Fluke 189 - Manual (Page 48)

Model 187 & 189
Users Manual
3-12
Measuring Capacitance
Caution
To avoid possible damage to the meter or to
the equipment under test, disconnect circuit
power and discharge all high-voltage
capacitors before measuring capacitance.
Use the dc voltage function to confirm that
the capacitor is discharged.
Capacitance is the ability of a component to store an
electrical charge. The unit of capacitance is the farad (F).
Most capacitors are in the nanofarad (nF) to microfarad
(
µ
F) range.
The meter measures capacitance by charging the
capacitor with a known current for a known period of time,
measuring the resulting voltage, then calculating the
capacitance. Capacitors larger than 100
µ
F take several
seconds to charge. The capacitor charge can be up to
3 V.
The meter’s capacitance ranges are 1 nF, 10 nF, 100 nF,
1
µ
F, 10
µ
F, 100
µ
F, 1 mF, 10 mF, and 50 mF.
To measure capacitance, set up the meter as shown in
Figure 3-8. The blue key toggles the selection between
capacitance and diode test.
While measuring capacitance, the following pushbutton
functions are not available:
•
Frequency (
N
)
•
FAST MN MX ( O M )
The following are some tips for measuring capacitance:
•
To speed up measurements of similar values, press
R to manually select the proper range.
•
To improve the measurement accuracy of small value
capacitors, press
D with the test leads open to
subtract the residual capacitance of the meter and
leads.