Yokogawa EXA PH202 2-Wire pH/ORP Analyzer - Manual (Page 138)

IM 12B0702-01E
11-16 Appendix
11-7. Temperature coefficient (*T.COEF) setting at the time of conversion to reference temperature
This is settable only when conversion to reference temperature (*T.COMP) is set to 1 (ON) at service
level code No. 13. If turned to 0 (OFF), this menu will be skipped.
For conversion to reference temperature (reference temperature : 25°C ), set the coefficient between
-1.00 and 1.00 [(pH/ °C) x10]. The coefficient is set 0.00 ((pH/ °C)x10] at the time of shipment. Calculate
the solution temperature coefficient using the following equation by measuring the pH values of a meas-
ured constant-solute concentration liquid at different temperatures. That is, the temperature coefficient
to be entered in the pH converter is the value expressed in [ΔpH/ΔT] x 10. This value matches the pH-
value which varies in proportion to the measured solution temperature change of 10°C.
(pH at the higher temp.) - (pH at the lower temp.)
(the higher temp.) - (the lower temp.)
× 10 = Temp. coefficient α [(pH / °C)×10]
ΔpH
ΔT ×10 =
Equation 6-1E.eps
For example, if the pH value is 9.20 at 20.0°C, and pH 8.92 at 30.0°C, the temperature coefficient will be
as calculated below.
8.92 [pH] - 9.20 [pH]
30.0 [°C] - 20.0 [°C] × 10 = -0.28 [(pH / °C)×10]
α =
Equation 6-1E.eps
Besides the pH value displayed in the data area when conversion to reference temperature is performed
is as shown below using the set temperature coefficient α.
(Displayed pH value) = (Measured pH value) - α x (T-25 )/10