Metrohm 791 VA Detector - Manual (Page 46)

4 Maintenance – Malfunctions
791 VA Detector
40
4.4.6 Check of noise from current amplifier
1 Connect dummy cell.
2 Set digital switch 11 U
pol
to 0 V.
0 0 0 +
3 Set adjusting knob 8 to 1 nA.
4
5
1
10
50
1
5
0,1
0,5 100
10
0,5
0,1
4 Set commutator 3 "meas" to "on" position
(depressed position).
meas
5 Set commutators 4 … 7 to "odd" position
(non-depressed position).
6 Set selector 21 on the rear panel to 0 … 1 V.
0...10 mV
0...1 V
7 Allow the recording instrument to record for a
longer period of time (first adjust chart recorder
to middle of the scale). Typical deflections
caused by noise are about 10 mVpp or less (the
656 housing must be earthed).