4.1
To convert PIRVOL milliampere output to % by volume
gas concentration, use the following formula:
(milliamp signal – 4.0) x 5.625 = % by volume propane
Example:
(4.0 – 4.0) x 5.625 = 0%
(12.0 – 4.0) x 5.625 = 45% by volume
(20.0 – 4.0) x 5.625 = 90% by volume.
Refer to Table 1 for a detailed description of current
outputs.
Maximum loop resistance: 580 ohms at +24 vdc. See
Figure 1 for further information.
PIRVOL-LT CROSS SENSITIVITy—
PIRVOL-LT provides a linear analog 4 to 20 mA signal
output in response to methane vapor concentration
of 0 to 90% by volume. The presence of other
hydrocarbon vapors in the sample stream will cause
an increased signal output from the PIRVOL-LT. The
tables below show the device output in response
to other hydrocarbon vapors. All device readings
are listed in % volume indicated, and all tests were
performed with a methane calibrated PIRVOL-LT.
2
95-8522
Figure 1—4 to 20 ma Current Loop Resistance
Table 1—Current Loop Output Levels
and Corresponding Status Indications
Current Level
Status
23.0 ma
100% by volume
20.0 ma
90% by volume
4.0 ma
Zero gas level (0% by volume)
2.2 ma
Zero calibration in progress
2.0 ma
Span calibration in progress
1.8 ma
Calibration complete - remove gas
1.6 ma
Calibration fault
1.0 ma
Fouled optics
0.8 ma
24 vdc line low (less than 17.5 vdc)
0.6 ma
Calibrate input active at power-up
(probable wiring fault)
0.4 ma
Active channel fault
0.2 ma
Reference channel fault
0.0 ma
CPU system fault, warmup
Ethane
% Gas
Reading
0%
0
20%
24
40%
53
60%
85
80%
115
100%
>120
Cross Sensitivity of PIRVOL-LT to Ethane
Cross Sensitivity of PIRVOL-LT to Propane
Propane
% Gas
Reading
0%
0
20%
3
40%
6
60%
9
80%
13
100%
18
Cross Sensitivity of PIRVOL-LT to Butane
Butane
% Gas
Reading
0%
0
20%
8
40%
20
60%
38
80%
66
100%
102
C1964
18
20
22
24
POWER SUPPLY VOLTAGE (VDC)
26
28
30
32
MAXIMUM LOOP RESISTANCE (OHMS)
400
500
600
700
800
900
LOOP RESISTANCE (OHMS)
