Samson 3767 - Page 45

EB8355-2EN 45
Operation
Zeropointadjustment
1. Use the input signal of the positioner to
move the valve to closed position (valve
CLOSED,travel0%).
2. The ammeter must now indicate approx.
4mA.
3. Correct smaller deviations at the ZERO
potentiometer until the meter shows ex-
actly4mA.
Forlargerdeviationsthatcannotbecor-
rected using the potentiometer (adjust-
mentrangeofapprox.20turns),setthe
switches 1 and 2 to indicate an mA val-
ue which is within the adjustment range
of the ZERO potentiometer.
4. Setthezeropointtoexactly4mAusing
the ZERO potentiometer.
Adjustingthespan
1. Use the input signal of the positioner to
move the valve to closed position (valve
CLOSED,travel100%).
2. The ammeter must now indicate approx.
20mA.
3. Correct smaller deviations at the SPAN
potentiometer until the meter shows ex-
actly20mA.Ifdeviationsaretoohigh,
set the switches 3 and 4 to indicate an
mA signal which is within the adjustment
range of the SPAN potentiometer.
4. Turn the SPAN potentiometer until the
ammetershowsexactly20mA.
Since the zero point and span have a
mutualinuenceoneachother,repeat
thecorrectionprocedureatbothpotenti-
ometersuntilbothvaluesarecorrect.