Technical data

36 Agilent U1251B/U1252B User’s and Service Guide
2 Making Measurements
Testin g Di ode s
To test the diodes, turn the circuit power off, and remove
the diodes from the circuit. Then proceed as follows:
1 Set the rotary switch to .
2 Connect the red and black test leads to the input
terminals and COM respectively.
3 Use the red probe lead on the positive terminal (anode)
and use the black probe lead on the negative terminal
(cathode).
4 Read the display.
5 Reverse the probes and measure the voltage across the
diodes again. 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).
NOTE
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.