2 Operations and Features
28 U3402A User’s and Service Guide
To test a diode, switch the circuit power off, and remove the diode from the
circuit. Then proceed as follows:
1 Press . The default function is diode measurement.
2 Connect the red and black test leads to the input terminal as shown in
Figure 2- 8.
3 Connect the red test lead to the positive terminal (anode) of the diode and
the black test lead to the negative terminal (cathode). Refer to Figure 2- 8.
4 Read the display.
5 Reverse the probes and measure the voltage across the diode again (refer to
Figure 2- 9). Assess the diode according to the following guidelines:
• A diode is considered good if the multimeter displays OL in reverse bias
mode.
• A diode is considered shorted if the multimeter displays approximately
0 V in both forward and reverse bias modes, and the multimeter beeps
continuously.
• A diode is considered open if the multimeter displays OL in both forward
and reverse bias modes.
Disconnect circuit power and discharge all high-voltage capacitors before testing
diodes to avoid damaging the multimeter.
• Measurement method:
0.83 mA±0.2% constant current source, open-circuit voltage
limited to <5 V
• Response time:
70 samples per seconds with audible tone
• Gate time:
0.1 s or 1 period of the input signal, whichever is longer
• Input protection:
500 V RMS on all ranges
The cathode of a diode is indicated with a band.
U3402-90001.book Page 28 Friday, July 24, 2009 4:04 PM
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