Measuring The Temperature; Calibration; Why Calibrate - wtw pH 7110 Operating Manual

pH 7110
Stability criteria (AutoRead )
ba75925e01 07/2011
Measured parameter
pH value
Temperature
The minimum duration until a measured value is assessed as stable is the
monitored time interval. The actual duration is mostly longer.
5.1.2

Measuring the temperature

For reproducible pH measurements, it is essential to measure the temperature
of the test sample.
You have the following options to measure the temperature:
• Automatic measurement of the temperature with the temperature sensor
(NTC30 or Pt1000) integrated in the sensor.
• Measurement with an external temperature sensor.
• Manual determination and input of the temperature.
The measuring instrument recognizes whether a suitable sensor is connected
and automatically switches on the temperature measurement.
Which type of temperature measurement is active is indicated by the tempera-
ture display and the [TP] status indicator:
Resolution
Temperature of the temp.
sensor
yes 0.1 °C
- 1 °C
If you wish to measure (or calibrate) without temperature sensor, proceed as
follows:
1. Measure the current temperature of the test sample.
2. Set the temperature value with <><>.
5.2

Calibration

5.2.1

Why calibrate?

When a pH electrode is operated, its zero point (asymmetry) and slope change
with the course of time. As a result, an inexact measured value is displayed.
Time interval
15 seconds
15 seconds
Status
display indicator
[TP]
-
Stability in the time interval
Δ pH: Better than 0.02
Δ T (° C): Better than 0.3
Temp. measurement
Automatic with temperature
sensor
Manual
pH value
19