M&C TechGroup PMA 100 Operator's manual - Manual (Page 30)

M&C Products Analysentechnik GmbH 9-3.12-ME
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14.Measuring
The connections for sample gas inlet and outlet are located
on the back panel of the PMA100 oxygen analyser (see 8.1).
A detailed description of the menu-driven handling is given
in chapter 12.
Note!
The oxygen analyser PMA100 is suitable for continuous
measurements of oxygen concentrations in particle-free
and dry sample gases. Therefore it is recommended to use
a gas conditioning system downstream the analyser
equipped with a cooler and a particle filter.
14.1 Automatically range switch
The function of the automatically range switch is pre-selected
in menu point 12.4.2 or via the serial interface. It is recom-
mended to set unused measuring ranges to ‘0’ (see 12.4.3).
The analyser uses the suitable measuring range automatically.
Fig. 11 shows the switching between two overlapping
measuring ranges, 0 - 50Vol.-% and 30 - 40Vol.-%.
Going through the measuring ranges upward the analyser
switches exact at the range limits, in this example at 30Vol.-%
respectively 40Vol.-%.
Going down through the measuring ranges the autorange
hysteresis determines the interval switching into the next
lower range. The %-value, which is set in menu point 12.4.4,
is related to the smallest span of the switching relevant
ranges. The resultant value in Vol.-% O
2
is added to the
respected range. The switching relevant range in the
example (30 - 40Vol.-%) is 10Vol.-%. This means a
switching interval of 1Vol.-% if the adjusted hysteresis is
10%. The switching points are at 39Vol.-% respectively
29Vol.-%.
The mA-output is related to the extended measuring range 2.
This means:
29Vol.-%
- 0 mA, and
40Vol.-% - 20 mA .
14.2 Expanded measuring range
Expanded measuring ranges are selected in menu point 12.4.3.
The minimum range is 1Vol.-% O
2
. The selected mA-output
signal (see 12.4.5) is related to the respective span.
Example:
• measuring range 99 - 100Vol.-%,
• 4 - 20mA.
This means a resolution of 1/16Vol.-% O
2
per mA.
Changing pressure can cause extremely high devia-
tions using small measuring ranges without pressure
compensation.
Meas. range 1
0 - 50Vol.-%
Meas. range 2
30 - 40Vol.-%
up
down
29 30 39 40 Vol.-%
0 1,82 18,12 20 mA
Fig. 11: Automatically range switch
hysteresis 10%