Fig 3. GDS-IR / LPI FIELD WIRING
Apply power to the GDS-IR / LPI and allow the
instrument to stabilize for at least one (1) hour.
IMPORTANT - Ensure there is no combustible
gas present during the auto-zero procedure.
Apply a flow of nitrogen or known ‘zero air’ if
necessary. Setting zero with background target
gas will cause erroneous readings.
Using a magnetic wand, activate the auto-zero switch
located behind the RED conduit end-cap on the Loop
Powered Display enclosure. Hold the wand in place
for at least 10 seconds, but not more than 20
seconds. The GDS-IR should momentarily output
2.2mA to indicate a successful auto-zero. The LPI
numeric display may dim or disappear momentarily.
Adjust the ZERO setting on the LPI until the display
reads “00.0”.
Apply a 0.5 to 1.0 LPM flow of 50% LEL methane
calibration gas to the GDS-IR via the 1/4” inlet
located on the bottom of the instrument. When
stabilized, adjust the SPAN setting on the LPI to read
“50.0”.
Remove the calibration gas and recheck for zero.
The instrument is now ready for operation.
INITIAL STARTUP & AUTO ZERO
During normal operation*, the output of the GDS-IR
current loop continuously indicates the concentration
of combustible hydrocarbon gas present in the
ambient atmosphere. In the event of instrument
malfunctions or calibration activities, the output
current value can be used to determine status as
shown:
OPERATION
TB1
1
2
3
4
5
6
GDS-IR
LPI
+18-32VDC
COMMON
4-20mA OUT
+
-
Red
Black
Blue
White
Auto Zero
0.0mA
Instrument Fault
2.2mA
Unit Zeroing
0.2mA
Ref Channel Fault 4.0mA
Zero Gas
0.4mA
Analytic Ch Fault
5.6mA
10% LEL*
0.8mA
Unit Warm-Up
8.0mA
25% LEL*
1.0mA
Optics Fault
12mA
50% LEL*
1.2mA
Zero Drift Fault
16mA
75% LEL*
1.6mA
Calibration Fault
20mA
100% LEL*
2.0mA
Unit Spanning
20 - 23mA Over-range
CLEANING
To inspect or clean the optics path, unscrew the
barrel of the GDS-IR. Remove the slotted setscrew
and hydroscopic filter. Loosen the small hex
setscrew on the center assembly and remove the
assembly by rotating the long barrel CW and the top
fitting CCW. Clean the upper and lower optics
windows using lint-free cloth. Reassemble in
reverse order.
After cleaning, always perform the auto-zero
operation as described above.
Note:
The Loop Powered
Indicator will NOT operate
unless the 4-20mA current
loop output (TB1-5) is
connected to COMMON at the
receiving instrument input
