Dwyer GFT2 User Manual
Page 20
APPENDIX B
Internal K-Factors Table
APPENDIX C
GFT2 ASCII Commands Set
RS-232/RS-485
The standard GFT2 comes with an RS-232 interface. The protocol described below
allows communication with the unit using either a custom software program or a
“dumb” terminal. All values are set as printable ASCII characters. For RS-232
interface, the start character and two characters of address have to be omitted. For
the RS-485 interface, the start character is always ‘!’, and two characters of
address follow. The command string is terminated with a carriage return (line feeds
are automatically stripped out by the GFT2):
RS-485
!
Example: !12,F
RS-232
Cmd,Arg1,Arg2,Arg3,Arg4
Example: F
Where:
!
Start character **
Addr
RS-485 device address in the ASCII
representation of hexadecimal (00 through FF
are valid). **
Cmd
The one or two character command from the
table below.
Arg1 to Arg4
The command arguments from the table below.
Multiple arguments are comma delimited.
CR
Carriage return character
**Default address for all units is set to 11 hex. Do not submit start character
and device address for RS-232 option.
Several examples of commands follow. All assume that the GFT2 has been
configured for address 18 (12 hex) on the RS-485 bus:
1. To get a flow reading:
!12,F
The device will reply:
!12,50.0
(Assuming the flow is at 50.0% FS)
2. To get current Flow Alarm status:
!12,A,S
The device will reply:
!12,AS:N
(Assuming no alarm conditions)
3. To get Totalizer#1 reading:
!12,T,1,R
The device will reply:
!12,T1R:93.5
(Assuming the Totalizer#1 reading
is 93.5)
4. Set the flow high and low alarm limit to 90% and 10% of full-scale flow rate:
!12,A,C,90.0,10.0
The device will reply:
!12,AC:90.0,10.0
Index
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
Actual Gas
Argon Ar
Arsine AsH3
Boron Triflouride BF3
Bromine Br2
Acetylene D2H2
Cyanogen C2N2
Methane CH4
Chlorine Cl
2
Carbon Dioxide CO
2
Carbonyl Fluoride CoF
2
Carbonyl Sulfide COS
Carbon Disulfide CS
2
Fluorine F2
Hydrogen H
2
Helium He
Nitrous Oxide
Ammonia NH3
Neon NE
Nitric Oxide O2
Sulfur Dioxide SO2
Xenon Xe
K Factor
Relative to N
2
1.4573
0.6735
0.5082
0.8083
0.5829
0.61
0.7175
0.86
0.7382
0.5428
0.6606
0.6026
0.9784
1.0106
1.454
0.7128
0.731
1.46
0.99
0.9926
0.69
1.44
Cp
[Cal/g]
0.1244
0.1167
0.1778
0.0539
0.4036
0.2613
0.5328
0.114
0.2016
0.171
0.1651
0.1428
0.1873
3.419
1.241
0.2088
0.492
0.246
0.2328
0.2193
0.1488
0.0378
Density
[g/L]
1.782
3.478
2.025
7.13
1.162
3.322
0.715
3.163
1.964
2.945
2.68
3.397
1.695
0.0899
0.1786
1.964
0.76
0.9
1.339
1.427
2.858
5.858