Envent Engineering Ltd. Page 19 Revision 2.4
Aperture Strip
The sample chamber has a fixed size aperture of ¼ inch which is used for
concentrations in between 1 ppm to 16 ppm.
For concentration applications below 1 ppm or above 16 ppm an aperture strip is
installed behind the window in the Sample Chamber, refer to Figure 6. These aperture
strips keep the analysis time to be approximately the same regardless of the range.
Various sizes of apertures match different measurement ranges. Table 3 shows the
aperture size according to its range.
H
S Range Aperture Strip Envent PN
50 ppb to 1 ppm ppb style 330110
1 ppm to 16 ppm None (1/4" fixed aperture size) N/A
16 ppm to 30 ppm 1/16" 330103
30 ppm to 50 ppm 1/32" 330102
50 ppm to 100 ppm Pin Holes 330100
100 ppm to 500 ppm Laser Dot 330109
Over 500 ppm Addition of a dilution panel. Consult Factory.
Table 3. Aperture Strips & Ranges
Aperture strips can be changed to accommodate for a different range application.
Refer to the table shown above to select the best option on the new concentration
application. Contact Envent Engineering Ltd to purchase an aperture strip.
Remember: gain and span values on analog outputs will have to change based on
new range application. Please re-calibrate analyzer. Refer to "H
2
S Gas Calibration" on
page 28.
The adhesive used to glue the aperture strip in its place is RTV108 Translucent
Adhesive. RTV102, RTV103, and RTV109 could also be used.
Humidifier Unit
For the H
2
S to adhere to the surface of the H
2
S Sensing tape, it needs to be
humidified. The humidifier unit helps having constant moisture content in the sample
which increases the chemical reaction on the H
2
S Sensing tape. Envent Engineering
Ltd offers a unique design of humidifiers meant to meet the requirements for
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