Span calibration – M&C TechGroup PMA 20 Operator's manual User Manual
Page 19
19
Gas sampling and gas conditioning technology
9-3.5.1-ME
The correction factor is calculated as follows:
100
Correction factor
=
(100
– O
2
-concentration)
It is incidental:
100
= 1,0526
(100
– 5)
For the gas mixture the rectified sum cross sensitivity then is calculated in good approximation:
1,0526 x -0,1123 Vol.% = -0,1182 Vol.%
The rectified sum cross sensitivity with change of sign now can be used for the correction of the
zero calibration. In this case zero had to be adjusted at +0,1182 Vol.%.
In case the cross sensitivities should be ignored in the above mentioned example, this would re-
sult in a relative error of approximately 2%.
N O T E !
After zero calibration the span has to be calibrated too.
16.2
SPAN CALIBRATION
Before span calibration a finished zero calibration is necessary.
Turn the measuring range selection switch to the measuring range in which the calibration
should be done. In case of measuring value concentrations <30% O
2
a calibration with dry
clean air in the range of 30% O
2
is recommended. Turn the measuring range selection
switch to 30%. In case of measuring value concentrations >40% O2 a calibration in the
100% range with adequate test gas is recommended. Turn the measuring range selection
switch to 100%.
Connect a flexible PVC- or FEP-hose with the pressure reducer of the N
2
-zero-gas bottle.
The pressure reducer should have an output control range of max. 0
– 1,5 bar abs..
C A U T I O N !
The outlet pressure is only allowed to be adjusted at max. 0,1 bar. Other-
wise the measuring cell of the analyser will be destroyed.
Open the bottle valve and than the closed pressure reducer outlet valve and purge the
pressure reducer and the complete hose line for approximately 5 sec. the pressure reduc-
er and the complete hose line.
Check the adjusted control pressure and reduce if necessary to
≤ 0,1bar, then shut off the
pressure reducer valve again.