Standard for measuring current with AC clamp meters
In circuits with high current, clamp type ammeters are generally used for measurement, which is relatively safe;
Firstly, set the multimeter to the current range, 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, attention should be paid to polarity. Whether measuring current or voltage, the meter should 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 the maximum value when unknown.
When measuring current, it is necessary to connect the ammeter 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 connected incorrectly, it is connected in parallel with the load, as the internal resistance of the ammeter is very small. Under the voltage of the load, a larger current will flow, causing damage to the ammeter.
When measuring voltage, it is necessary to connect the voltmeter in parallel with the load, as in the parallel circuit, the voltage in any branch is equal, which means that the voltage at both ends of the voltmeter is the actual voltage of the load. If the voltmeter is inserted into the load circuit, the actual voltage cannot be measured.
The structure of a clamp type ammeter is actually an AC current transformer. It is equivalent to a transformer with only one turn in the primary and many turns in the secondary, with the secondary load being the previous AC ammeter.
When a clamp type ammeter is clamped into a phase line, it is equivalent to having a winding. At this point, the working current induces a magnetic flux in the iron core circuit of the clamp ammeter, which passes through the secondary winding to induce a secondary voltage and form a current in the secondary load. The magnitude of this secondary current is directly proportional to the primary current, so that the value indicated by the meter can indirectly reflect the magnitude of the primary working circuit current. So it doesn't need to disconnect the circuit to measure current.
