AWT420 | UNIVERSAL 4-WIRE, DUAL-INPUT TRANSMITTER | OI/AWT420-EN REV. B
97
Appendix A pH solution coefficient
The solution coefficient compensates the Nernstian value for
pH measurements, and the raw voltage value for ORP
The temperature compensation factor is derived from the
following equations:
pHin dicationnernsti an ±COEF ×
mVindic ation
where:
COEF
pHnernsti an
process calibration values.
pHin dication pH value indicated on the transmitter and
proportional to the current output value.
mV millivolt value of the sensor output after
applying the factory and process calibration
values.
mVindic ation mV value indicated on the transmitter and
proportional to the current output value.
T
applying the factory and process calibration
values.
Examples of solution coefficients for pure water applications
are:
The solution coefficient for the AWT420 transmitter either adds
or subtracts a configured amount of the process variable per
Thus, an application with a process liquid that decreases in its
pH value as the temperature increases uses a positive solution
coefficient correction factor. Conversely, an application with a
process liquid that increases in its pH value as the temperature
increases uses a negative solution coefficient correction factor.
The solution coefficient affects the uncompensated process
variable for ORP analyzer types in the same manner as the pH
analyzer type.
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