Making Measurements 2
Keysight U1251B and U1252B User’s and Service Guide 65
Testing Diodes
To test a diode, turn the power off to the circuit and remove the diode from the
circuit. Set up the multimeter as shown in Figure 2-10, then use the red probe
lead on the positive terminal (anode) and use the black probe lead on the negative
terminal (cathode) and read the display.
Next, reverse the probes and measure the voltage across the diodes again as shown
in Figure 2-11 on page 67. The diode’s test result is based on the following:
– The diode is considered good if the meter displays “OL” in reverse bias mode.
– The diode is considered shorted if the meter displays approximately 0 V in both
forward and reverse bias modes, and the meter beeps continuously.
– The diode is considered open if the meter displays “OL” in both forward and
reverse bias modes.
CAUTION
Disconnect the circuit power and discharge all the high-voltage capacitors
before testing the diodes to prevent any possible damage to the meter.
NOTE
– The cathode is the side with band(s).
– The meter can display the diode’s forward bias of up to approximately 2.1 V.
A typical diode’s forward bias is between the range of 0.3 V to 0.8 V.
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