Metrohm 791 VA Detector - Manual (Page 29)

3.3 Operating element functions
791 VA Detector
23
3.3 Operating element functions
Mains switch
~
The 791 VA Detector is switched on and off using mains switch
25 on the rear of the instrument (see Fig. 2):
I Instrument switched on
0 Instrument switched off
After the instrument has been switched on, the mains pilot lamp 1
lights up to show that the instrument is ready for use.
Relative compensation current
Icomp
. I 0.01
The relative compensation current I
comp
rel. is set using the
potentiometer 10 (see Fig. 1). The value set is related to the
setting of the adjusting knob 8 (current I).
Setting range –500 (red) … +500 (white) × 0.01 x I
Resolution 0.01 x I per scale division
Absolute compensation current
0.02 nA
Icomp
The absolute compensation current I
comp
abs. is set using the
potentiometer 9 (see Fig. 1). The value set is not related to the
setting of the adjusting knob 8 (current I).
Setting range
direct 0 … 1000 × 0.02 nA = 20 nA
with commutator 5 5 × 20 nA = 100 nA
with commutator 6 50 × 20 nA = 1000 nA
Resolution
direct 0.02 nA per scale division
with commutator 5 0.10 nA per scale division
with commutator 6 1.00 nA per scale division
The polarity of the absolute compensation current is set sepa-
rately with commutator 7.
Changeover Stand-by/Measure
meas For this changeover commutator 3 (see Fig. 1) is used.
Button depressed
Measuring position, i.e. measuring cell connected.
Button not depressed
Stand-by position, i.e. measuring cell disconnected.