User`s guide

Measurement Tutorial 3
34450A User’s Guide 93
Capacitance measurements
The multimeter implements capacitance measurements by
applying a known current to the capacitor as shown below:
Figure 3-6 Applying current to the capacitor
Capacitance is calculated by measuring the change in voltage
(ΔV) that occurs over a “short aperture” time, (Δt). The
measurement cycle consists of two parts: a charge phase and
a discharge phase.
The change in voltage (DV) and “short aperture” time (Dt),
vary by range, in order to minimize noise and increase
reading accuracy. The following table lists the current source
and reading rate at full scale during the measurement.
Measurement Model
(during charge phase)
Measurement Model
(during discharge phase)
C
offset
V
charge
d
C
R'
R
P
C
C
offset
Range Current Source Reading Rate at Full Scale
1 nF 100 nA 1.0/second
10 nF 100 nA 0.5/second
100 nF
1
µA
1.5/second
1
µF
1
µA
0.25/second
10
µF 10 µA 0.25/second
100
µF100 µA 0.25/second