A decent mid-range multimeter will likely cost between $50-100 USD. Opt for a digital multimeter over an analog model, which will be harder to read and less reliable.
The diode symbol visually represents both its terminals, the cathode and the anode.
Make sure that the cathode and anode are not touching each other during this test, which may prevent the current from passing through the LED light and hinder your results. The black and red probes should also not be touching each other during the test. Making the connections should cause the LED to light up.
If your supply does not provide any output voltage, then the transformer needs to be replaced. If you have voltage on the output then LED lights are not working and need to be replaced.
Use either CR2032 or CR2025 coin cell batteries.
Coin cell battery holders are usually used to add battery power to small projects like LED jewelry or clothing.
Some battery holders with leads will come with a small connector on the end, holding the tips of the two leads. If your battery holder has a lead connector, test your LED by inserting the anode and cathode into the small openings that line up with the red and black leads.
If your LED doesn’t light up, try testing other LED lights right after it. If they light up, you can be sure that the first LED doesn’t work.
