14
Calculations
Concentration of the permeant compound in the span outlet stream is inversely
proportional to the carrier flow rate through the chamber. It is determined using
the following equation:
ª §«
Where:
K = 24.45 / molecular weight of gas
P = permeation rate in ng/min (information included with
the permeation device documentation)
F = Chamber carrier flow (ml/min)
If the permeation rate is known for some reference temperature, the rate at a
second temperature can be estimated as follows:
log P = log P
O
+ 0.034 (T - T
O
)
Where:
P
O
= Permeation rate at reference temperature T
O
P = New permeation rate at temperature T
Certified devices should be used only at the temperature
specified on the certificate.
Using any permeation device beyond its recommended tem-
perature range could result in the destruction of the device
by explosion and/or changes in the membrane characteris-
tics. If in doubt, contact VICI Metronics with the part number
of the device to determine its maximum temperature limit.
Sample Calculation
Given:
Permeation rate: 21,000 ng/min Cl
2
@ 30°C
Carrier flow: 500 ml/min
Then:
Concentration (ppm) = K * P
F
(0.346)(21,000)
500
=
14.5
ppm
=
For zero reference measurement, remove the permeation device from the
chamber.
Summary of Contents for 340-0X
Page 9: ...5 Specifications Introduction...
Page 43: ...39 Model Number Breakdown...
