A drive system for improving the linearity of AC micro-resistance measurement circuits

Abstract

This invention provides a drive system for improving the linearity of AC micro-resistance measurement circuits. Based on the voltage value sampled by the ADC module, the amplification ratio coefficients of the magnetic induction coils corresponding to the measured resistor Rx and the standard resistor Rs are adjusted. The coils are adjusted to the optimal amplification ratio range, ensuring that the difference between the first and second amplified voltages is less than a set threshold. This improves the measurement linearity of micro AC signals across the entire measurement range. Furthermore, based on the characteristics of a sinusoidal AC constant current source, this invention designs a two-stage proportionally adjustable magnetic induction coil. The difference in amplified voltages between the measured resistor Rx and the standard resistor Rs is amplified through the second-stage coil, i.e., the third coil. This improves the stability of the amplification coefficient of micro AC signals across the entire measurement range, making it particularly suitable for high-precision resistance measurement and resistance-type instrument testing and calibration. It also improves the measurement accuracy of standard platinum resistance thermometers, meeting the measurement requirements of AC micro-resistance measuring instruments.

Description

Technical Field

[0001] This invention belongs to the field of precision testing, and in particular relates to a drive system for improving the linearity of AC micro-resistance measurement circuits. Background Technology

[0002] Resistance, as a fundamental physical quantity in electrical measurement, is involved in all aspects of the national economy, scientific research, national defense, and industrial production. It plays a crucial role in scientific research, production, and daily life, and obtaining resistance values ​​quickly and accurately is of great significance. With the advancement of science and technology, the application of many new disciplines and technologies relies heavily on the precise measurement of resistance. For example, in materials science, the electrical properties of many metals change with temperature, and the changes in most of these electrical properties are closely related to changes in resistance. Therefore, the precise measurement of minute resistances can provide strong theoretical support for the study of the properties of such materials. In the field of temperature measurement, standard platinum resistance thermometers are commonly used for precision temperature measurement. Temperature is often acquired by precisely measuring the resistance of these sensors, such as the FLUKE 15XX series from the United States, the GLOK 6622 series from Canada, and other similar sensors. High-end precision thermometers used in the market, such as the MI6010 series and the British ASLF500, all employ the principle of high-precision resistance measurement. In the aerospace and defense industries, during routine maintenance of missile vehicles, it is necessary to measure the resistance of components such as pyrotechnics, relays, and switches in the equipment circuits to understand the quantitative changes in the equipment. For example, the performance and reliability of pyrotechnics play a crucial role in whether the aircraft can operate normally. Pyrotechnic testing is an important part of the aircraft's self-inspection and routine testing. It is necessary to periodically and accurately measure the change curve of the resistance value of the pyrotechnics without power to determine whether the performance of the pyrotechnics is intact.

[0003] In recent years, with the enhancement of my country's comprehensive national strength, the number of precision instruments used in basic science, industrial production, and national defense has also increased. Significant achievements have been made in the field of high-precision resistance measurement. However, facing the demands of new scientific research, resistance measurement remains a particularly challenging topic. Especially when the resistance being measured is small, the contact resistance and wire resistance in the measurement circuit can introduce significant interference errors, severely impacting the accurate measurement of minute resistances. Simultaneously, when the resistance being measured is extremely small, the signal detected in the circuit will be very weak and easily drowned out by circuit noise, greatly affecting measurement accuracy. Furthermore, using a large current to drive the minute resistor in the test circuit can easily damage the resistor, and as the measurement time increases, the measured resistor will experience temperature changes due to the excessive circuit current, leading to a certain degree of loss in measurement accuracy. Therefore, developing a high-precision minute resistance measurement circuit under low-current driving conditions is imperative. It is necessary to propose the development of a high-precision minute resistance tester, and through the development of this standard device, commercialize it to meet the key metrological needs of project construction and research support conditions in various scientific research and production fields in my country.

