Pressure-Programmed Carrier
Gas
Operation Using EPC System
INSTALLAnON
Chapter:
Topic:
(
i
i
1,
)
SRI 8610C GC
N
Carrier GasPressure-Programming via
r
Electronic Pressure Control
PRESSURE
PROGRAIII
FROIII
DATASYSTEIII
A-b-D
,.JiI-.+--.I
DETECTOR
COWIIINOVEN
INJECTION
PORT
EPC
1II0DULE
LOCAL
PRESSURE
CARRIER SETPOINT
GAS
IlI\SED
SYSTEIII
TOPe-
l
DATA
I
[
I
I
I
I
I
I
I
100
JBi
5Dpsi
FLOWCHART ILLUSTRATING CARRIERGAS PRESSURE PROGRAMMING ONTHE8610CGC
All SRI 8610C gas chromatographs are
equipped
with Electronic (or Pneumatic) Pressure
Control (EPC) of
all
system gases. Eachgas, from the carrier
gas,
to
the specific detector gases,
such asFIDhydrogen and FID compressed
air, in
the caseof an FID detector, arecontrolled
by
a
dedicated solid-state EPC module that electronically monitors and instantaneously adjusts the pressure
being supplied
to
theparticular feature. This electronic control facilitates extreme precision of gas
flows
to
thevarious functions. Each EPCmodule features a local, user-adjustable setpoint accessed
bya trimpot (variable potentiometer) located justabove the particular function on the "at-a-glance"
panel display. Thecarrier gas is among theseadjustable setpoints. The term "local" refers
to
the fact
that the "local"
setpoint
is setmanually at thetrimpot onthe GC chassis. As inthecase of the
column oven temperature setpoint, the carrier gaspressure setpoint may
be
set"locally" (manually on
the GCchassis), or from the computer
via
a pressure program. Created inthe same
format
asa
PeakSimple temperature program, the program signal is sent
to
the
data
system interface and
convened
to
a control voltage that canincrease, maintain, ordecrease the carrier gas pressure
automatically at theuser's command.
ThePeakSimple serial data system interface offers tworampable voltage outputs - one to
program the column oven, and the other
to
program carrier gaspressure. Outputting a 0 to5VDC
variable signal, the EPC module
will
permit an output pressure of from 0 to lllOpsi (the carrier
pressure shown is actually the column headpressure). Please note that any local setpoint value
will
be
summed
to
this signal, resulting
in
the "total" setpointvalue on the panel display. The carrier gas
pressure regulator at thegas cylinder should
be
set IOpsi higher
than
thehighest programmed carrier
gas head pressure desiredfor proper control. Ramping permits the head pressure to
be
varied, to
speed orslow theelution of peaks from theanalytical column as needed bythe application oruser.
