Burkert Type 8620 - Manual (Page 70)

mxCONTROL Type 8620
Page 70
Procedure of determining the Correction value
1. Place the Pt100 sensor and another calibrated temperature sensor ready for the comparison
measurement. Assure an uniform temperature in both sensors by applying a sufficient waiting
time.
2. Set the correction value of the corresponding Pt100 Input to "0" (in the
Configuration/Inputs/AnalogIn X menu, - password required - CodeLevel: Specialist)
3. Measure the temperature with both temperature sensors:
- TPt100 with the Pt100 sensor, connected with the „Type 8620 mxCONTROL“ (in the menu:
Process data/Inputs)
- and TCompare with the other temperature sensor used for comparison measurement.
(e.g. TPt100 = 25.1 °C and TCompare = 25.8 °C)
4. Determine the correction value due the following relation ship:
Correction value = T
Pt100
- T
Compare
(e.g. Correction value = 25,1 °C - 25,8 °C = -0,7 °C)
Assure that both values have the same engineering unit!
5. Enter the parameter "KorValue", according to the correction value determined (in the menu:
Configuration/Inputs/AnalogIn X).
The correction value must be entered in the configured unit of the corresponding Pt100 input.
Assure that the algebraic sign of the Correction value is set correctly. The new Correction value
will be enabled, if the main menu is re-entered.
6. For assurance both temperatures (as in point 3) should be measured again. Both temperature
values should have now nearly the same value. If yes, the correction of this Pt100 Input is
completed; if not continue with point 1.
A cable different than the calibration cable (with a different constant resistance) is normally
used for wiring the Pt100 sensor "in the field" with the „Type 8620 mxCONTROL“.
This leads to a falsification of the measurement, which means the measured resistance with
the used cable is lower or higher than the value measured with the calibration cable. This
falsification has to be corrected by compensation of the measured resistance.
A comparison measurement with a calibrated temperature sensor is therefore required to
determine the corresponding correction value. This correction value can be entered manually
in the configuration file or in the "Configuration" menu item.
Note: This determined correction value is valid for sensors of the same type using the
same cable.
When downloading a configuration file, the Correction value is at first internally reset to
the default value before it will be overwritten by the Correction value contained in the
configuration file.
After the change/input of the Correction value it is therefore recommended to:
- save the just changed configuration file and
- note the Correction value for future manual input.