[0004] To reduce the impact of temperature on the measurement accuracy of AC micro-resistance measurement circuits, the drive current of the measurement circuit is typically no more than 1mA. Furthermore, due to the small resistance value of the resistor being measured, the required measurement accuracy for the test circuit within the 0–120Ω range is ±0.0002Ω. Common resistance measurement methods cannot meet these technical requirements. Therefore, there is an urgent need to research a drive circuit that improves the linearity of AC micro-resistance measurement circuits to meet the measurement needs of high-precision micro-resistance devices. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a driving system for improving the linearity of AC micro-resistance measurement circuits. Based on the sampling data from the ADC module, the amplification ratio coefficients of the magnetic induction coils corresponding to the resistor under test Rx and the standard resistor Rs are adjusted to improve the linearity of the amplification coefficient of the micro AC signal across the entire measurement range.

[0006] A driving system for improving the linearity of an AC micro-resistance measurement circuit includes a sinusoidal AC constant current source, a first coil X, a second coil S, a third coil, a switch array I, a switch array II, an operational amplifier, an ADC module, and a standard resistor Rs. The sinusoidal AC constant current source is connected in series with the resistor to be measured Rx and the standard resistor Rs and then grounded. Simultaneously, the standard resistor Rs is connected to the primary coil of the second coil S via switch array II, and the resistor to be measured Rx is connected to the primary coil of the first coil X via switch array I.

[0007] One end of the primary coil of the third coil is connected to the first amplified voltage of the resistor Rx to be measured, output by the secondary coil of the first coil X, and the other end is connected to the second amplified voltage of the standard resistor Rs, output by the secondary coil of the second coil S. The difference amplified signal between the first and second amplified voltages is then output by the secondary coil of the third coil. The difference amplified signal is connected to the non-inverting input of the operational amplifier, so that the operational amplifier isolates and follows the difference amplified signal. The ADC module samples the isolated following voltage signal output by the operational amplifier. Based on the sampled voltage value, a switch is selected from switch array I and switch array II to be turned on, so that the difference between the first and second amplified voltages is less than a set threshold.

[0008] Furthermore, a drive system for improving the linearity of an AC micro-resistance measurement circuit also includes a processing module;

[0009] The processing module is used to receive the sampled voltage value output by the ADC module, and turn on one of the switches in switch array I and switch array II respectively according to the sampled voltage value, thereby adjusting the amplification ratio coefficient of the first coil X and the second coil S, so that the difference between the first amplified voltage and the second amplified voltage is less than a set threshold.

[0010] Furthermore, the testers manually turned on one switch from switch array I and switch array II based on the sampled voltage value, thereby adjusting the amplification ratio coefficients of the first coil X and the second coil S, so that the difference between the first amplified voltage and the second amplified voltage is less than a set threshold.

[0011] Furthermore, copper terminals and connecting wires are used to connect the resistor under test Rx and the standard resistor Rs to the drive system.

[0012] Furthermore, the operational amplifier is a high input impedance operational amplifier.

[0013] Furthermore, the effective value of the sinusoidal AC constant current source is 1mA.

[0014] Beneficial effects:

[0015] 1. This invention provides a drive system for improving the linearity of AC micro-resistance measurement circuits. Based on the voltage value sampled by the ADC module, the amplification ratio coefficients of the magnetic induction coils corresponding to the measured resistor Rx and the standard resistor Rs are adjusted. The coils are adjusted to the optimal amplification ratio range, ensuring that the difference between the first and second amplified voltages is less than a set threshold. This improves the linearity of the measurement of micro-AC signals across the entire range, significantly enhancing the measurement accuracy of the equipment. Furthermore, based on the characteristics of a sinusoidal AC constant current source, this invention designs a two-stage proportionally adjustable magnetic induction coil. The difference in amplified voltage between the measured resistor Rx and the standard resistor Rs is amplified through the second-stage coil, i.e., the third coil. This improves the stability of the amplification coefficient of micro-AC signals across the entire range, making it particularly suitable for high-precision resistance measurement and resistance-type instrument testing and calibration. It also improves the measurement accuracy of standard platinum resistance thermometers, meeting the measurement requirements of AC micro-resistance measuring instruments.

[0016] 2. This invention provides a drive system for improving the linearity of AC micro-resistance measurement circuits. By using terminals made of low thermoelectric potential materials such as copper and connecting wires made of copper to connect the resistor to be measured Rx and the standard reference resistor Rs to the drive system, the influence of thermoelectric potential on the linearity of the resistance temperature measuring instrument can be reduced.

