Test a diode with Digital multimeter DT-830B
The digital multimeter model DT-830B has a diode check range , It is a cheap multimeter so some testing display may different from an advance and higher price multimeter. Its diode check range will supply 2.8V and 1mA test current so you can use it to check LED and Zener diode too , as it supply very small test current to save battery life time so LED does not light , however , it still indicate good or bad condition by display voltage drop.
Step to test a diode with cheap multimeter.
1. Insert the red test lead to VΩmA terminal and the black test lead to COM terminal.
2. Turn the range switch to Diode check and it will display number 1 as above photo.
3. Forward bias to diode by connecting lead test with diode as below. Note the testing is done when diode is not on circuit and there is no voltage present on diode. Always remove power source from diode before testing.
4. Reverse bias to diode connect test lead with diode as photo below. The good diode will display number " 1 ". , it mean ∞ Ohm ( not connected or not shorted )
5. Bad diode (shorted ) always display 000 for forward biasing and reverse biasing.
6. Bad diode ( open ) always display number "1" for forward biasing and reverse biasing. This Time is mean ∞ Ohm as diode open so there is not forward voltage drop display and no current flow when forwarding biasing.
Read more of testing .
