Guide for purchasing clamp type ammeters How to maintain ammeters well
A clamp type ammeter is a combination of a current transformer and an ammeter. The iron core of the current transformer can be opened when the wrench is tightened; The wire through which the measured current passes can pass through the open gap of the iron core without cutting it off. When the wrench is released, the iron core closes.
Working principle of clamp ammeter:
The tested circuit wire passing through the iron core becomes the primary coil of the current transformer, where the current is induced in the secondary coil through the current. Thus, the ammeter connected to the secondary coil has an indication - to measure the current of the tested circuit. The clamp meter can be changed to different ranges by shifting the gears of the switch. However, it is not allowed to operate with power when shifting gears. The accuracy of clamp shaped watches is generally not high, usually ranging from 2.5 to 5 levels. For ease of use, there are also conversion switches with different ranges in the meter for measuring different levels of current and voltage.
Guidelines for purchasing clamp ammeters:
(1) Firstly, it should be clear whether the measured current is AC or DC. The rectifier clamp type ammeter is only suitable for measuring power frequency currents with low waveform distortion and little frequency change, otherwise it will result in significant measurement errors. For electromagnetic clamp ammeters, the deflection property of the movable part of the measuring mechanism is independent of the polarity of the current. Therefore, it can be used to measure both AC current and DC current, but the accuracy is usually relatively low. The accuracy of clamp type ammeters mainly includes levels 2.5, 3, and 5, and should be selected based on measurement technical requirements and actual situations.
(2) For digital clamp ammeters, the reading of their measurement results is intuitive and convenient, and the measurement functions have also been expanded to measure parameters such as resistance, diode, voltage, active power, reactive power, power factor, frequency, etc. However, digital clamp ammeters are not perfect. When electromagnetic interference in measurement situations is severe, the displayed measurement results may experience discrete jumps, making it difficult to confirm the actual current value; If a pointer type clamp type ammeter is used, due to the damping effect of the magnetoelectric mechanical meter head itself, its response to strong electromagnetic field interference is relatively slow. At best, the meter needle produces a small amplitude of oscillation, and its reading range is relatively intuitive, making it relatively easy to read.
How to maintain an ammeter properly
Before use, the instrument needs to be powered on for 15 minutes.
2. Pay attention to preventing vibration and impact, and do not use in areas with excessive dust and harmful gases.
3. The input wire should not be too long. If the input end of the measured signal is too long, please try using twisted pair shielded wire.
If the signal is accompanied by high-frequency interference, a low-frequency filter should be tried online.
5. When stored unused for a long time, please power on every three months for no less than 4 hours.
6. Long term storage should avoid direct sunlight and should be stored at an ambient temperature of -25 ° C to 55 ° C
If there is no display on the instrument, the auxiliary power supply should be checked first to see if the voltage is within the range.
8. If the display is abnormal, check whether the input signal is normal and whether the signal terminals are tightened.
9. Unless the PT has sufficient power, the PT signal cannot be used as an auxiliary power source to ensure the normal operation of the instrument.
10. The current wiring terminal screws in the CT circuit must be tightened to ensure reliable contact between the incoming and outgoing lines to avoid faults.
If an instrument needs to be calibrated, the calibration instrument should be better than level 0.1 to ensure calibration accuracy.
