Analysis of Error in Resistance Measurement by Ohmmeter

In the field of electronic measurement, ohmmeter is the measurementresistanceimportant tool for value. However, in the actual measurement process, there is often a certain error in the resistance measured by the ohmmeter. Understanding the sources of these errors and their influencing factors is of great significance to improving measurement accuracy and reliability. This article will conduct a systematic analysis around the resistance measurement error of the ohmmeter to help readers gain an in-depth understanding of the causes of errors and how to deal with them.

The ohmmeter provides current through the internal battery, flows through the resistance being measured, and displays the resistance value based on the current size and voltage change. The measurement method is essentially a calculation using Ohm's law (R=U/I). Since the measurement process involves the influence of current, voltage and internal circuits, errors are inevitable.

The ohmmeter relies on battery power, and the stability of the battery voltage directly affects the measurement accuracy. When the battery voltage drops, the measurement current decreases, causing the meter needle to deviate, which manifests as a larger or smaller measured resistance value. Therefore, keeping the battery voltage stable is the key to reducing errors.

The sensitivity and scale design of the ohmmeter determine the accuracy of the reading. Insufficient sensitivity of the meter head or unreasonable scale mark design will cause reading errors. In addition, mechanical wear or aging will also affect the pointer position of the meter head, causing reading deviations.

During measurement, poor contact between the test line and the resistance being measured will produce additional contact resistance, which will be superimposed on the resistance being measured, causing the measured value to be high. Especially in micro-resistance measurement, the impact of contact resistance is particularly significant, and good contact conditions must be ensured.

The resistance value itself changes with temperature, and different materials have different temperature coefficients of resistance. Fluctuations in ambient temperature will cause changes in the resistance value being measured, thus affecting the measurement results. Additionally, temperature drift in the ohmmeter's internal components can introduce errors.

The test wire itself has a certain resistance, especially when it is a long or thin wire, its resistance cannot be ignored. The resistance of the test line is connected in series with the resistance being measured, causing the reading to be too high. Using low-resistance test leads or performing line resistance compensation are effective ways to reduce errors.

Ohmmeters usually have multiple ranges, and improper selection will lead to a decrease in measurement accuracy. When the measuring range is too large, the resolution is reduced and the readings are inaccurate; when the measuring range is too small, the meter needle may exceed the measuring range and cannot read correctly. Reasonable selection of measuring range is the prerequisite to ensure accurate measurement.

Some special resistive components (such asthermistor、Varistor) has nonlinear resistance characteristics, and the resistance measured by the ohmmeter is different under different currents, resulting in unstable readings. For such components, special measurement methods or instruments should be used.

Ohmmeter resistance measurement errors come from various sources, involving internal battery, circuit design, test environment and characteristics of the component under test, etc. By properly maintaining the ohmmeter, selecting the appropriate range, ensuring good contact, and controlling the ambient temperature, measurement errors can be effectively reduced and measurement accuracy improved. Understanding and mastering these error analyzes will help engineering and technical personnel perform resistance measurements more accurately in actual work to ensure the performance and safety of electronic equipment.