Multimeter Question

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Kurt Wylde
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Multimeter Question

Post by Kurt Wylde »

Hello
It's been 25 years since I held a soldering iron; I have some questions regarding power supply construction and using the multimeter.

I assembled the power supply shown in the Content portion of the website, using a 12 volt transformer. When I put the meter on the transformer leads, the meter reads about 14.9 volts; however, when I attach the transformer to the power supply circuit the meter reads a single "1" on the far left of the lcd display. If I check the input and ground of the voltage regulator on the circuit, it likewise displays "1". If I check the output and ground of the voltage regulator, it reads a steady 4.96 volts. The power indicator led glows bright; and if I check the terminals that will supply the second circuit board, it reads a steady 4.96.

I am puzzled why the meter reads "1" when the transformer is attached to the circuit board. Any ideas? I assume that since I am getting 4.96 to supply the second board I'll be OK.

Thanks.
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craig_newbold
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Re: Multimeter Question

Post by craig_newbold »

The "1" you are seeing on the multimeter is there to let you know that the value (voltage in this case) that you are trying to measure is larger than the scale you are currently set to.

Your meter probably has various ranges that it allows for measuring DC voltage, resistance etc. If you switch the meter to a range that is higher you should be able to read the voltage on the primary side ok.

I haven't looked at the circuit you're working on, but if your power supply is converting AC input to a DC output, then some of your measurements will require the meter to be set on AC setting.

Regards,
- Craig
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