Yokogawa EXA PH202 2-Wire pH/ORP Analyzer User Manual

Page 64

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IM12B07D02-01E

Parameter setting 5-13

5-3-2. Temperature compensation and measuring functions.

Code 10 *T.SENS

Selection of the temperature compensation sensor. The default selection is

the Pt1000 Ohm sensor, which gives excellent precision with the two wire

connections used. The other options give the flexibility to use a very wide

range of other pH sensors.

Code 11 *T.UNIT

Celsius or Fahrenheit temperature scales can be selected to suit user

preference.

Code 12 *T.ADJ

With the process temperature sensor at a stable known temperature, the

temperature reading is adjusted in the main display to correspond. The

calibration is a zero adjustment to allow for the cable resistance, which will

obviously vary with length.

The normal method is to immerse the sensor in a vessel with water in it,

measure the temperature with an accurate thermometer, and adjust the reading

for agreement.

Code 13

*T.COMP Process compensation automatically allows for changes in the pH or ORP

of the process with temperature. The characteristic of each process will be

different, and the user should determine if this feature is to be activated, and

what compensation figure to choose.

The compensation is given in pH per 10 °C or mV per 10 ºC.

The standard temperature is 25°C (fixed value) in setting the temperature

compensation.

Example:

For pure water with an alkali dose, (e.g. boiler feed water)

a coefficient of approx. 0.35pH can be expected. However,

applications vary and a simple test will determine what if any

coefficient is suitable for the process.

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