Measuring The Temperature; Calibration; Why Calibrate; When To Calibrate - wtw Cond 7310 Operating Manual

Conductivity
Criteria for a stable
measured value
24
The Stability control function checks whether the measured values are stable
within the monitored time interval.
Measured
parameter
ϰ
Conductivity
Temperature
The minimum duration until a measured value is assessed as stable is the mon-
itored time interval. The actual duration is mostly longer.

5.1.2 Measuring the temperature

For reproducible conductivity measurements, it is essential to measure the
temperature of the test sample.
The temperature is automatically measured by the temperature sensor
(NTC30 or Pt1000) integrated in the sensor.
The TetraCon 325, KLE 325, LR 325/01 and LR 325/001 conduc-
tivity sensors have an integrated temperature sensor.
5.2

Calibration

5.2.1 Why calibrate?

Aging slightly changes the cell constant, e. g. due to coatings. As a result, an
inexact measured value is displayed. The original characteristics of the cell can
often be restored by cleaning the cell. Calibration determines the current value
of the cell constant and stores this value in the meter.
Thus, you should calibrate at regular intervals (we recommend: every 6
months).

5.2.2 When to calibrate?

 After connecting a sensor
 Routinely within the framework of the company quality assurance
 When the cleaning interval has expired

5.2.3 Determining the cell constant (calibration in control standard)

You can determine the actual cell constant of the conductivity measuring cell
by calibrating with the control standard in the following ranges:
 0.450 ... 0.500 cm
(e.g. TetraCon 325 with a nominal cell constant of 0.475
Time interval
10 seconds
15 seconds
-1
Stability in the time interval
Δ : Better than
1.0% of measured value
Δ : Better than 0.5 °C
-1
)
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Cond 7310
06/2013