A step-down transformer changes a voltage from one level to a lower level. The input voltage goes to a coil of wires called a primary, which induces a voltage into another coil of wires called a secondary. The amount of voltage induced into the secondary depends on the number of turns of wire in the coils of the primary compared to the secondary. A ratio of 10:1 turns will step normal household voltage from 120 down to 12 volts. You need to know how to use a voltmeter and work safely around electrical circuits to test a step-down transformer.
- Skill level:
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Things you need
- Specification sheet for your step-down transformer
- Multimeter with an AC voltmeter scale
Find out the specified output voltage of your step-down transformer from its specification sheet.
Apply power to your step-down transformer.
Set up your multimeter to read AC volts at a scale above the voltage you expect to read.
Touch the two leads of your voltmeter to the output terminals of your transformer. If the transformer is OK, the voltmeter should read the same voltage as in the step-down transformer's specifications.
Tips and warnings
- Don't confuse a step-down transformer with a charger. Although a charger may have a step-down transformer inside, the output will be DC and you will have to check it with the DC scale of your voltmeter.
- Never attempt to read the output of a power company transformer by climbing a telegraph pole or opening a power company transformer cabinet. If you have questions or problems with your power, call your power company.
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