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Journal ArticleDOI

A Microcomputer System for Real-Time Monitoring and Control of Gas Chromatographs

01 Jun 1976-Journal of Chromatographic Science (Oxford University Press)-Vol. 14, Iss: 6, pp 274-278

TL;DR: A microcomputer system based on the Intel 8008 microprocessor has been developed to perform real-time, on-line data acquisition and analysis of gas Chromatographic data, and to control sampling and operation of the gas chromatograph.

AbstractLBL-4138 A microcomputer system based on the Intel 8008 microprocessor has been .developed to perform real-time, on-line data acquisition and analysis of gas chromatographic data, and to control sampling and operation of the gas chromatograph. Real-time analysis is achieved by the novel method of interleaving subprograms for the sequential data acquisition and reduction steps, thereby minimizing memory requirements. The system contaiils a real-time clock for signal timing,and interfaces to a teletype and digital volt meter. A digital-to-analog converter is used to control the temperature of the gas chromatographic column, while a matrix of relays is able to actuate sampling values.

Summary (1 min read)

The Microcomputer System

  • A microcomputer system based on the Intel 8008 microprocessor was constructed using the bin-oriented modular approach developed at the .
  • Logic cards supporting integrated circuits are connected together by a forty-wire bus whichcontrols input, output, memory storage and timing functions.
  • An important feature of the microcomputer controller is the direct digital control (DDC) of the column heater.
  • A method offering greater precision and low cost is the combination of a digitally controlled timer with a solid-state >triac .
  • The counter starts a count-up sequence until the carry bit is set, whereupon the counter overflows in a time less than 1/120 sec (half-cycle period).

Experimental

  • The microcomputer system was experimentally tested in separate process-control and analytical studies.
  • The program behavior was throughly tested for timing requirements and for performance quality using test routines in conjunction with a Beckman GC-2A gas chromatograph with a thermal conductivity detector.
  • A first-order digital filter was implemented for noise filtering of both the gas chromatograph detector signal and for the column heater control algorithm.
  • The noise reduction of the detector input was achieved by reading the amplified detector signal n (typically 3 < n < 5) times in succession and then using the weighted mean (1) where f. -1 , as the input for analysis and control calculations.
  • 1 . Noise filtering of the columri heater temperature was achieved with filter state equation, where the gain, f 1 , was given the value 0.7.

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Lawrence Berkeley National Laboratory
Recent Work
Title
A MICROCOMPUTER SYSTEM FOR REAL-TIME MONITORING and CONTROL OF GAS
CHROMATOGRAPHS
Permalink
https://escholarship.org/uc/item/9nz444kn
Author
Donaghey, L.F.
Publication Date
1976-04-01
eScholarship.org Powered by the California Digital Library
University of California

' '
u J
Submitted
to
Journal
of
Chromatographic
Science
LBL-4138
Rev.
Preprint
C.
)
A
:MICROCOMPUTER
SYSTEM
FOR
REAL-TIME
MONITORING
AND
CONTROL
OF
GAS
CHROMATOGRAPHS
L.
F.
Donaghey,
G.
M.
Bobba,
and
D.
Jacobs
;,
: ;
~
April
1976
Prepared
for
the
U.
S.
Energy
Research
and
Development
Administration
under
Contract
W
-7405-ENG
-48
For
Reference
Not
to
be
taken from this room
. J
'-\
1
L~
\'
'.
~
.•
'
i_
~
••
:

.---------LEGAL
NOTICE---------
..
This report was prepared
as
an
account
of
work sponsored
by
the
United
States Government. Neither the United States nor the United
States Energy Research and Development Administration, nor any
of
their employees, nor any
of
their contractors, subcontractors, or
their employees, makes any warranty, express or implied,
or
assumes
any legal liability
or
responsibility for the accuracy, completeness
or usefulness
of
any information, apparatus, product
or
process
disclosed,
or
represents that its use would
not
infringe privately
owned rights.

DISCLAIMER
This document was prepared
as
an account
of
work sponsored by the United States
Government. While this document is believed
to
contain correct information, neither the
United States Government nor any agency thereof, nor the Regents
of
the University
of
California, nor any
of
their employees, makes any warranty, express or implied, or
assumes any legal responsibility for the accuracy, completeness, or usefulness
of
any
information, apparatus, product, or process disclosed, or represents that its use would not
infringe privately owned rights. Reference herein to any specific commercial product,
process, or service by its trade name, trademark, manufacturer, or otherwise, does not
necessarily constitute or imply its endorsement, recommendation,
or
favoring by the
United States Government or any agency thereof, or the Regents
of
the University
of
.
California. The views and opinions
of
authors expressed herein do not necessarily state or
reflect those
of
the United States Government or any agency thereof or the Regents
of
the
University
of
California.

