Important Elements of Clamp Ammeter Operation
1. Security requirements
1) In actual work, it is often necessary to measure the current value of low-voltage wires or equipment. In the measurement of the current of the low-voltage bus and its electrical components in the power distribution device, the distance between the lines of the general low-voltage bus is not large enough, and some clamp ammeters have a large size, and opening the jaws during measurement may cause phase-to-phase Short circuit or ground, if the surveyor's posture is unstable or his arm shakes, accidents are more likely to occur.
Therefore, it is necessary to use qualified insulating materials to isolate the busbar and electrical components from phase to phase before measurement according to the actual conditions on site, and care should be taken not to touch other live parts.
2) When measuring the current of bare conductors, if the distance between different phase conductors and between the conductors and the ground is small, if the jaw insulation is poor or the insulation sleeve is damaged, it is easy to cause phase-to-phase, phase-to-phase Short circuit accident between ground.
Therefore, it is generally stipulated that it is not allowed to use a clamp ammeter to measure the current of the bare wire. If it must be measured, safety preparations for the insulation and isolation of the bare wire should be made to prevent accidents from happening.
3) For the multi-purpose clamp ammeter, various functions cannot be used at the same time. For example, when measuring the current, the voltage cannot be measured at the same time. For safety reasons, the test line must be unplugged from the clamp ammeter.
4) At the measurement site, all kinds of equipment should be in order, and the distance between each part of the measurement personnel's body and the charged body must be kept large enough, at least not less than the safety distance (the safety distance of the low-voltage system is 0.1m-0.3m) . When reading, you will often lower your head or lean your waist involuntarily. At this time, special attention should be paid to the limbs, especially the safe distance between the head and the live part.
2. Accuracy requirements
1) When measuring current, the gear position of the clamp ammeter should be selected appropriately. It is best to make the needle fall on the scale above 1/3 of the scale, because the deflection angle of the needle is too small, and the scale value is not easy to distinguish, which affects the measurement accuracy. Accuracy.
2) The measured wire should be placed in the center of the jaw as much as possible. If the measured wire is too skewed, the magnetic induction intensity generated by the measured current in the jaw core will change significantly, which will directly affect the measurement. Accuracy, generally due to the improper position of the measured wire in the jaw, the measurement error can reach 2%-5%.
3) In order to make the reading accurate, the two sides of the jaws of the iron core should be tightly closed. If you hear electromagnetic noise from the jaws or feel a slight vibration in the hand holding the clamp ammeter, it means that the end faces of the jaws are not tightly bonded. At this time, you should re-open and close the jaws; if the noise still exists, check the clamps. Check whether there is any dirt or rust on the end surface of the jaws. If there is any, it should be cleaned until the jaws are well combined.
4) For the digital clamp ammeter, although the battery power has been checked before use, you should also pay attention to the battery power status during the measurement process. If the battery voltage is found to be insufficient (such as a low voltage prompt symbol), you must Continue the measurement after replacing the battery; if there is electromagnetic interference at the measurement site, it will inevitably interfere with the normal progress of the measurement, so try to eliminate the interference. Whether the measurement data can be read correctly is also directly related to the accuracy of the measurement.
5) For the meter head of the pointer clamp meter, firstly, check the selected gear, and secondly, check which scale is used. When observing the scale value pointed by the hands of the watch, the eyes should face the hands and the scale directly to avoid strabismus and reduce parallax. Although the display of the digital meter is relatively intuitive, the effective viewing angle of the LCD screen is very limited. It is easy to read the wrong number when the eyes are too skewed. You should also pay attention to the decimal point and its position, which must not be ignored. .
6) Abnormal or drastic changes in the temperature of the measurement site will affect the accuracy of the measurement. Because changes in temperature will increase the error of the meter, thereby reducing its accuracy. The main reason why the clamp ammeter is affected by temperature is that the temperature change changes the results of the material properties of the key structural parts of the meter.
For example, after the ambient temperature changes, the elasticity of the hairspring that produces the reaction torque of the meter often changes, so that the value of the meter changes accordingly, and the magnetism of the permanent magnetic field that forms the magnetic field changes, so that the magnitude of the acting torque of the meter changes.
In addition, due to changes in ambient temperature, the resistance of the circuit that constitutes the instrument, as well as the parameters of various electronic components and semiconductor devices will change, and the final result will affect the accuracy of the measurement.
7) During the measurement process, two or more wires cannot be clamped at the same time. When measuring a current less than 5A, in order to obtain a more accurate reading, if conditions permit, the wire can be wound several times and put into the jaw for measurement, but the actual current value should be the reading divided by the number of coils put into the jaw .
3. Storage requirements
1) After each measurement, the adjustment switch must be placed at the position of the maximum current range, in order to prevent the instrument from being damaged due to the unselected range in the next use.
2) It must be kept by a special person. When not in use, it should be stored in an indoor shelf or cabinet with a dry environment, suitable temperature, good ventilation, no strong vibration, no corrosive and harmful ingredients.
