16
Gas sampling and gas conditioning technology
9-3.20-MD
The correction factor is calculated:
100
Correction factor
=
(100 - O2 concentration)
This results in the following correction factor:
100
= 1.0526
(100
– 5)
For the gas mixture, the corrected total interference is therefore calculated to a good
approximation:
1.0526 x -0.1123 by volume% = -0.1182% Vol. %
The corrected total cross-sensitivity with change of prefix sign can now be used to correct the zero
point calibration. In this example the zero point would be adjusted to +0.1182% by volume.
A neglect of the cross sensitivity, in this example, would mean a relative error of about 2%.
N O T I C E !
After zero point calibration the measuring range end value must
always be calibrated!
12.2
END VALUE CALIBRATION
Before the measuring range end value is calibrated, review of the zero point must always be made.
The procedure during calibration is as follows:
Set test gas flow rate with a needle valve or flow metre to a maximum. 60 l/h. The volume
flow of the calibration gas should always correspond to the gas volume flow;
Wait approx. 30 seconds until the display has stabilised.
If necessary, adjust, using the end value potentiometer the O
2
value of the test gas,
e.g. in the case of air to 20.9% = 7.344 mA in a measuring range 0 - 100% = 4 - 20 mA.
