Measuring Principle of AC Clamp Meter
The working principle of the clamp ammeter is: based on the working principle of the current transformer, when the wrench of the clamp ammeter is held tightly, the iron core of the current transformer can be opened, and the wire of the measured current enters the inside of the jaw as a current mutual inductance primary winding of the device. When the core of the wrench is loosened and closed, an induced current is generated on its secondary winding according to the principle of the transformer, and the pointer of the ammeter deflects, thereby indicating the value of the measured current.
It is worth noting that: because the principle is to use the principle of the transformer, whether the iron core is tightly closed and whether there is a large amount of residual magnetism has a great influence on the measurement results. When measuring a small current, the measurement error will increase. At this time, the measured wire can be wound several times on the iron core to change the current ratio of the transformer to increase the current range. At this point, the measured current Ix should be:
In the formula, Ia is the reading on the ammeter; N is the number of winding turns.
The clamp meter is essentially composed of a current transformer, a clamp wrench and a rectifier magnetoelectric system with a reaction force. So the clamp meter is actually a combination of current mutual inductance and ammeter. Its closed iron core is opened, and the measured current-carrying wire is clamped into the iron core mouth. This wire is equivalent to the primary winding of a current transformer with 1 turn. The iron core is wound with a secondary winding and connected to the measuring instrument, which can directly read the value of the measured current. It is very convenient to use the clamp meter without disconnecting the circuit when measuring the current.
