Diode Testing; Approximate Charge Rate For Capacitors - Fluke 87 TRUE RMS MULTIMETER User Manual

environments, use short test leads or a test fixture (1 nF =
1000 pF).
The measurement accuracy of capacitors less than 5 nF
can be improved by first using the Relative mode to zero
the display and automatically subtract the residual meter
and test lead capacitance. Since the Relative mode also
selects manual ranging, zero the residual capacitance
only when measuring small value capacitors.
Residual voltage charges on the capacitor, or capacitors
with poor insulation resistance or poor dielectric
absorption may cause measurement errors.
To check capacitors larger than 5 F, select
rotary switch (or press the BLUE button if you are in the
capacitance mode). Select an appropriate range from
Table 5. Discharge the capacitor, connect the capacitor to
the meter, and time the number of seconds it takes for the
charge to go from zero to full scale. At full scale, all of the
analog display segments are on. To estimate the value of
the capacitor, multiply the number of seconds times the
charge rate ( F/sec) in Table 5. For example, a 10 F
capacitor takes about 34 seconds to charge in the 4 M
range or 3.4 seconds in the 400 k
your estimate, reverse the test leads; when the capacitor
discharges to zero (the analog display polarity switches
from - to +), start timing the recharge to full scale.
with the
range. To reconfirm

Diode Testing

To perform a diode or transistor junction test: plug the test
leads into the VJL and COM inputs, turn the rotary
switch to L and connect the test leads across the
diode(s).
In diode test, voltage is developed across the
component(s) by a test current (approximately 0.6 mA with
the test leads shorted) from the meter. Voltage is read on
a single 0 to +3.000V range that can measure up to five
silicon diode or transistor junctions in series. For a silicon
diode, the typical forward voltage should be about 0.6V.
Voltages greater than 3.00V or open test leads produce
an overload (OL) reading. If the digital reading is the same
in both directions, the diode junction is probably shorted. If
the display reads OL in both directions, the diode junction
is probably open. To protect sensitive devices, the open
test lead voltage from the meter will not exceed 3.9V.
Negative inputs (from an external power source, for
example) are not suppressed.
Table 5. Approximate Charge Rate for Capacitors
Range 400 4 k
F/sec 2600 275
Applications
40 k 400 k 4 M
29 2.9 0.29
23