Metrohm 791 VA Detector - Manual (Page 41)

4.4 Instrument test with the dummy cell
791 VA Detector
35
4 Set all commutators 3 … 7 to "off" position
(non-depressed position).
5 Set selector 20 on the rear panel to +.
6 Set selector 21 on the rear panel to 0 … 10 mV.
0...10 mV
0...1 V
7 Bring recorder of voltmeter to 0 using potenti-
ometer 10 I
comp
rel.. The value shown on the
knob scale must not vary from 0 by more than
120 scale divisions.
Icomp
. I 0.01
8 Depress commutator 3 "meas": The recorder or
voltmeter should read –10 mV.
meas
9 Depress commutator 4 "damp" and wait until
recorder of voltmeter have attained a stable
position.
damp
10 Set commutator 3 "meas" to "off" position: The
time constant τ to be measured, i.e. the time
which has to elapse until 63.2 % of full-scale
deflection is reached, should have a value of
app. 3 s (consider τ of recorder or voltmeter).
meas
4.4.2 Check output voltage
1 Set digital switch 11 U
pol
to 0 mV.
0 0 0 +
2 Set adjusting knob 8 to 0.1 µ A.
4
5
1
10
50
1
5
0,1
0,5 100
10
0,5
0,1
3 Set commutators 4 … 7 to "off" position (non-
depressed position).