Response Times And Temperature Compensation - Testo 252 Bedienungsanleitung

Response times and temperature compensation

Response times
The more the temperature of the measuring
connector differs from that of the object of
measurement, the longer the measured value from
the pH electrode takes to stabilise. Isothermic
conditions are therefore favourable for accurate
measurements. The storage of pH measuring
connectors in the recommended storage solution
contributes towards quick response times.
Temperature compensation
Two important factors influence the behaviour of
temperature in pH measuring technology:
a) the change in the pH value with the
temperature
and
b) the temperature dependancy of the pH
electrode itself.
On a)
The change in the pH value of the measuring
solution cannot be compensated with the
temperature; it should be measured.
On b)
The determining factor is the temperature-
dependent change in voltage at the pH membrane.
It is calculated according to the so-called Nernst
equation and effects the slope S of the pH
electrode.
When the temperature increases, the slope S
increases. This correction is automatically carried
out by the instrument and thus forms the basis of
the temperature compensation (after calibration,
the slope S
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displayed for better comparison).
The testo 252 enables the user to measure the
temperature value for temperature compensation
via a connected temperature sensor (integrated in
the pH electrode or separately connected*) or to
enter the value manually.
* the use of surface probes is not permissible here.
pH measurement
based/calculated on 25 °C is
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