6 things to note when using a multimeter
A multimeter is a multi-functional, multi-range measuring instrument. Let’s talk about the issues you should consider when choosing a multimeter.
1. Function: Select according to specific requirements when using.
2. Range and range: Digital multimeters have many ranges, but their basic range has the highest accuracy. Many digital multimeters have an automatic range function, eliminating the need to manually adjust the range, making measurements convenient, safe and fast. There are also many digital multimeters with over-range capabilities. When the measured value exceeds the range but has not yet reached the maximum display, there is no need to change the range, thereby improving accuracy and resolution.
3. Accuracy: The maximum error allowed by a digital multimeter depends not only on its variable term error, but also on its fixed term error. When choosing, you also need to look at the requirements for stability error and linear error, and whether the resolution meets the requirements. For general digital multimeters, if the requirements are 0.0005 to 0.002, at least 61 digits should be displayed; 0.005 to 0.01, at least 51 digits should be displayed; 0.02 to 0.05, at least 41 digits should be displayed; 0.1 Below, at least 31 digits should be displayed.
4. Input resistance and zero current: Too low input resistance and too high zero current of the digital multimeter will cause measurement errors. The key depends on the limit value allowed by the measuring device, that is, the internal resistance of the signal source. When the signal source impedance is high, an instrument with high input impedance and low zero current should be selected so that its influence can be ignored.
5. Series mode rejection ratio and common mode rejection ratio: When there are various interferences such as electric fields, magnetic fields and various high-frequency noises or when long-distance measurements are made, interference signals are easily mixed in, causing inaccurate readings. Therefore, the values should be determined according to the use environment. Choose an instrument with a high string and common-mode rejection ratio. Especially when making high-precision measurements, you should choose a digital multimeter with protective terminal G, which can suppress common-mode interference well.
6. Display form and power supply: The display form of the digital multimeter is not limited to numbers, but can also display charts, text and symbols to facilitate on-site observation, operation and management. According to the external dimensions of its display device, it can be divided into four categories: small, medium, large and ultra-large.
