1. Select by function
In addition to the five functions of measuring AC and DC voltage, AC and DC current, and resistance, the current clamp meter also has digital calculation, self-checking, reading hold, error reading, diode detection, word length selection, IEEE-488 Interface or RS-232 interface and other functions should be selected according to specific requirements.
2. Select by accuracy
The maximum allowable error of the clamp meter depends not only on its variable term error, but also on its fixed term error. When choosing, it also depends on the requirements of stability error and linear error, and whether the resolution meets the requirements. If the general digital multimeter requires grade 0.02 to 0.05, at least 4 and a half digits should be displayed; below grade 0.1, at least 3 and a half digits should be displayed.
Clamp meters have many ranges, but their basic range is the most accurate. Many clamp meters have an automatic range function, which makes the measurement convenient, safe and fast without manual adjustment of the range. There are also many digital multimeters with over-range capability. When the measured value exceeds the range but has not reached the maximum display, it is not necessary to change the range, thereby improving the accuracy and resolution.
Compared with the digital multimeter, the analog clamp meter has a much lower level of accuracy, the DC voltage accuracy level is basically 1.5 to 2.5, and the AC voltage accuracy level is 2.5 to 5.
3. Select according to the maximum range
Most clamp meters not only have a wide range distribution, but also have a high maximum range. Generally speaking, the DC voltage can reach 1000 V and the current can reach 20 A, and the AC voltage can reach 750 V or 1 000 V. The current is the same as is 20A. It should be noted that the measurement principle of the large current range is to convert the current value into a voltage value through a shunt, so it will have a certain impact on its accuracy. The resistance range is 20 MΩ to 200 MΩ, which can basically meet the needs of use. However, most analog multimeters have fewer ranges, and the maximum AC and DC voltage ranges are 500 V, and the AC and DC currents are mostly 0.5 A or 5 A, which may not meet the needs of some users.
