Metrohm 840 PC Control 5.0 / Touch Control - Manual (Page 239)

4 Parameters
PC Control / Touch Control
227
4.2 Measurements (MEAS)
The following measuring modes can be selected:
• pH (potentiometric pH measurement)
• U (potentiometric voltage measurement)
• T (temperature measurement)
• Ipol (voltametric measurement with adjustable polarization current)
• Upol (amperometric measurement with adjustable polarization volt-
age)
• Conc (concentration measurement)
• Cond (conductivity measurement, see Section 4.3).
The parameters for the measurement sequence are edited under Meas-
uring parameters .
• Signal drift (d): Drift, i.e. the alteration in the measured value per
minute that has to be reached for measured value acceptance. off
means that the measured value acceptance takes place when the
maximum waiting time has elapsed. This may be advisable if the
electrode has a very slow response.
Note!
A constant measured value is often only achieved after a certain
time, as mixing and possibly the reaction itself require a certain time.
The response time of an electrode can also increase with time, i.e.
reaching a constant measured value takes longer and longer. In such
a case drift-controlled measured value acceptance is particularly
advisable, as the measured values are only accepted when equilib-
rium has almost been achieved.
• Waiting time min. (d): The measured value is not accepted until
the minimum waiting time has elapsed, even if the measured value
drift has already been reached. The minimum waiting time is only
important for drift-controlled measurements.
• Waiting time max. (d): If the signal drift is switched off or has not
yet been reached then the measured value will be accepted after
the maximum waiting time has elapsed. If the waiting time has not
been newly entered then a waiting time that is suitable for the drift
will be calculated automatically according to the following equation:
5 0.01 Drift 150/ time Waiting + + =
• Stop measured value (d): Stops when the preset measured value
has been reached since the start of the measurement.
• Temperature (d): Manually entered measuring temperature. If a
temperature sensor is connected and temperature measurement is
set to automatic or continuous under Sensor (see Section 4.1.5)
then the temperature will be measured continuously. The value is
used for temperature compensation in pH measurements.
• Time interval MP (d): Time interval for entering a measuring point
in the list of measuring points. This list can contain max. 1000
measuring points.