[0013] A micro-resistance measurement method using a fixed small current excitation includes: using a current sampling circuit to obtain a first voltage signal; the first voltage signal is generated at both ends of the known resistor after the constant current passes through the known resistor; using a voltage sampling circuit to obtain a second voltage signal; the second voltage signal is generated at both ends of the resistor to be measured after the constant current passes through the resistor to be measured; a processor converts the first voltage signal into a first current signal according to the resistance value of the known resistor, and calculates the resistance value of the resistor to be measured according to the collected first current signal and the second voltage signal. .

[0014] Preferably, the current limiting unit further includes limiting the constant current before the constant current passes through the resistor to be measured; the constant current provides an energy signal for the resistor to be measured. The current limiting circuit ensures that the current passing through the resistor to be measured is not greater than a certain threshold, such as 30mA.

[0015] Preferably, the processor is connected to a temperature sensor; and temperature compensation is automatically performed by receiving real-time ambient temperature parameters provided by the temperature sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 A schematic diagram of a measuring device provided in an embodiment of the present application;

[0018] Icons: 1-constant current source; 2-known resistance; 3-current limiting unit; 4-current sampling circuit; 41-first amplifier; 42-first converter; 4-first follower; 5-voltage sampling circuit; 51-second amplifier; 52-second converter; 53 second follower; 6-processor; 7-temperature sensor; 8-voltage reference source; 9-display screen. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present application will be described below in conjunction with the accompanying drawings in the embodiments of the present application.

[0020] Related Notes:

[0021] 1. The device is equipped with a power module for AC / DC conversion, which converts 220V AC power into DC power to provide power for the entire measuring device.

[0022] 2. The first and second amplifiers and the first and second converters are both made of high-precision devices. The amplification factor of the first and second amplifiers is preferably about 500 times, and the first and second converters are made of digital-to-analog conversion devices with more than 24 bits.

[0023] 3. Constant current is generated by a constant current source. The resistance value of a known resistor is known.

[0024] The present invention provides a micro-resistance measuring device using fixed small current excitation, comprising:

[0025] The current sampling circuit 4 acquires a first voltage signal; the first voltage signal is generated at both ends of the known resistor after the constant current passes through the known resistor 2;

[0026] A voltage sampling circuit 5 is used to obtain a second voltage signal; the second voltage signal is generated at both ends of the resistor to be measured after the constant current passes through the resistor to be measured;

[0027] The processor 6 records the resistance value of the known resistor 2, converts the first voltage signal into a first current signal, and calculates the resistance value of the resistor to be measured according to the collected first current signal and the second voltage signal.

[0028] Example 1: Please refer to Figure 1 In the embodiment of the present invention, the specific connection relationship is: after the power supply end of the constant current source 1 is connected through the known resistor 2, after forming a loop with the resistor to be measured, it returns to the other power supply end of the constant current source, that is, the constant current source simultaneously provides energy to the known resistor and the resistor to be measured. A loop is formed with the constant current source through a 4-port measuring probe. The other two ports of the 4-port are connected to the voltage sampling circuit to provide the voltage sampling circuit with the voltage value of the resistor to be measured. Among them, the measuring probe adopts a 4-wire probe to eliminate the resistance influence of the probe connection. The ① line end of the 4-wire measuring probe is connected to the output end of the current limiting unit 31 as the current input end of the resistor to be measured, and the ④ line end is directly connected to the constant current source 1 as the current output end of the resistor to be measured, thereby forming a current loop and generating a voltage at both ends of the resistor to be measured. The ② and ③ line ends are used to measure the voltage value at both ends of the resistor to be measured. The current sampling circuit 4 includes a first amplifier 41 and a first converter 42, wherein the first amplifier 41, the first converter 42 and the processor 6 are cascaded in sequence. The current sampling circuit 4 is connected in parallel with the known resistor 2, so as to measure the voltage value across the known resistor.

[0029] The principle of the whole working process is as follows: the constant current source 1 generates a constant current. In this embodiment, the constant current is 10mA, which is converted into a first voltage signal through the known resistor 2. In this embodiment, the known resistor 2 adopts a high-precision resistor. The current sampling circuit 4 collects the first voltage signal at both ends of the known resistor 2, passes through the first amplifier 41 and the first converter 42 in sequence, performs voltage amplification and digital-to-analog conversion in sequence, and finally converts it into a digital signal and enters the processor 6 for subsequent processing. In addition, after the constant current passes through the resistor to be measured, a second voltage signal is generated at both ends of the resistor to be measured; the second voltage signal is obtained through the voltage sampling circuit 5. The processor 6 records the resistance value of the known resistor 2. According to Ohm's law, the first voltage signal can be converted into a first current signal, and then the resistance value of the resistor to be measured is calculated again according to Ohm's law based on the collected first current signal and the second voltage signal.

[0030] Example 2: Based on Example 1, please continue to refer to Figure 1 The voltage sampling circuit 5 also includes a second amplifier 51 and a second converter 52, wherein the second amplifier 51, the second converter 52 and the processor 6 are cascaded in sequence. The constant current source 1 generates a constant current of 10mA through the resistor to be measured, and generates a second voltage signal at both ends of the circuit to be measured. The voltage sampling circuit 5 also includes a second amplifier 51 and a second converter 52. After the second voltage signal enters the voltage sampling circuit 5, it passes through the second amplifier 51 and the second converter 52, and is sequentially amplified and converted into digital-to-analog conversion, and finally converted into a digital signal and enters the processor 6 for subsequent processing.

