10-4
10.2.5 POT Input range calibration
Connect the two decade resistor box at the input terminals of the unit and the multimeter at the output terminals
(current or voltage mode dependent to the output type) as shown in figure. Allow five minutes for warm-up the
unit, then set 0 Ω on decade box Rx2 and the potentiometer value on decade box Rx1 (i.e. 200 Ω) and check the
output value. It should be at low end of scale. Adjust if necessary, ZERO trimmer of the relevant channel. Set
decade box Rx1 to the potentiometer value (i.e. 200 Ω) and Rx2 to 0 Ω, check the output value that must be at full
scale and adjust, if necessary, the SPAN trimmer of the relevant channel.
Return to the low end of scale and check for shifting of calibrated value. If necessary re-adjust the output value
until it comply with the specified accuracy.
Potentiometer ranges from 100 Ω to 300 Ω are implemented without an input shunt resistor RP on the terminal
block by adjusting coarse Span and Zero as required.
Potentiometer values from 300 Ω to 100 KΩ can be accommodated by inserting RP (accuracy ±0.5%, stability 25
ppm/°C, power rating ¼ W, see 10.1.2) resistor to obtain a value near to 100 Ω, 200 Ω or 300 Ω and calibrating
ZERO an SPAN as above.
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