Electronic – Power Supply Output Terminals not isolated

power supplyresistance

I have an 20v power adaptor. But I noticed that the output +ve and -ve terminals are not isolated. I mean if I measure the resistance between +ve and -ve terminals, it tells 10k ohms and keeps on rising. If I could find out anything on google it was some comparison between isolated and non-isolated converters. But I could not relate the info in my scenario. Any help would be great.

Edit: If I measure by keeping multimeter on 200k limit, it starts at 10k but if I switch it to 2000k limit, it starts from 100k.

Best Answer

The rising resistance is because the voltage at the meter is increasing as the supply output capacitor is charging from the meter. Behind the capacitor will be some sort of regulator which will be un-powered and therefore be high impedance.

A meter on ohms range applies a small fixed current to the load and then measures the output voltage. This gives resistance. If you connect your meter to a discharged capacitor it starts at a low reading because the capacitor voltage is low and then increases as the capacitor charges.

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