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3.7
CUSTOM SOFTWARE
Custom software may be developed by the user to receive and archive
RheoVac
data into a computer
system. The electronics has a serial data protocol of 9600 baud, no parity check, eight data bits and one
stop bit (i.e., 9600,N,8,1). Each transmitted group of data is sent in a standard ASCII coded format
representing each process variable value, instrument identification and status information.
The data stream consists of 13 fields, followed by a carriage return <RETURN>. The first ten fields,
nine bytes each, are the process variables. Following the process variables are the
RheoVac
serial
number, nine bytes, the process identification tag number, 15 bytes, and the
RheoVac
system status,
seven bytes. The data stream is then ended by a single <RETURN> byte (ASCII code 13). The total
number of bytes transmitted in each data stream is 122 bytes per probe including the trailing
<RETURN>. This data group is sent approximately once every three seconds. Table V shows the field
names and number of bytes in one data stream.
TABLE V.
Serial Output Data Stream**
Actual
V o lu m e
Flow
(A C FM )
Total
Mass
Flow
(lbs/hr)
Water
Vapor
Flow
(lbs/hr)
RheoVac
Pressure
("Hg abs)
Water
Vapor
Sp. V ol.
(ft
3
/16)
W ater to
Air Mass
Ratio
(lb/lb)
Relative
Saturation
( %)
H
2
O
Partial
Pressure
("Hg abs)
Air F lo w
In-Leak
(S CF M )
Probe
Temp.
( ° F)
Instr.
Serial
Numbe
r
ID
Tag
No.
Status
T e rm .
< C R >
9
bytes
9
bytes
9
bytes
9
bytes
9
bytes
9
bytes
9
bytes
9
bytes
9
bytes
9
bytes
9
bytes
15
bytes
7
bytes
1
byte
** See Custom Information section (Section 6) for custom units of measure.
Each of the first ten process values are sent in the fixed decimal format of XXXX.XXXX with leading
and trailing zeros inserted to maintain the nine character length. The next three fields are ASCII text
strings followed by the <RETURN>. Example: The nine bytes for an air in-leak of 10.0 SCFM would
be: 0010.0000, or 48,48,49,48,46,48,48,48,48 ASCII.
