21
Selecting the TARE adjustment range
The TARE control can be bipolar if required. Set the jumpers on the
main board to give the appropriate adjustment range.
O
utput signal format selection
There are three sets of jumpers on the main board.
• Factory adjustments
Bridge excitation voltage equalisation adjustment
A factory adjustment on the power supply board ensures that the
negative and positive output voltages are equal. To adjust:
1
. Remove the top cover of the STG (screws marked A & B and the
equivalent on the right hand side).
2.
Connect up the instrument according to the table for calibration
(output multimeter not required).
3
. Adjust the voltage equalisation control (VR1) until the voltage across
test points TARE– and EX– is the same as the voltage between
TARE– and EX+.
C
MRR optimisation adjustment
The CMRR optimisation control minimises the sensitivity to 50 Hz
noise on the input signal. To adjust:
1. Remove the electronics from the housing.
2. S
hort the input terminals (7 & 8) together.
3. Apply a 10 V p/p 50 Hz AC signal between TARE – and the input
terminals (7 & 8).
4. Connect an oscilloscope across TARE – and TARE+.
5.
Adjust the CMRR control until the 50 Hz signal shown on the
oscilloscope is minimised.
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