APPENDIX A
255-100C-4 WIRING DIAGRAM
JDC
09-20-2018
255-100C-4
Calibration Procedure
890-0020-01
1 2
White - Signal
Black - Reference
Shield - Earth ground
Red - Excitation
Analog Output
Evaporation Gauge
Model 255-100
mA COM
R28 GAIN
R26 OFFSET
20°
19.1 mA
4.0 mA
Dead Band
1) Connect a 9V or 12V battery and meter as shown.
2) Rotate the gear until the lowest mA reading is obtained. Adjust R26 OFFSET to 4.00 ±0.080 mA.
3) Rotate the gear counter-clockwise. The output will rise gradually until the dead band
is reached and then jump suddenly to 26-28 mA. Back off slightly to get out of the dead band
and adjust R28 GAIN to 19.1 ±0.080 mA.
4) There is a small interaction between the GAIN and OFFSET pots, so verify the lowest mA reading
is still 4.00 ±0.080 mA.
