Key points for measuring current with clamp meter
1) When measuring current, the selection of the gear level of the clamp ammeter should be appropriate. It is best to place the pointer on more than one-third of the scale because the deflection angle of the pointer is too small, making it difficult to distinguish the scale value and affecting the accuracy of the measurement.
2) The measured wire should be placed in the center position of the clamp as much as possible. If the measured wire is too skewed, the magnetic induction intensity generated by the measured current in the clamp iron core will undergo significant changes, directly affecting the accuracy of the measurement. Generally, measurement errors caused by improper positioning of the measured wire in the clamp can reach 2% -5%.
3) To ensure accurate readings, the two sides of the iron core clamp should be tightly closed. If you hear electromagnetic noise from the jaws or feel a slight vibration in the hand holding the clamp shaped ammeter, it indicates that the end face of the jaws is not tightly connected. At this time, the jaws should be opened and closed again; If the noise still exists, check whether there is dirt or rust on the end face of the jaws. If there is, clean it thoroughly until the jaws are well connected.
4) For digital clamp current meters, although the battery level has been checked before use, the battery level should also be monitored at all times during the measurement process. If the battery voltage is found to be insufficient (such as a low voltage prompt symbol), the measurement must be continued after replacing the battery; If there is electromagnetic interference on the measurement site, it will inevitably interfere with the normal progress of the measurement, so efforts should be made to eliminate the interference. The ability to correctly read measurement data is also directly related to the accuracy of the measurement.
5) For the header of a pointer type caliper, the first step is to identify the selected gear, and then identify which scale is being used. When observing the scale value pointed by the pointer, the eyes should be directly facing the pointer and scale to avoid strabismus and reduce parallax. Although the display of digital meter heads is relatively intuitive, the effective viewing angle of LCD screens is very limited. When the eyes are too skewed, it is easy to read the wrong numbers. Attention should also be paid to the decimal point and its position, which must not be ignored.
6) Abnormal or drastic temperature changes in the measurement location will affect the accuracy of the measurement. Because temperature changes can increase the error of the meter, thereby reducing its accuracy. The main reason why clamp ammeters are affected by temperature is that temperature changes alter the material properties of key structural components that make up the instrument.
When the ambient temperature changes, the elasticity of the balance spring, which often generates a reaction torque on the instrument, changes, resulting in a change in the instrument value. It can also cause a change in the magnetic properties of the permanent magnetic field that forms the magnetic field, resulting in a change in the magnitude of the instrument's applied torque.
In addition, due to changes in environmental temperature, the resistance of the circuits that make up the instrument, as well as the parameters of various electronic and semiconductor components, will all undergo changes, which will ultimately affect the accuracy of the measurement.
7) During the measurement process, two or more wires cannot be clamped simultaneously. When measuring currents below 5A, in order to obtain more accurate readings, if conditions permit, the wire can be wound a few more times and placed in the clamp for measurement. However, the actual current value should be the reading divided by the number of wire turns placed in the clamp.
