Testing Diodes - Fluke 187 User Manual

189 LOGGING MULTIMETER
AutoHOLD FAST MN MX LOGGING YES
HOLD HOLD MIN MAX MIN MAX REL REL
NO
CANCEL SAVE
Hz Hz % % ms ms RANGE RANGE
SETUP
nS nS
F F
mV mV
C C
ac+dc ac+dc
A A
V V mA mA
ac+dc ac+dc
A A
mV mV
dB dB
A A
V V
dB dB mA mA
ac+dc ac+dc
A A
OFF OFF
ac+dc ac+dc
VIEW
CLEAR MEM
TEMPERATURE TEMPERATURE
mA mA
A A COM COM V V
A A
10A MAX
CAT
400mA
FUSED
FUSED 1000V
Figure 3-8. Capacitance Measurement

Testing Diodes

To avoid possible damage to the meter or to
the equipment under test, disconnect circuit
power and discharge all high-voltage
capacitors before testing diodes.
Use the diode test to check diodes, transistors, silicon
controlled rectifiers (SCRs), and other semiconductor
devices. The test sends a current through a
semiconductor junction, then measures the junction's
voltage drop. A typical junction drops 0.5 V to 0.8 V. In
diode test, the beeper is active. It beeps briefly for a
normal junction and is on continuously if a short is
detected.
To test a diode out of a circuit, set up the meter as shown
in Figure 3-9.
+
In a circuit, a similar diode should still indicate a forward-
+
+
+
+
bias reading of 0.5 V to 0.8 V; however, the reverse-bias
+
+
+
reading can vary depending on the resistance of other
pathways between the probe tips.
+
The blue key toggles between diode test and capacitance.
Since diode test uses a fixed range,
ach005f.eps
used.
Making Measurements
Testing Diodes
Caution
cannot be
3
3-13