Metrohm 791 VA Detector - Manual (Page 44)

4 Maintenance – Malfunctions
791 VA Detector
38
4.4.4 Check of current and voltage overload
1 Set digital switch 11 U
pol
to +10 mV or
–10 mV.
0 0 1 +
2 Set adjusting knob 8 to 50 nA.
4
5
1
10
50
1
5
0,1
0,5 100
10
0,5
0,1
3 Set selector 20 on the rear panel to –.
4 Set selector 21 on the rear panel to 0 … 1 V.
0...10 mV
0...1 V
5 Set potentiometer 9 I
comp
abs. to 0.
0.02 nA
Icomp
6 Set commutators 3 … 7 to "off" position (non-
depressed position).
7 Bring recorder of voltmeter to 0 using potenti-
ometer 10 I
comp
rel..
Icomp
. I 0.01
8 Set commutator 6 " × 50" to "on" position
(depressed position).
x50
9 Turn potentiometer 9 I
comp
abs. clockwise until
overload display 2 lights up: The voltage at the
recorder output should be app. 10.5 … 12 V.
Without digital voltmeter, read the value on the
scale of potentiometer 9: The value should be
between 500 and 620 scale divisions.
0.02 nA
Icomp
10 Reset potentiometer 9 I
comp
abs. to 0: The
overload display 2 extinguishes.
0.02 nA
Icomp