Why does an electric tester not work on DC current?
An electric tester is a device that detects the presence of voltage in a wire or an outlet.
It works by sensing a small amount of current that is capacitively coupled from the live circuit to the tester and back to ground.
The tester has a neon lamp that glows when it receives enough voltage, usually around 80 volts¹.An electric tester does not work on DC current because capacitors and transformers, which are used to couple the current, do not work with DC.
DC current has a constant polarity and does not change direction like AC current. Therefore, the tester cannot detect any voltage difference between the live wire and the ground².
If you want to test a DC circuit, you will need a different device, such as a multimeter, that can measure the actual voltage level on the wire. A multimeter can also measure other electrical properties, such as resistance and current³.
However, you should be careful when using a multimeter on a live circuit, as it may cause a short circuit or damage the device if you use the wrong settings or probes.
Always read and follow the instructions and warnings that come with your multimeter before using it.