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3.7 Calibrating the 4 to 20mA Output
The 4 to 20mA output of the
mini
CHEM
-DO
2
is factory calibrated. However,
TPS has provided calibration controls for the 4mA and 20mA points in case this
requires adjustment in the field. Only a limited amount of adjustment is available,
as the
mini
CHEM
-DO
2
is designed for 4 to 20mA output for the full scale of the
instrument.
Calibrating the 4 to 20mA output…
1. Connect a Digital Milliamp Meter between terminals 7 and 8.
2. Switch the
mini
CHEM
-DO
2
to
SET LIMIT
.
3. Adjust the
LIMIT
control until the display reads 0.00.
4. Adjust the
ZERO/4mA
trimmer in the terminal area until the Digital Milliamp
Meter reads 4 mA.
5. Adjust the
LIMIT
control until the display reads 19.99 ppM or 199.9 %
Saturation.
6. Adjust the
SPAN/20mA
trimmer in the terminal area until the Digital
Milliamp Meter reads 20 mA.
In the event that the
LIMIT
control does not have sufficient adjustment to
reach 0.00 or 19.99/199.9, calculate the expected output level and use this
for calibration. Remember that the difference between 0 and 19.99/199.9 is
to be made 16mA.
