SRS Labs SR715 - C+D Accuracy

ACCURACY
3-6
C + D ACCURACY
Accuracy of C = ± [A x K
i
x K
v
+ (K
h
+ K
l
) x 100] %
A = Basic Capacitance Accuracy
Factor from graph.
For D > 0.1, multiply the basic
accuracy factor by (1 + D).
If the unit is in the constant voltage
(CV) mode or under internal or
external bias, double the basic
accuracy factor.
K
i
= Integration Time Factor (see K
i
Table below)
K
v
= Voltage Error Factor (see K
v
table
below).
K
h
, K
l
= Extreme Range Error Term (see
K
h
, K
l
table below).
Accuracy of D = ± [Ac / 100]
A
c
= the accuracy of the capacitance
measurement (above)
Note that the accuracy of D is specified as a
magnitude, NOT as a percent.
K
i
Table
Meas Rate Frequency
Z
m
K
i
slow, med all 1
fast 100 Hz-1 kHz 6.25 Ω<Z
m
<400 kΩ 3
fast all other 2
Z
m
= 1/2πfC = impedance of device
K
v
Table
V
out
(V rms) K
v
1.0 - 0.55 1 / V
out
0.5 - 0.3 0.5 / V
out
0.25 - 0.15 0.25 / V
out
0.10 0.11/V
out
Note that K
v
equals one for the primary drive
voltages (1.0, 0.5 and 0.25 Vrms).
K
h
& K
l
Table
Frequency K
l
K
h
100,120 Hz (2 pF / C
m
)(C
m
/ 1600 mF)
1 kHz (0.1 pF / C
m
)(C
m
/ 160 mF)
10 kHz (0.01 pF / C
m
)(C
m
/ 16 mF)
100 kHz (0.02 pF / C
m
)(C
m
/ 200 µF)
C
m
= the capacitance of the device being
measured.
Note that K
l
is negligible for capacitances less than
1590/f µF and K
h
is negligible for capacitances
above 159/f µF, where f is the output frequency.