<s>
Originally	O
the	O
gas	B-Application
flow	I-Application
computer	I-Application
was	O
a	O
mechanical	O
(	O
1920s	O
technology	O
)	O
or	O
later	O
a	O
pneumatic	O
or	O
hydraulic	O
computing	O
module	O
(	O
1940s	O
technology	O
used	O
to	O
the	O
early	O
1990s	O
but	O
still	O
available	O
from	O
a	O
number	O
of	O
suppliers	O
)	O
,	O
subsequently	O
superseded	O
in	O
most	O
applications	O
by	O
an	O
electronic	O
module	O
,	O
as	O
the	O
primary	O
elements	O
switched	O
from	O
transmitting	O
the	O
measured	O
variables	O
from	O
pneumatic	O
or	O
hydraulic	O
pressure	O
signals	O
to	O
electric	O
current	O
as	O
explosion-proof	O
(	O
1960s	O
technology	O
to	O
present	O
)	O
)	O
and	O
then	O
intrinsically	O
safe	O
(	O
1970s	O
to	O
present	O
)	O
transmitters	O
(	O
with	O
low-power	O
transistor	O
circuitry	O
)	O
became	O
available	O
,	O
that	O
simply	O
provided	O
a	O
dedicated	O
gas	B-Application
flow	I-Application
computer	I-Application
function	O
.	O
</s>
<s>
Today	O
"	O
gas	B-Application
flow	I-Application
computers	I-Application
"	O
as	O
such	O
have	O
become	O
uncommon	O
,	O
since	O
gas	O
flow	O
computing	O
is	O
a	O
subfunction	O
of	O
a	O
data	O
acquisition	O
and	O
control	O
program	O
implemented	O
with	O
programmable	B-Architecture
logic	I-Architecture
controller	I-Architecture
(	O
PLCs	O
)	O
and	O
remote	B-Device
terminal	I-Device
unit	I-Device
(	O
RTUs	O
)	O
;	O
with	O
the	O
rise	O
of	O
smart	O
transmitters	O
in	O
the	O
early	O
1980s	O
,	O
these	O
functions	O
have	O
also	O
been	O
incorporated	O
within	O
the	O
field	O
transmitters	O
themselves	O
.	O
</s>
<s>
The	O
"	O
gas	B-Application
flow	I-Application
computer	I-Application
"	O
senses	O
a	O
mixed	O
"	O
dry	O
"	O
gas	O
stream	O
flow	O
rate	O
plus	O
gas	O
temperature	O
and	O
pressure	O
.	O
</s>
<s>
Therefore	O
the	O
gas	B-Application
flow	I-Application
computer	I-Application
also	O
requires	O
the	O
entry	O
of	O
mole	O
percentages	O
for	O
each	O
gas	O
component	O
.	O
</s>
<s>
These	O
values	O
in	O
joules	B-Language
(	O
or	O
calories	O
or	O
Btus	O
)	O
are	O
typically	O
built	O
into	O
the	O
gas	B-Application
flow	I-Application
computer	I-Application
algorithm	O
.	O
</s>
<s>
In	O
summary	O
the	O
gas	B-Application
flow	I-Application
computer	I-Application
requires	O
approximately	O
30	O
initial	O
input	O
parameters	O
in	O
conjunction	O
with	O
"	O
near	O
realtime	O
"	O
gas	O
flow	O
,	O
pressure	O
and	O
temperature	O
sensing	O
.	O
</s>
<s>
In	O
addition	O
to	O
providing	O
volumetric	O
,	O
mass	O
and	O
energy	O
flow	O
data	O
,	O
the	O
gas	B-Application
flow	I-Application
computer	I-Application
also	O
provides	O
date	O
and	O
time	O
,	O
instantaneous	O
,	O
hourly	O
and	O
daily	O
data	O
.	O
</s>
<s>
The	O
gas	B-Application
flow	I-Application
computer	I-Application
typically	O
stores	O
date/time	O
stamped	O
volume	O
records	O
in	O
RAM	O
for	O
up	O
to	O
35	O
days	O
in	O
order	O
to	O
provide	O
sufficient	O
time	O
for	O
a	O
host	O
system	O
to	O
retrieve	O
the	O
records	O
as	O
well	O
as	O
to	O
allow	O
time	O
for	O
human	O
intervention	O
if	O
this	O
retrieval	O
fails	O
to	O
occur	O
.	O
</s>
