Brooks Instrument 5860i - Manual (Page 34)

Brooks ® Model 5860 i
4-10
Section 4 Maintenance
Installation and Operation Manual
X-TMF-5860i-MFM-eng
Part Number: 541B110AAG
November, 2008
Example:
The desired gas is Silane (SiH
4
).
The desired full scale flow rate is 200 sccm.
Sensor conversion factor is 0.679 from Table 4-3.
Air equivalent flow = 200/0.679 = 294.5 sccm Nitrogen.
In the example above a size P restrictor would be selected.
NOTE: If the calculated flow rate is such that two different size restrictors
could be used, always select the larger size.
If a mixture of two or more gases is being used the restrictor selection
must be based on the nitrogen equivalent flow rate of the mixture.
Example:
The desired gas is 20% Helium (He) and 80% Chlorine (Cl) by volume.
The desired full scale flow rate of the mixture is 20 slpm.
Sensor conversion factor for the mixture is:
Nitrogen equivalent flow = 20/.901 = 22.20 slpm Nitrogen.
In this example a size 4 wire mesh assembly would be selected.