Calibration For Level Measurement And Limit Detection - Endress+Hauser PROFIBUS Gammapilot M FMG60 Operating Instructions Manual

Commissioning
60
6.4

Calibration for level measurement and limit detection

6.4.1 Basic principles
The calibration points required for the measurement are entered in the "calibration" (*1) function
group. Each calibration point consists of a level and the associated pulse rate.
Calibration points for level measurement
A
OFF
Calibration points for level measurement; A A A A : Background calibration; B B B B : Full calibration; C C C C : Empty calibration
Background calibration
refers to the following situation:
• The radiation is switched off.
• Within the measuring range, the vessel is filled as far as possible (ideally: 100%).
The background calibration is necessary, in order to register the natural background radiation at the
mounting position of the Gammapilot M. The pulse rate of this background radiation is
automatically subtracted from any other measured pulse rate. That means: only the part of the pulse
rate which originates from the applied radiation source is taken into account and is displayed.
As opposed to the radiation of the applied source, the background radiation remains nearly constant
during the complete measurement. Therefore, it is not submitted to the automatic decay
compensation of the Gammapilot M.
Full calibration
refers to the following sitaution:
• The radiation is switched on.
• Within the measuring range, the vessel is filled as far as possible (ideally: 100%, minimum 60%).
If the vessel can not be filled to at least 60% during the calibration, the full calibration can
alternatively performed with the radiation being switched off, which is a way of simulating a filling
of 100%. In this case, the full calibration is identical to the background calibration. As the pulse rate
of the background radiation is automatically subtracted, the displayed pulse rate is about 0 cps.
Empty calibration
refers to the following situation:
• The radiation is switched on.
• Within the measuring range, the vessel is emptied as far as possible (ideally: 0%, maximum 40%).
Gammapilot M FMG 60 - PROFIBUS PA
B
ON
C
ON
L00-FMG60xxx-05-00-00-xx-001