Teledyne 9110AH - Nitrogen oxides analyzer - Manual (Page 40)

TELEDYNE Model 9110AH NO
X
Analyzer Operator Manual, 01620, Rev. F
4-8
NOTE
On vacuum vs absolute pressure:
Many vacuum gauges read relative to ambient pressure, therefore
a reading of 25" of mercury (Hg) at sea level (which would give an
absolute pressure of about 5" Hg in the reaction cell) would read
only 20" Hg at high altitude sites. Therefore in this manual the vacuum
specification of 5" Hg pressure is given as an absolute pressure
- 5" Hg-A - reference against zero absolute pressure (a perfect vacuum)
thus removing ambiguities for high altitude sites.
A 47 mm diameter sample filter is provided as standard equipment to remove particulate matter
from the sample gas. It is important that the filter be maintained at regular intervals because
particulates trapped on the filter have been shown to alter the concentration of the sample. A
suggested schedule is shown in Section 8 - Maintenance. It should be noted however that more
or less frequent maintenance may be required depending on the situation.