TPS miniCHEM-pH, Руководство пользователя, Страница: 15 / 28

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3.7 Calibrating the 4 to 20mA Output
The 4 to 20mA output of the mini CHEM -pH 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 -pH 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 -pH 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 14.00.
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 14.00, calculate the expected output level and use this for
calibration. Remember that the difference between 0 and 14 pH is to be made
16mA.
3.8 CMRR Control
The Common Mode Rejection Ratio (CMRR) is factory-set with the CMRR
trimmer.
DO NOT ATTEMPT TO ADJUST THE CMRR TRIMMER.
If this trimmer is accidentally re-set, the unit would best be returned to the factory
for re-calibration.
3.9 Factory Config. Jumpers
The Factory Config. jumpers are factory set, and must not be altered. In case
any of these jumpers are changed or removed, re-fit them as shown below. The
mini CHEM -pH must be switched OFF before changing jumper settings.
Factory
Config.