[0017] 3. This invention provides a driving system for improving the linearity of AC micro-resistance measurement circuits. It uses a high input impedance operational amplifier to isolate and follow the output voltage of coil XS, which can improve the circuit driving capability and reduce the influence of circuit load on the amplification ratio of the magnetic induction coil.

[0018] 4. This invention provides a drive system for improving the linearity of AC micro-resistance measurement circuits. The effective value of the AC constant current source is controlled at around 1mA, which can reduce the influence of thermal noise on the linearity of the resistance temperature measuring instrument under test. This enables accurate measurement of small resistance values ​​within the range of 0 to 120Ω, and thus can be widely used in precision temperature measuring instruments such as AC platinum resistance temperature measuring instruments. Attached Figure Description

[0019] Figure 1 The present invention provides a principle block diagram of a drive system for improving the linearity of an AC micro-resistance measurement circuit. Detailed Implementation

[0020] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings.

[0021] The working principle of the AC micro-resistance measurement circuit is mainly to use an AC constant current source as a driving circuit to complete the acquisition of the micro-resistance value and compare it with a standard resistor to calculate the resistance value of the resistor to be measured. Specifically, the resistance to be measured can be calculated by using the resistance value of the standard resistor and the amplification ratio coefficient of the two coils.

[0022] To address the measurement requirements of AC micro-resistance measurement circuits, and with the aim of suppressing thermoelectric potential errors and system noise interference to improve the linearity of circuit measurements, such as... Figure 1 As shown, the present invention provides a driving system for improving the linearity of an AC micro-resistance measurement circuit, including a sinusoidal AC constant current source with an effective value of 1mA, a first coil X, a second coil S, a third coil, a switch array I, a switch array II, an operational amplifier, an ADC module, and a standard resistor Rs; wherein, the sinusoidal AC constant current source is connected in series with the resistor to be measured Rx and the standard resistor Rs and then grounded, and the standard resistor Rs is connected to the primary coil of the second coil S through the switch array II, and the resistor to be measured Rx is connected to the primary coil of the first coil X through the switch array I;

[0023] One end of the primary coil of the third coil is connected to the first amplified voltage of the resistor Rx to be measured, output by the secondary coil of the first coil X, and the other end is connected to the second amplified voltage of the standard resistor Rs, output by the secondary coil of the second coil S. The difference amplified signal between the first and second amplified voltages is then output by the secondary coil of the third coil. The difference amplified signal is connected to the non-inverting input of the operational amplifier, so that the operational amplifier isolates and follows the difference amplified signal. The ADC module samples the isolated following voltage signal output by the operational amplifier. Based on the sampled voltage value, a switch is selected from switch array I and switch array II to be turned on, so that the difference between the first and second amplified voltages is less than a set threshold, that is, the difference approaches 0. At the same time, a difference of 0 between the first and second amplified voltages is an ideal case.

[0024] It should be noted that when turning on the switches in switch array I and switch array II based on the sampled voltage value, a processing module can be set up. This processing module receives the sampled voltage value output by the ADC module and then turns on one switch from switch array I and switch array II respectively based on the sampled voltage value. This adjusts the amplification ratio coefficients of the first coil X and the second coil S, ensuring that the difference between the first amplified voltage and the second amplified voltage is less than a set threshold. Alternatively, the test personnel can manually interpret the sampled voltage value and then manually turn on one switch from switch array I and switch array II respectively based on the sampled voltage value. This adjusts the amplification ratio coefficients of the first coil X and the second coil S, ensuring that the difference between the first amplified voltage and the second amplified voltage is less than a set threshold.

[0025] It should be noted that the 1mA sinusoidal AC constant current source has high stability in phase and amplitude, which can reduce the impact of thermal noise on the linearity of the platinum resistance thermometer. A high-precision AC standard resistor Rs is selected to reduce the inductance distribution parameters introduced by the standard resistor. The first coil X and the second coil S are proportionally adjustable magnetic induction coils. By selecting different switches on the switch array to conduct, the amplification ratio coefficients of the magnetic induction coils corresponding to the resistor under test Rx and the standard resistor Rs are adjusted, ensuring that the difference between the first amplified voltage and the second amplified voltage is less than a set threshold, thus improving the linearity of the amplification coefficient of small AC signals across the entire measurement range. Figure 1 The connection relationship is such that terminals made of low thermoelectric potential materials such as copper and copper connecting wires are used to connect the resistor to be measured Rx and the standard resistor Rs into the drive circuit, so as to reduce the influence of thermoelectric potential on the linearity of the measurement of the platinum resistance thermometer. The resistor to be measured Rx can be a platinum resistance thermometer. The corresponding switch array can be initialized according to the sampling voltage of the resistor to be measured Rx and the standard resistor Rs to control the amplification ratio coefficient of the magnetic induction coil.

