M&C TechGroup PMA 50 EEX Operator's manual - Manual (Page 22)

22
Gas sampling and gas conditioning technology 9-3.15-ME
18.1 ZERO CALIBRATION
The calibraiton of the zero point is to be effected with a gas free of oxygen, eg. Nitrogen (N
2
) 5.0.
The following steps have to be executed:

Connect the flexible PVC or Viton tube with the bottle’s pressure reducer of the N
2
-zero gas
bottle;
W A R N I N G !
The pressure reducer should have a maximum outlet measuring
range of 0-1,5 bar abs. and should always be adjusted to a low
outlet pressure of max. 0,1 bar. This protects the measuring cell
against destruction due to high pressure!

First of all, open the bottle valve, then open the outlet valve of the pressure regulator;

The pressure regulator and the tubing have to be flushed for about 5 seconds;

Check adjusted control pr essure and reduce to ≤ 0,1bar if necessary then shut the outlet valve
of the pressure regulator again;

Connect the free tube end of the zero gas bottle connection with the external flow meter or, if
available, with the external calibration valve;

Open the outlet valve of the pressure regulator slowly, in order to avoid pressure peaks;

Adjust the zero gas volume flow with the needle valve of the flow meter to max. 60 l/h. The
volume flow of the calibration gas should always be adapted to the sample gas volume flow;
N O T E !
Always calibrate at the gas flow used for the measurement too.

Wait approx. 30 seconds until stabilisation of the display;

Set the range switch to 0-1% O
2
;

If necessary, adjust the zero point to 0 % via the zero point potentiometer 12 (figure 1) (with a
screw driver);

Check the analogue output signals at 0% O
2
;
Ouput signal Signal to be measured
0-1 V DC 0 V
0-20 mA 0 mA
4-20 mA 4 mA
N O T E !
Analysing a gas mixture the single components have to be checked ac-
cording to a possible cross sensitivity and to be considered for zero cali-
bration (see chapter 20).