How to Check for Low Voltage on a Transformer
A transformer can either step up or step down a voltage to a higher or lower level. If you suspect a low voltage output of your transformer, the problem could be either a low input or a defective transformer. So you need to check both input and output with a voltmeter. With hundreds of types of transformers used for a wide variety of applications, you need to know the correct input and output voltages of your transformer. You also need to know how to use a voltmeter safely, as you must work around energized and potentially dangerous equipment.
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Instructions
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A digital multimeter gives more accurate readings. Set your multimeter up to read AC volts at a range higher than the voltage you expect to read.
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Use caution working on energized transformers. Touch the leads to the primary connections of your transformer. The reading should be within the tolerances in the transformer's specifications for the expected output. With a low reading, you must have the problem corrected before going on, as the output will be low, even with a properly working transformer.
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Touch the leads of your voltmeter to the secondary of the transformer. Some transformers have more than one secondary or windings "tapped" for different outputs. Check every output because one output could be low when all the others are OK. Compare your readings with the specifications of the transformer.
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Tips & Warnings
Some digital multimeters have automatic ranging, so you don't need to select a range.
Always use extreme caution working around energized electrical equipment. Never work alone.
Use well-insulated test leads. Shorting an output could ruin your equipment.
If your meter does not have automatic ranging, be sure to set it to a proper scale. If not, you could damage your meter.
References
- Photo Credit analog multimeter full image by Paul Moore from Fotolia.com polimetro image by ANTEQUERANUS from Fotolia.com power supply image by pmphoto from Fotolia.com
