Key points to remember when using a clamp ammeter
Security requirements
1) In actual work, it is often necessary to measure the current value of low-voltage wires or equipment. When measuring the current of low-voltage busbars and their electrical components in power distribution devices, generally the distance between the lines of the low-voltage busbars is not large enough. Some clamp-type ammeters are large in size. Opening the jaws during measurement may cause phase interference. Short circuit or grounding, if the measuring personnel's posture is unstable or their arms shake, accidents are more likely to occur.
Therefore, according to the actual conditions on site, qualified insulation materials must be used to isolate the busbars and electrical components from each other before measurement. At the same time, 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 the conductor 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 usually not allowed to use a clamp ammeter to measure the current of a bare conductor. If measurement is necessary, safety preparations should be made for the insulation and isolation of the bare conductor to prevent accidents.
3) For multi-purpose clamp ammeters, various functions must not be used at the same time. For example, when measuring current, voltage cannot be measured at the same time. For safety reasons, the test wire must be unplugged from the clamp ammeter.
4) At the measurement site, all equipment should be in order, and a sufficient distance must be maintained between various parts of the body of the measuring personnel and the live objects, at least not less than a safe distance (the safe distance for low-voltage systems is 0.1m-0.3m) . When taking readings, people often lower their heads or probe their waists involuntarily. At this time, special attention should be paid to the safety distance between the limbs, especially the head and the live parts.
Accuracy requirements
1) When measuring current, the level of the clamp ammeter should be appropriately selected. It is best to make the meter needle fall on more than 1/3 of the scale. Because the deflection angle of the meter needle is too small, the scale value is difficult to distinguish, which affects the measurement accuracy. Accuracy.
2) The wire to be measured should be placed in the center of the jaw as much as possible. If the wire to be measured is too skewed, the magnetic induction intensity generated by the measured current in the core of the jaw will change significantly, which will directly affect the measurement results. Accuracy, generally the measurement error caused by the improper position of the measured wire in the jaw can reach 2%-5%.
3) In order to obtain accurate readings, both sides of the iron core jaws should be tightly closed. If you hear electromagnetic noise emitted by 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 connected. At this time, the jaws should be opened and closed again; if the noise still exists, the clamps should be checked. Check whether there is dirt or rust on the mouth end surface. If so, clean it until the jaws are well combined.
4) For digital clamp ammeters, although the battery power has been checked before use, you should also pay attention to the battery power condition at any time during the measurement process. If the battery voltage is found to be insufficient (such as a low voltage prompt symbol appears), 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 measurement, so you should 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 type clamp meter, you should first identify the selected gear, and secondly identify which scale is used. When observing the scale value pointed by the watch hand, your eyes should face the watch hand and the scale to avoid squinting 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 misread the numbers when the eyes are too slanted. You should also pay attention to the decimal point and its location. This must not be ignored. .
6) Abnormal or drastic changes in temperature at 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 temperature changes change the material properties of the key structural components of the instrument.
For example, changes in ambient temperature often cause the elasticity of the hairspring that generates reaction torque in the instrument to change, causing the instrument value to change accordingly. It can also change the magnetism of the permanent magnetic field that forms the magnetic field, causing the magnitude of the instrument's acting torque to change.
In addition, due to changes in ambient temperature, the resistance of the circuits that make up the instrument, as well as the parameters of various electronic components and semiconductor devices will change, and the final results 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, you can wind the wire a few more times and put it into the jaws for measurement. However, the actual current value should be the reading divided by the number of wire turns placed in the jaws. .
Storage and placement requirements
1) After each measurement, be sure to place the adjustment switch in the position of the maximum current range to prevent damage to the instrument due to unselected range the next time it is used.
2) There must be a dedicated person to keep it. 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 components, and be properly kept.
