16.1.2. Check of chains energized


Energized we check chains the voltmeter and the ampermeter.
The voltmeter is connected parallel to the checked device or the site of a chain. Limit of measurements of 0-15 or 0–25 V of a direct current. The negative wire (probe) is connected to "weight", positive – to consumers or sources of current. It is possible to determine malfunction of the feeding chain (break, oxidation of contacts, etc.), and also short circuit in the consumer by power failure.
For check of chains energized it is possible to use the control lamp with power no more than 3-4 W calculated on voltage of 12 V (for example, AMH12-3 lamp used in a combination of devices).
The ampermeter has to have the top limit of measurements 10 A and more direct current, and also protection against an overload. The ampermeter is connected consistently to the checked device. "Plus" of the device is connected to a current source, and "minus" to the consumer. We measure the consumed current and we compare it with nominal, specified in a technical characteristic of the checked device. As the actual tension in onboard network differs from nominal (in help data the rated current corresponds to rated voltage, i.e. 12 V), the received value can slightly differ from specified. If current is less demanded, then the electric chain is faulty and if more – there was a short circuit in the consumer.