Pressure-Programmed Carrier
Gas
Operation Using EPC System
INSTALLAnON
Chapter:
Topic:
(
i
i
1,
)
PRESSURE
PROGRAIII
FROIII
DATASYSTEIII
SRI 8610C GC
EPC
1II0DULE
LOCAL
PRI'SSlIRE
CARRIER SETPOINT
GAS
i
Carrier Gas Pressure-Programming via
r
Electronic Pressure Control
COWIIINOVEN
INJECTION
PORT
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DETECTOR
A·b·D
100
JBi
TOPC-8I\SED
DATASYSTEIII
5Dpsi
FLOW CHART ILLUSTRATING CARRIER GAS PRESSURE PROGRAMMrn"G ON THE 8610C GC
All SRI 8610C gas chromatographs are
equipped
with Electronic (or Pneumatic) Pressure
Control (EPC) of all system gases. Each gas, from the carrier gas,
to
the specific detector gases,
such as FID hydrogen and FID compressed air,
in
the case of an
Fill
detector, are controlled
by
a
dedicated solid-state EPC module
that
electronically monitors and instantaneously adjusts the pressure
being supplied
to
the particular feature. This electronic control facilitates extreme precision ofgas
flows
to
the various functions. Each EPC module features a local, user-adjustable setpoint accessed
by
a trimpot (variable potentiometer) located just above the particular function on the "at-a-glance"
panel display. The carrier gas is among these adjustable setpoints. The term "local" refers
to
the fact
that the "local" setpoint is set manually at the trimpot on the GC chassis. As in the case of the
column oven temperature setpoint, the carrier gas pressure setpoint may
be
set "locally" (manually on
the GC chassis), or from the computer
via
a pressure program. Created in the same format as a
PeakSimple temperature program, the program signal is sent to the data system interface and
convened
to
a control voltage that can increase, maintain, or decrease the carrier gas pressure
automatically at the user's command.
The PeakSimple serial data system interface offers two rampable voltage outputs - one to
program the column oven, and the other to program carrier gas pressure. Outputting a 0
to
5VDC
variable signal, the EPC module
will
permit an output pressure of from 0 to lOOpsi (the carrier
pressure shown is actually the column head pressure). Please note that any local setpoint value
will
be
summed
to
this signal, resulting
in
the "total" setpoint value on the panel display. The carrier gas
pressure regulator at the gas cylinder should
be
set IOpsi higher
than
the highest programmed carrier
gas head pressure desired for proper control. Ramping permits the head pressure
to
be
varied,
to
speed or slow the elution of peaks from the analytical column as needed by the application or user.
