Sensidyne AP-20S Instruction Manual - page 14
Doc No 360-0027-01
14
• High Concentration Gas Measurement
High concentration gas ex-
ceeding the measuring range
of the detector tube may be
sampled as follows. Collect a
volume of sample gas into a
glass syringe and dilute with
fresh air. (See photograph).
The tube reading is then mul-
tiplied by the ratio of dilution
to determine the actual con-
centration. Example: Draw
50cc of sample gas into a 100cc syringe. Complete the syringe draw
with fresh air. Take a reading and multiply by 2.
• Atmospheres With Non-ambient Pressure
If 100cc of gas is collected at a pressure that is two times
atmospheric pressure, it is equivalent to 200cc of gas col-
lected at normal atmospheric pressure. When measuring at
pressures other than normal atmospheric pressure, a pres-
sure correction is required.
A true concentration can be obtained by the following equa-
tion. However, if the tube’s concentration scale is nonlinear, a
correction error is produced. Therefore it is recommended to
collect the sample in a gas sampling bag, then measure it at
normal atmospheric pressure for more accurate readings.
When collecting gas in a high pressure atmosphere, please
note that the bag can be ruptured by the expansion of the
sample gas.
Measurement under Special conditions
Corrected value = Reading value on detector tube x 760 mmHg/
Atmospheric pressure in the measuring place [mmHg]