[0026] In summary, based on the analysis of the requirements for measuring the resistance value of small resistors, this invention employs sinusoidal AC constant current source driving technology, which can effectively suppress the thermoelectric potential in the AC small resistance measurement circuit. Under the condition of 1mA driving current, by adjusting the proportional coefficient of the magnetic induction coil, the linearity of the amplification factor of the driving circuit can be improved across the entire range, effectively improving the measurement accuracy of the AC small resistance measurement circuit. Simultaneously, the sinusoidal AC constant current source driving circuit can also effectively suppress thermoelectric potential errors and system noise interference. Furthermore, the small resistance measurement circuit based on sinusoidal AC constant current source driving also has certain advantages in terms of anti-interference and long-term stability. Under the condition of 1mA AC constant current source driving circuit, it can accurately measure small resistance values ​​within the range of 0–120Ω, and can be widely applied to precision temperature measuring instruments such as AC platinum resistance thermometers, effectively suppressing thermoelectric potential errors and system noise interference in the equipment, greatly improving the measurement accuracy of the equipment.

[0027] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.

Claims

1. A drive system for improving the linearity of an AC micro-resistance measurement circuit, characterized in that, The apparatus comprises a sinusoidal AC constant current source, a first coil X, a second coil S, a third coil, a switch array I, a switch array II, an operational amplifier, an ADC module, and a standard resistor Rs; wherein the sinusoidal AC constant current source is connected in series with the standard resistor Rs and the to-be-measured resistor Rx, and grounded, and meanwhile, the standard resistor Rs is connected to the primary coil of the second coil S through the switch array II, and the to-be-measured resistor Rx is connected to the primary coil of the first coil X through the switch array I. One end of the primary coil of the third coil is connected to the first amplified voltage of the to-be-measured resistor Rx output by the secondary coil of the first coil X, and the other end is connected to the second amplified voltage of the standard resistor Rs output by the secondary coil of the second coil S, and the difference between the first amplified voltage and the second amplified voltage is output by the secondary coil of the third coil; the difference amplified signal is connected to the non-inverting input terminal of the operational amplifier, so that the operational amplifier isolates and follows the difference amplified signal; the ADC module samples the isolated and followed voltage signal output by the operational amplifier; according to the sampling voltage value, one switch in the switch array I and the switch array II is selected to be turned on, so that the difference between the first amplified voltage and the second amplified voltage is less than a set threshold.

2. The driving system for improving the linearity of an AC micro- resistance measurement loop according to claim 1, wherein The apparatus further comprises a processing module. The processing module is configured to receive the sampling voltage value output by the ADC module, and according to the sampling voltage value, one switch in the switch array I and the switch array II is turned on, so as to adjust the amplification ratio of the first coil X and the second coil S, and make the difference between the first amplified voltage and the second amplified voltage less than the set threshold.

3. The drive system for improving the linearity of an AC micro- resistance measurement circuit according to claim 1, wherein The tester selects one switch in the switch array I and the switch array II according to the sampling voltage value and turns on the switch manually, so as to adjust the amplification ratio of the first coil X and the second coil S, and make the difference between the first amplified voltage and the second amplified voltage less than the set threshold.

4. The drive system for improving the linearity of an AC micro- resistance measurement circuit according to claim 1, wherein The to-be-measured resistor Rx and the standard resistor Rs are connected to the driving system through the wire terminals and the connecting wires made of red copper.

5. A driving system for improving the linearity of an AC micro- resistance measurement circuit according to any one of claims 1 to 4, characterized in that, The operational amplifier is a high input impedance operational amplifier.

6. A driving system for improving the linearity of an AC micro- resistance measurement circuit according to any one of claims 1 to 4, characterized in that, The effective value of the sinusoidal AC constant current source is 1 mA.

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