Six Precautions for Using a Multimeter
A multimeter is a multifunctional and multi range measuring instrument. Below are the considerations for selecting a multimeter.
1. Function: When using, it should be selected according to specific requirements.
2. Range and Range: A digital multimeter has many ranges, but its basic range accuracy is the highest. Many digital multimeters have an automatic range function, which eliminates the need to manually adjust the range, making measurement convenient, safe, and fast. Many digital multimeters also have the ability to overrange, so there is no need to change the range when the measured value exceeds the range but has not yet reached the maximum display, thereby improving accuracy and resolution.
3. Accuracy: The maximum allowable error of a digital multimeter depends not only on its variable term error, but also on its fixed term error. When choosing, it also depends on the requirements for stability error and linearity error, and whether the resolution meets the requirements. If a general digital multimeter requires levels 0.0005 to 0.002, it should have at least 61 digits displayed; 0.005-0.01 level, with at least 51 digits displayed; Level 0.02 to 0.05, with at least 41 digits displayed; Below level 0.1, there should be at least 31 digits displayed.
4. Input resistance and zero current: Both low input resistance and high zero current of a digital multimeter can cause measurement errors. The key lies in the allowable limit value of the measuring device, which depends on the internal resistance of the signal source. When the impedance of the signal source is high, instruments with high input impedance and low zero current should be selected to make their impact negligible.
5. Serial mode suppression ratio and common mode suppression ratio: When there are various interferences such as electric fields, magnetic fields, and various high-frequency noise, or when conducting long-distance measurements, it is easy to mix interference signals, resulting in inaccurate readings. Therefore, instruments with high serial and common mode suppression ratios should be selected according to the usage environment, especially when conducting high-precision measurements. A digital multimeter with protective terminal G should be selected to effectively suppress common mode interference.
6. Display form and power supply: The display form of a digital multimeter is not limited to numbers, but can also display charts, text, and symbols for on-site observation, operation, and management. According to the external dimensions of its display devices, it can be divided into four categories: small, medium, large, and ultra large.
