Mechanical Zero Point Adjustment; Figure 9 Transmitter Unit For Mechanical Zero Point Adjustment - M&C PMA Series Instruction Manual

23.2

MECHANICAL ZERO POINT ADJUSTMENT

The mechanical zero point adjustment has to be done as described in the following.
1 LED
2 Temperature fuse (cut-off at 72 °C [161.6 °F])
3 Sample gas heating coil
4 Fastening screw photo cell
Figure 9 Transmitter unit for mechanical zero point adjustment

Before switching on the analyzer, set the range selector to 30 %. Check the zero point of the analog display
and adjust it if necessary to 0 % via the adjustment screw below the digital display;

Switch on the analyzer via the external switch. Normally, the analog display will indicate a value of 21 % oxy-
gen, because the cell is filled with ambient air;

The warming up is indicated by the permanently lit heating control-LED
analyzer; after approx. 30 minutes, the flashing display signalizes that the required operating temperature has
been reached;

Set the potentiometer for zero point and full scale value in the middle position; you can do this by turning
the potentiometer with a screw driver fully to the left and then turn it five turns back to the right;

Charge the analyzer with a zero gas volume flow of approx. 40 l/h;

With a precise adjustment of the zero point, the analog display should indicate 0.0 vol% oxygen;
If this does not happen, please execute the following steps:

Open the housing of the analyzer (see chapter 23.1);

Remove carefully the isolating cap of the transmitter unit; now, all screws of the photo cell holder are visible
(see Figure 9);

Set the range switch to 3 %;

Turn the adjustment screw 6 (see Figure 9) of the photo cell as long clockwise or anticlockwise as on the dis-
play appears a value of nearly 0.0 vol% oxygen;

After the mechanical zero point adjustment, the fixing screw of the photo cell holder 4 must be tightened
again;

Now, the zero point adjustment has been done;

Place carefully the isolating cap on the analyzer and close it according to chapter 23.1.
36
5 Heater element
6 Adjustment screw photo cell
7 Measuring cell
8 Photo cell
PMA 50 EX | 1.01.04
(13 Figure 1) in the front plate of the
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