Detailed explanation of high resistance measurement circuit principle, design and application

In the field of electronic measurement, high-resistance measurement circuits are a type of key technology used to measure high-impedance components or circuits. With the miniaturization and high-precision requirements of electronic devices, accurate measurement of high resistance values ​​has become particularly important. This article will comprehensively introduce the principles, design points and practical applications of high-resistance measurement circuits to help readers gain an in-depth understanding of this technical field.

High-resistance measurement circuits are mainly used to measure resistance values ​​of hundreds of megohms or even higher.resistanceor circuit input impedance. Due to the presence of high resistance, traditional measurement methods are easily affected by environmental interference and the input impedance of the instrument itself, resulting in measurement errors. High resistance measurement circuits usually use high input impedance amplifiers and special measurement techniques to ensure measurement accuracy and stability.

The core of the high-resistance measurement circuit is to reduce the loading effect of the measurement system on the component under test. By using operational amplifiers with field effect transistor (FET) inputs, the input impedance can reach over several thousand megaohms, thereby avoiding current drain during measurements. At the same time, the voltage follower structure is adopted to effectively isolate the measured object from the measuring instrument and ensure the integrity of the measurement signal.

When designing a high-impedance measurement circuit, it is crucial to select an op amp with low leakage current and high input impedance. For example, JFET or CMOS input op amps can provide very low input bias current. In addition, the circuit layout should pay attention to reducing stray capacitance and leakage paths, and use high-quality insulation materials and protective measures to avoid environmental humidity and dust from affecting the measurement results.

Since high-resistance measurement circuits are extremely sensitive to tiny currents, electromagnetic interference and electrostatic interference can easily lead to measurement errors. Commonly used anti-interference measures include shielded metal casings, twisted pair transmission lines, filter circuits and reasonable grounding designs. In addition, changes in ambient temperature will also affect the measurement results, which need to be corrected through a temperature compensation circuit or software algorithm.

In order to ensure measurement accuracy, it is very important to calibrate the high-resistance measurement circuit regularly. Calibration usually uses standard high-value resistors or bridges for comparison testing. Eliminate system errors by adjusting circuit parameters or software compensation. In addition, the introduction of automatic calibration function improves the reliability of measurement and ease of operation.

High-resistance measurement circuits are widely used in insulation resistance testing, electrostatic measurement, bioelectrical signal acquisition, and material resistivity measurement. In power systems, it is used to detect the performance of insulating materials; in medical equipment, it is used to collect weak electrical signals from the human body; in the field of scientific research, it is used to measure the electrical properties of high-resistance materials.

With the development of nanotechnology and new materials, high-resistance measurement circuits are facing the challenge of higher measurement accuracy and smaller size. Integrated, high-sensitivity, multi-functional high-resistance measurement modules will become a trend. At the same time, the combination of intelligent and digital technologies will greatly improve measurement efficiency and data processing capabilities.

As an important part of electronic measurement, high-resistance measurement circuits achieve accurate measurement of high-resistance components by virtue of their high input impedance and anti-interference capabilities. Through reasonable device selection, scientific circuit design and effective calibration methods, the accuracy and reliability of measurement can be significantly improved. In the future, with the continuous advancement of technology, high-resistance measurement circuits will show broad application prospects in more fields. Mastering the core technology of high-resistance measurement circuits is of great significance to electronic engineers and scientific researchers.