0 0
A
Microcomputer
System
for
Real-Time
Monitoring
and
Control
of
Gas
Chromatographs
L.
F.
Donaghey,
G.
M.
Bobba
and
D.
Jacobs
LBL-4138
REVISED
Materials
andMolecular
Research
Division,
Lawrence
Berkeley
Laboratory
and
Department
of
Chemical
Engineering,
University
of
California,
Berkeley,
California
94720
April,
1976
Abstract
Microcomputer
systems,
based
on
the
Intel
8008
and
8080
microprocessors,have
been
developed
to
perform
real-time,
on-line
data
acquisition
and
analysis
of
gas
chromatographic
data
and
to
control
sampling
and
operation
of
the
gas
chromatograph.
Real-time
analysis
is
achieved
by
the
novel
method
of
interleaving
subprograms
for
the
sequential
data
acquisition
and
reduction
steps,
thereby
minimizing
memory
requirements.
The
systemcontains
a
real-time
clock
for
signal
timing,
and
interfaces
to
a
teletype
and
di~ital
volt
meter.
An
automated
triac
controller
is
used
to
control
the
temperature
of
the
gas
chromatographic
column,
while
a
matrix
of
relays
is
able
to
actuate
sampling
values.

Citations
More filters

Journal ArticleDOI
TL;DR: The study showed that the real-time microcomputer system gave peak areas which were lower than the off-line results by less than 0.6 percent, and the difference was shown to arise from truncation error in the double-precision octal mathematical subroutines, and to error in a baseline at the peak-end.
Abstract: The real-time performance of a microcomputer system designed for dedicated control of gas chromatography and real-time analysis was studied to determine operating characteristics and accuracy of the peak-area integration algorithm. The software program developed to obtain peak areas used statistical criteria for the detection of the start, maximum value, and end of a chromatographic peak. The accuracy of the system was tested with propane-helium mixtures and by comparison to results obtained with off-line data reduction. The study showed that the real-time microcomputer system gave peak areas which were lower than the off-line results by less than 0.6 percent. The difference was shown to arise from truncation error in the double-precision octal mathematical subroutines, and to error in the assignment of a baseline at the peak-end.

7 citations


01 Sep 1975
TL;DR: A new microcomputer system allows many gas chromatographs to share the microcomputer facilities, thus greatly expanding the system capacity at a low cost, without affecting the singl,e-user performance.
Abstract: A microcomputer system for on-line, real-time I simultaneous analysis and control of multiple gas· chromatographs is'described. LBL-4139 The system, incorporating the INTEL 8080 microprosser, is an improved version of an INTEL-8008-based·microcomputer system developed by the authors for real-time analysis and· control of a gas chromatograph. The new microcomputer system allows many gas chromatographs to share the microcomputer -· facilities, thus greatly expanding the system capacity at a low cost, without affecting the singl,e-user performance. This new achievement has been made possible by a high-speed central processing unit in the microcomputer and by special-purpose hardware and software developments. A new feature incorporated in the system is a parallel-asynchronous interface for teletype output operations. The interface enables simultaneous analytical and output functions without interfering with the timing of the data sampling process.

2 citations


References
More filters

Journal ArticleDOI
TL;DR: The study showed that the real-time microcomputer system gave peak areas which were lower than the off-line results by less than 0.6 percent, and the difference was shown to arise from truncation error in the double-precision octal mathematical subroutines, and to error in a baseline at the peak-end.
Abstract: The real-time performance of a microcomputer system designed for dedicated control of gas chromatography and real-time analysis was studied to determine operating characteristics and accuracy of the peak-area integration algorithm. The software program developed to obtain peak areas used statistical criteria for the detection of the start, maximum value, and end of a chromatographic peak. The accuracy of the system was tested with propane-helium mixtures and by comparison to results obtained with off-line data reduction. The study showed that the real-time microcomputer system gave peak areas which were lower than the off-line results by less than 0.6 percent. The difference was shown to arise from truncation error in the double-precision octal mathematical subroutines, and to error in the assignment of a baseline at the peak-end.

7 citations


01 Sep 1975
TL;DR: A new microcomputer system allows many gas chromatographs to share the microcomputer facilities, thus greatly expanding the system capacity at a low cost, without affecting the singl,e-user performance.
Abstract: A microcomputer system for on-line, real-time I simultaneous analysis and control of multiple gas· chromatographs is'described. LBL-4139 The system, incorporating the INTEL 8080 microprosser, is an improved version of an INTEL-8008-based·microcomputer system developed by the authors for real-time analysis and· control of a gas chromatograph. The new microcomputer system allows many gas chromatographs to share the microcomputer -· facilities, thus greatly expanding the system capacity at a low cost, without affecting the singl,e-user performance. This new achievement has been made possible by a high-speed central processing unit in the microcomputer and by special-purpose hardware and software developments. A new feature incorporated in the system is a parallel-asynchronous interface for teletype output operations. The interface enables simultaneous analytical and output functions without interfering with the timing of the data sampling process.

2 citations