AC clamp ammeter measuring current standard
In the line with large current, it is generally safe to use clamp ammeter to measure;
First set the multimeter to the current gear, and then connect it in series in the circuit of the current to be measured. It should be noted that if it is a DC circuit, pay attention to the polarity. Whether measuring current or voltage, the ammeter must be adjusted to the corresponding gear, that is, the gear of the meter should be higher than the voltage or current value of the measured object. Adjust to maximum value when unknown.
When measuring current, the ammeter must be connected in series with the load, because the current in the series circuit is equal everywhere, so the current passing through the ammeter is the load current to be measured. If it is wrongly connected, it is connected in parallel with the load, because the internal resistance of the ammeter is very small, and under the voltage of the load, a large current will pass through it, which will damage the ammeter.
When measuring voltage, it is necessary to connect the voltmeter in parallel with the load, because in the parallel circuit, the voltage in any branch is equal, that is, the voltage at both ends of the voltmeter is the actual voltage of the load, if the meter is inserted into the load circuit, it cannot be measured actual voltage.
The structure of the clamp ammeter is actually an AC current transformer. It is equivalent to a transformer with only one primary turn and many secondary turns, and the secondary load is the previous AC ammeter.
When the clamp ammeter clamps a phase line, it is equivalent to having a primary winding. At this time, the working current induces a magnetic flux in the iron core circuit of the clamp ammeter, and the magnetic flux passes through the secondary winding to induce a secondary voltage and form a current in the secondary load. The size of this secondary current is directly proportional to the primary current, so the value indicated by the gauge head can indirectly reflect the size of the primary working circuit current. So it doesn't need to break the circuit to measure current.
