Most Important Test Tool
♦ If the security installer was allowed only one test tool they could fit into their pocket it would be a voltmeter.
There’s no question that voltage is the simplest and most practical of all electrical measurements. Not only is it easy to find whether voltage is there or not, it’s also an easy task to measure just how much voltage there is in a circuit and assess it against specifications.
The importance of correct voltage is that without voltage there’s no electical function. Without voltage, electrons will simply waggle about in space – they will not flow through a circuit and energise it.
Further, if there is too little voltage, current will drop and there may be insufficient current to drive the circuit. At the same time, if there is too much voltage, current will increase, and this increase may blow a circuit’s protective fuse.
To test voltage you connect the voltmeter across the load – negative probe on the negative side, positive probe on the positive side. This test measures the voltage potential of the circuit. Lock your meter scale to a range that’s greater than the known operating voltage of the circuit you’re testing before connecting the probes.
A voltmeter, combined with an understanding of the voltage of the power supply and the voltage required for proper operation of a circuit, may be all an experienced technician requires to establish the presence of a fault, assess the nature of a fault, and narrow down its source.
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