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 functions such as digital calculation, self-test, reading hold, error readout, diode detection, and word length selection. should be selected according to specific requirements.
range and range
Clamp meters have many ranges, but the 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 clamp meters 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.
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 linearity error, and whether the resolution meets the requirements.
Input resistance and zero current
The input resistance of the clamp meter is too low and the zero current is too high, which 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.
Display form and power supply
The display form of the clamp meter is not limited to numbers, but also can display charts, texts and symbols for on-site observation, operation and management. According to the size of its display device, it can be divided into four categories: small, medium, large and super large. The power supply of the clamp meter is generally 220V, and some new clamp meters have a wide power supply range, which can be between 1100V and 240V. Some small clamp meters can be used with batteries.
Response time, measurement speed, frequency range
The shorter the response time, the better, but some meters have a longer response time, and it takes a while for the reading to stabilize. Measurement speed should be based on whether it is used in conjunction with system testing. For example, when combined, speed is important, and the faster the better. The frequency range is appropriately selected according to the needs.
AC voltage conversion form
AC voltage measurement is divided into average value conversion, peak value conversion and RMS conversion. When the waveform distortion is large, the average value conversion and peak value conversion are inaccurate, while the RMS conversion can not be affected by the waveform, so that the measurement results are more accurate.
Resistance wiring method
There are four-wire and two-wire wiring methods for resistance measurement. For small resistance and high-precision measurement, the resistance measurement wiring method with four-wire system should be selected.
