Solutions to common problems with ammeters
A clamp type ammeter is a portable instrument that can measure current without connecting to a circuit. It is very convenient to use when it is inconvenient to disconnect wires or cannot cut off the circuit and current measurement is necessary. Its drawback is its low accuracy.
The clamp shaped ammeter consists of a clamp shaped movable iron core and an ammeter. The movable iron core is wrapped with insulation on the outside, connected to a wrench on one side, and equipped with an elastic spring. When measuring, use a finger wrench to open the iron core and wrap the current carrying wire inside the iron core window to measure the current in the wire.
To ensure accurate readings, the two clamp surfaces should be kept clean frequently to ensure good joint. When measuring, the current carrying wire should be clamped in the center of the clamp, and the measuring range should be reduced from the maximum gear to the appropriate limit.
Clamp type ammeters are divided into two types: clamp type AC ammeters and clamp type AC/DC ammeters. The two types of watches have the same appearance, but their principles and structures are different.
When using a clamp ammeter for testing, the following techniques can be applied:
1. Small current measurement: When measuring AC current below 5A, the wire can be wound several times and placed in the clamp for measurement. At this time, the actual current value is the indicated value divided by the number of turns made.
2. Measure the zero sequence current, determine whether the three-phase load is balanced and whether there is a phase break: Place the three-phase wires (or cables) into the pliers at the same time. If the reading of the meter needle is large, it indicates that the load is unbalanced or there is a phase break phenomenon.
3. If there is vibration or collision sound when inserting the wire into the pliers, the instrument wrench should be repeatedly turned or reopened until the noise is eliminated before reading.
After measuring a large current, if measuring a small current immediately, the jaws should be opened and closed several times to eliminate residual magnetism in the iron core.
Sometimes, there may be frequent shaking of the current test meter needle. In this case, the brake can be used to lock the pointer first, and then the reading can be stable and convenient.
6. When measuring, try to stay away from other current carrying wires to reduce measurement errors.
