Endress+Hauser Gammapilot M FMG60 - Page 48

Commissioning Gammapilot M FMG60 PROFIBUS PA
48 Endress+Hauser
Calibration points for density and concentration measurements
Function of the calibration points
In addition to the length of the irradiated measuring path, the Gammapilot M also needs the
following two parameters for density and concentration measurements:
• The absorption coefficient µ of the material measured
• The reference pulse rate I
0
2)
It calculates these parameters automatically from the pulse rates of the following calibration
points:
• Background calibration (calibration with radiation switched off)
• Up to nine calibration points for samples of various known densities
In the case of self-radiating media, the background calibration must always be
performed when the pipe is filled. A simulated calibration with an empty pipe is not
possible in this case.
OFF ON
0
1
9
A0018128
0 Background calibration
1-9 Calibration points for various densities
Two-point calibration
Two-point calibration is the calibration procedure recommended for strict accuracy
requirements over the entire measuring range. Background calibration is performed first of
all. Afterwards, the two calibration points are entered. These points should be as far apart as
possible. Once the two calibration points have been entered, the Gammapilot M calculates the
I
0
and µ parameters on its own.
2) I
0
is the pulse rate when the tube is empty. The value is significantly higher than any real pulse rates occurring
during the measurement.