5
Application Examples
108
Keysight U1401B User’s and Service Guide
Diode Test
A good diode allows current to flow in one direction only.
To test a diode, turn the circuit power off, remove the diode from the circuit, and
proceed as follows:
1
Turn the rotary switch to the
/
position.
2
Connect the red and black probe leads to the positive and negative input
terminals respectively.
3
Probe the positive (anode) side of the diode with the red lead, and the negative
(cathode) side with the black lead.
4
Reverse the probe leads and measure the voltage across the diode again.
5
If the diode is:
– Good: In step 3, a forward voltage drop typically from 0.3 V to 0.8 V is
indicated (the instrument can display diode voltage drops up to
approximately 2.1 V) accompanied by a beep. In step 4,
OL
is indicated.
– Shorted: A voltage drop of nearly 0 V is indicated in both directions, and
the instrument will beep continuously.
– Open:
OL
is indicated in both directions.
NOTE
The cathode of a diode is the side indicated with band(s).