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There's nothing like being caught between a rock and a hard place. This cannot be more aptly demonstrated by the need to accurately record the normal operating current of a load but also capture and record the level of a current transient. If a clamp sensitive enough to record the operating current is used, the risk is run of not knowing the true extent of any transient as the clamp or input may limit. If adjusted/selected to capture the event, the clamp and input may be operating within a range where resolution of the normal running current now becomes an issue. A real case of wanting one's cake and eating it too! The answer is actually quite simple. Many times there is a channel on the recorder that isn't being used, such as ground current etc. All that's required is to wire up all the important channels as usual, with all the correct size clamps for normal operating, and then wire in a suitable clamp for capturing the transient current on the unused channel. If the situation is a single phase supply then simply use a multi-phase recorder (it may be necessary to wire up the voltage input for the 'transient' channel too - investigate what is required). If a current transient occurs then the level is easily read from the high current channel, all this without losing the accuracy of normal running currents. Testing Power Factor Correction Capacitors >>
© 14.07.02 |
MEASUREMENT TECHNIQUES: