Comprehensive analysis of high value resistance measurements

Electronic engineering and precision testing fields, high resistanceresistanceThe measurement has always been a technical problem. Due to its very large resistance, traditional measurement methods are often difficult to ensure accuracy and stability. Therefore, mastering the measurement methods and techniques of high-resistance resistors is of great significance for the design, testing and maintenance of electronic equipment. This article will focus on the measurement of high-resistance resistors and introduce in detail the relevant measurement principles, instrument selection, precautions and common misunderstandings to help readers fully understand the measurement technology of high-resistance resistors.

High-resistance resistors generally refer to resistors with a resistance above 1MΩ, which can even reach the GΩ level. This type of resistor is widely used in high-voltage circuits, electrostatic protection, sensor circuits and precision instruments. For example, the input impedance of charge amplifiers and oscilloscope probes require high-value resistors to ensure signal integrity and stability.

Due to the extremely high resistance, it is easily affected by environmental noise, leakage current and the internal resistance of the instrument during measurement, resulting in inaccurate measurement results. In addition, the temperature coefficient of high-resistance resistors is large, and temperature changes in the measurement environment will also have a significant impact on the results. Therefore, how to effectively isolate interference and ensure a stable measurement environment is the key to high resistance resistance measurement.

Commonly used instruments for measuring high-value resistors include megohmmeters, electrometers, precision bridges, and the high-resistance measurement mode in digital multimeters. The megohmmeter uses the principle of high-voltage power supply and current measurement and is suitable for measuring insulation resistance; the precision bridge achieves high-precision measurement through the balanced measurement method. When selecting an instrument, comprehensive considerations should be made based on the resistance range and accuracy requirements.

(1) Static measurement method: In the absence of external voltage, the resistance value is calculated by measuring the voltage and current at both ends of the resistor, which is suitable for low current environments.

(2) High-voltage measurement method: By applying a certain high-voltage voltage, the measurement current is enhanced and the measurement accuracy is improved, but attention must be paid to safety and the rated voltage of the resistor.

(3) Bridge method: Use Wheatstone bridge or special bridge to achieve balanced measurement, which has high accuracy and can effectively offset environmental interference.

In order to improve the accuracy of measurement, the measurement environment must be kept clean and dry to avoid the influence of humidity and dust on the resistance value. At the same time, when measuring, you should stay away from strong electromagnetic interference sources and use well-shielded measurement lines and fixtures to reduce leakage current and noise interference.

Regular calibration of measuring instruments is the basis for ensuring measurement accuracy. Use standard resistors for calibration and correct instrument deviations based on measurement results. In addition, attention should be paid to the contact resistance and temperature drift during the measurement process, and compensation technology should be used for error correction if necessary.

Misunderstandings include ignoring the effects of environmental humidity, using unsuitable measuring instruments, and ignoring leakage from wiring and fixtures. Measurements should be carried out in strict accordance with the operating procedures to avoid errors caused by human factors.

The measurement technology of high resistance resistors involves many aspects such as instrument selection, measurement methods, environmental control and error correction. By rationally selecting measuring instruments, adopting appropriate measurement methods, and strictly controlling the measurement environment, the accuracy and stability of measurement can be effectively improved. Mastering these key technologies will enable electronic engineers and testers to better complete the measurement tasks of high-resistance resistors and ensure the performance and safety of electronic equipment. It is hoped that the introduction of this article can provide valuable reference and guidance for practitioners in related fields.