M&C PMA Series, Instruction Manual

Page: 17 / 24

www.mc-techgroup.com PMA45K1 | 1.00.01 17
16 CALIBRATION
The preciseness of an analyzer depends to an important extent on its calibration.
NOTE!
Before executing a calibration, it must be assured that the calibration
conditions correspond to the conditions during the measurements. The
flow quantity and the barometric pressure conditions must be constant.
Under these conditions, a calibration of the analyzer becomes necessary
nearly once a week in order to keep the exactness. Should there, howev-
er, be a considerable change of the flow quantity or the barometric pres-
sure conditions, a new calibration is necessary.
During the calibration, the instrument must not be exposed to any vibra-
tions.
For the zero point calibration of the analyzer, an oxygen-free gas – in most times nitrogen (N
2
5.0) is
used as zero gas.
Regarding the sensitivity adjustment, no special test gas mixtures are necessary due to the measuring
principle and the linearly measuring ranges of the M&C O
2
analyzers. Dry and clean air is sufficient.
For measuring value concentrations of > 40 % O
2
, it may be recommendable to make a calibration
with a respective test gas.
16.1 ZERO POINT ADJUSTMENT
• Connect a flexible PVC or Viton tube with the pressure reducer of the N
2
zero gas bottle.
The pressure reducer should have got an output range of adjustment of max. 0 – 1.5 bar.
• Open the cylinder valve first and then open the closed output valve of the pressure con-
troller. Purge the pressure controller including the tubes for approx. 5 seconds.
• Check the adjusted pressure and reduce it if necessary to ≤ 0.1 bar, then close the output
valve of the pressure controller again.
• Connect the free tube end of the zero gas bottle connection to the gas inlet of the analyzer
or – if existing – to the external calibration valve.
• Open slowly the pressure controller output valve in order to avoid pressure peaks.
•
Adjust the flow at approx. 50 l/h on the flowmeter.
NOTE!
Always calibrate with the same gas quantity that is taken for measure-
ment.
•
Wait approx. 20 - 30 seconds until the indication is stable.
•
Turn the measuring range selector switch ( 4 , see figure 2) in position 2.5 %.
•
If necessary, adjust the zero point with a screw driver to exactly 0 % O
2
on the zero point
potentiometer ( 5 , see figure 2) on the bottom side of the housing.
•
Check the signals of the recorder output at 0.0% O
2
:
Recorder output signal Measured
value
0-10 V 0 V
0-20 mA 0 mA
4-20 mA 4 mA