Clip on meter | Working | technical specifications

Clip on meter

The clip-on ammeter is designed to give a quick indication of current and direction flow, without breaking the circuit There are no connections to be made, it simply clips over the conductor. Thus clip-on ammeter avoids the necessity of breaking the circuit to measure the current. Clip-on ammeter operates on the principle of induction. i It consists of a current transformer with a single conductor asi shown in Fig. 4.12.1. The current flowing through this conductor is actually measured.

This meter measures the large ac current flowing through thei conductor with a dc ammeter. So a bridge rectifier is used asi shown in Fig. 4.12.1
This rectifier rectifies the ac induced current in the secondary of the current transtormer.
The universal shunt is an adjustable resistance which appears
in parallel with the DC meter. It is used for selection of range.i

Working:

When the core is clipped onto a cable, the cable under test acts as the single turn primary winding of a transformer and secondary is connected to D.C. ammeter.
Primary has a single turn (the conductor through which thei current to be measured is flowing), but secondary has many turns. So it acts as a step up transformer.
Due to ac current flowing through the conductor (primary), there is an induced ac current flowing in the secondary. 'Thei secondary current is about 10% of the pnimary current. The bridge rectifier converts this ac current into a direct i current (dc) and applies it to the dc ammeter.
The deflection of the dc ammeter is proportional to thei rectified secondary current. i
We can calibrate the meter scale to measure the current through the conductor directly.
As shown in Fig. 4.12.1, a trigger switch is used to split the core of the transformer and hence core can be clamped around a live conductor for the current measurement. With change in shunt resistance by changing the position of the current range selector switch, various ranges of D.C. i milli-ammeter can be obtained. i
Thus clip-on ammeter is used for measuring maximum current in a line, real and reactive powers and the power factor.

Technical specifications :

Standard range
Calibration accuracy : Movementi
Temperature range Cable size
30/0/30A, 70/075A± 10% of f.s.d. Moving magnet. -20℃℃ to +40℃℃。
For best results use with cable sizes Smm to TOmm diameter.
The clip on ammeter is used for high ac current measurement without breaking the circuit.