[0031] Example 3: Based on Example 1 and 2, please continue to refer to Figure 1 , the device also includes the current limiting unit, which limits the constant current before the constant current passes through the resistor to be measured; the constant current provides an energy signal for the resistor to be measured; in the embodiment of the present invention, the current limiting unit 31 uses a fuse with a 30mA fusing parameter, and before the constant current passes through the resistor to be measured, the current limiting unit 31 limits the constant current to ensure that the current passing through the resistor to be measured is not greater than 30mA. Due to the current limiting measures taken, the device can be used for micro-resistance measurement in dangerous scenes such as flammable and explosive, and has good environmental applicability.

[0032] Example 4: Based on Examples 1 to 3, please continue to refer to Figure 1, a first follower 43 is provided between the first amplifier 41 and the known resistor 2; a second follower 53 is provided between the second amplifier 51 and the resistor to be measured. The first and second followers serve as the intermediate isolation stage of the circuit, and play the role of voltage following after the voltage is input, thereby ensuring the isolation of the two voltages in the current sampling circuit 4 and the voltage sampling circuit 5, and reducing the interference formed between them. It should be noted that the ② and ③ two-wire ends of the 4-wire measurement probe are connected to the input end of the second follower 53, so that the voltage sampling circuit 5 can prepare to collect the voltage value at both ends of the resistor to be measured.

[0033] Example 5: Based on Examples 1 to 4, please continue to refer to Figure 1 In this embodiment, the device further includes a temperature sensor 5, which is directly connected to the processor 6; the temperature sensor 5 measures the ambient temperature, records the ambient parameters and sends them to the processor 6. After receiving the real-time ambient temperature parameters provided by the temperature sensor 5, the processor 6 automatically performs temperature compensation through the temperature compensation circuit. This improves the error caused by the temperature drift of components and improves the measurement accuracy.

[0034] Example 6: Based on Examples 1 to 5, please continue to refer to Figure 1 In this embodiment, the device further includes a voltage reference source 6, which is also a high-precision device and is connected to the first converter 42 and the second converter 52. The voltage reference source 6 provides a reference voltage for the first converter 42 and the second converter 52, respectively. The converter automatically performs voltage correction according to the reference voltage, which can further improve the accuracy of voltage sampling.

[0035] Example 7: Based on Examples 1 to 6, please continue to refer to Figure 1 In this embodiment, the device also includes a display screen 7, which is connected to the processor 6 and can directly display the test results such as the voltage value collected by the two sampling circuits and the resistance value of the resistor to be measured on the display screen for easy observation.

[0036] The above description is only an embodiment of the present application and is not intended to limit the scope of protection of the present application. For those skilled in the art, the present application may have various changes and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present application. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings.

[0037] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

[0038] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

Claims

1. A micro-resistance measurement method using fixed small current excitation, characterized in that: The method includes: A first voltage signal is obtained by using a current sampling circuit; the first voltage signal is generated at both ends of a known resistor after a constant current passes through the known resistor; A second voltage signal is obtained by using a voltage sampling circuit; the second voltage signal is generated at both ends of the resistor to be measured after a constant current passes through the resistor to be measured; The processor converts the first voltage signal into a first current signal according to the resistance value of the known resistor, and calculates the resistance value of the resistor to be measured according to the collected first current signal and the second voltage signal; The micro-resistance measurement device using fixed small current excitation includes: A current sampling circuit is used to obtain a first voltage signal; the first voltage signal is generated at both ends of a known resistor after a constant current passes through the known resistor; A voltage sampling circuit is used to obtain a second voltage signal; the second voltage signal is generated at both ends of the resistor to be measured after a constant current passes through the resistor to be measured; The processor converts the first voltage signal into a first current signal according to the resistance value of the known resistor; and calculates the resistance value of the resistor to be measured according to the collected first current signal and the second voltage signal; The current sampling circuit includes a first amplifier and a first converter; a known resistor, a first amplifier, a first converter and a processor are connected in series in sequence; The voltage sampling circuit includes a second amplifier and a second converter; the unknown resistor, the second amplifier, the second converter and the processor are connected in series in sequence; A current limiting unit is also provided between the known resistor and the unknown resistor; the current limiting unit limits the constant current before the constant current passes through the resistor to be measured; the constant current provides an energy signal for the resistor to be measured; A first follower is provided between the first amplifier and the known resistor; a second follower is provided between the second amplifier and the resistor to be measured; The device also includes a temperature sensor connected to the processor; The device also includes a voltage reference source connected to the first and second converters respectively; the first and second converters automatically perform voltage correction according to the reference voltage provided by the voltage reference source.

2. A micro-resistance measurement method using fixed small current excitation as claimed in claim 1, characterized in that The current limiting unit further includes limiting the constant current before the constant current passes through the resistor to be measured; The constant current provides an energy signal to the resistor to be measured.

3. A micro-resistance measurement method using fixed small current excitation as claimed in claim 1 or 2, characterized in that The processor is connected to the temperature sensor.

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