Environnement AS32M, Technical Manual, Page: 96 / 186

Environnement
S.A
AS32M
Duplication prohibited
DECEMBER 2013
3–58
3.4.3 CHECKING OF ONE SCALE POINT
3.4.3.1 Equipment required
Scale point

NO
2
cylinder, the concentration of which is lower than 1 ppm (between 0.5 and 1 ppm) and is
connected to the span gas inlet of the analyzer.

Internal permeation bench equipped with a NO
2
tube (connected to the span gas inlet of the
analyzer). The concentration generated by the permeation bench is recorded on the test report.

Portable calibrator (VE3M type) equipped with a NO
2
tube and connected to the span gas inlet of
the analyzer.
NOTE :
If the analyzer is equipped with an internal permeation bench, the sample inlet must be
used to connect the reference gas cylinder or the portable calibrator.
3.4.3.2 Procedure
Scale point checking
By pressing the [Span] or [Sample] key, select the gas inlet where the span gas is connected and wait
for the measurement to stabilize. The measurement obtained must be compared to the concentration
generated by the equipment used, taking into account the accuracy of this equipment.
If the difference between the span gas value and the reading is higher than + 5 %, it is necessary to
carry out a span adjustment. Refer to section 0 «
MEASUREMENT

Instantaneous »
.
3.4.3.3 Use of automatic cycles
For programming cycles, refer to section 3.3.3.3 «
SPAN

Cycles »
.
Calibration cycle
The device for scale point generation is permanently linked to the span gas inlet of the analyzer. The
NO
2
titration has to be lower than the full scale of the range used in measurement. The recommended
timing for the check is 1200 seconds.
3.4.4 TWO-POINT CALIBRATION
3.4.4.1 Devices

Zero air:
It is possible to use the zero air filter or, for better accuracy, a zero air generator with molecular
sieve or a synthetic air cylinder (mixture of 80 % N
2
and 20 % O
2
). These devices are linked to the
sample or span gas inlets of the analyzer.

Scale point:
Cylinder of NO
2
, titrated at approximately 80 % of full scale of the measurement range used
(ac 1 %). For reasons of gas mixture stability, the use of a high-concentration (10 ppm or
more) cylinder is preferred. In this case, a dilution system (MGC101 type) has to be used to
decrease the gas concentrations to the usable range.