Electronic Flow Sensing
Designating gas type
59
Designating gas type
To scale the displayed flow rate value properly, one of four commonly used
gases must be designated. The appropriate gas type is selected according
to Table 4•1:
1 He (Helium) TCD
2N
2
(Nitrogen) General
3H
2
(Hydrogen) Capillary
4 Ar/CH
4
(Methane in Argon) ECD
Number Gas Type Preferred Use
Table 4-1. Defining Type of Gas to be Monitored
To select one of these gases for a particular flow channel, press:
FLOW
(
B
) to display FLOW A (or FLOW B).
1
,
2
,
3
,or
4
is then pressed, followed by
ENTER
. Upon pressing
ENTER
, the current flow rate is displayed, scaled appropriately for the
chosen gas type.
If a gas other than one of the above standard four is used, select He,
N
,H , or Ar/CH according to which one is closest in thermal
conductivity to the gas being used. Under no circumstances should any
corrosive gas be passed through the EFS.
The maximum usable range for H
is 100 ml/minute. At higher flow rates
( >100 ml/min), where a gas other than He, N
, or Ar/CH is being used,
or to ensure maximum accuracy in displayed flow rate, calibration of the
EFS may be necessary.
