VICI Dynacalibrator 345 - Manual (Page 19)

15
Basic Operation
Important Permeation Device Considerations
• If more than one tube is to be used in the oven at the same time, order all the
tubes with permeation rates given at the same temperature.
• Certified permeation devices should be used only at the temperature specified
on the certificate.
• Using any permeation device beyond its recommended temperature range
could result in the destruction of the device by explosion and/or changes
in the membrane characteristics. If in doubt, contact VICI Metronics or their
authorized representative with the part number of the device to determine its
maximum temperature limit.
Manual Mode
Concentration of the permeant compound in the span outlet stream is inversely
proportional to the carrier flow rate through the chamber. In the Manual mode
of operation, use the following formula to establish the dilution flow rates to
achieve the desired concentration.
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) factory set @ 100 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
Sample Calculation
Given:
Permeation rate: 21,000 ng/min Cl
2
@ 30°C
Carrier flow: 500 ml/min
Then: Concentration (ppm) = (K*P)/500= 14.5 ppm
For zero reference measurement, remove the permeation device from the chamber.
Once the calculations have been rendered, enter the Manual mode of operation
by select ng the “Manual” tab on the display controller. Enter the value for Temp
Set point and Diluent Flow Set point (Figure 9) To enter a new value, touch in-
side the white area of the field and use the up/down controller to alter the value.
Select “OK” when finished.