
GASMAX CX Operation & Maintenance Manual, Revision 1.0
Page 11
CONNECTING
DC
POWER
&
OUTPUT
SIGNAL
WIRING
To
access
the
GASMAX
signal
and
power
connections,
remove
the
cover
on
the
GASMAX
CX
explosion
‐
proof
enclosure,
loosen
the
2
thumbscrews
holding
the
display
assembly
and
remove
it.
The
display
will
remain
connected
to
the
IO/Power
Supply
PCB
mounted
in
the
back
of
the
enclosure
by
a
short
ribbon
cable.
Route
the
power
and
signal
wires
through
the
conduit
entry
and
connect
to
terminal
block
“TB1”.
Plus
24VDC
connects
to
TB1
‐
1.
DC
Ground
connects
to
TB1
‐
4.
Channel
One
4
‐
20mA
output
is
available
on
TB1
‐
2
and
Channel
Two
4
‐
20mA
output
is
available
on
TB1
‐
3.
GDS
Corp
always
recommends
using
shielded
wire
for
signal
and
power
cable.
Figure 4-1: GASMAX CX I/O Power & Signal Wiring
CO
M
42
0
OU
T
2
42
0
OU
T
1
PW
R
R/
P
W
R
C/
4
20
IN
1
A/
C
O
M
42
0
IN
2
CH
1
CH
2
E
‐
NE
T
LOCAL
SENSOR
TO DISPLAY
TB1
–
1:
+12
‐
30VDC
Input
TB1
–
2:
Channel
1
4
‐
20mA
Out
TB1
–
3:
Channel
2
4
‐
20mA
Out
TB1
–
4:
Power
/
Signal
Common
NOTE:
THE
MAXIMUM
DISTANCE
4
‐
20
MA
SIGNALS
CAN
TRAVEL
IS
DEPENDENT
UPON
CABLE
GAUGE,
DC
POWER
SUPPLY
VOLTAGE
LEVEL
AND
INPUT
IMPEDANCE
OF
THE
RECEIVING
DEVICE.
ASSUMING
A
NOMINAL
24
VDC
POWER
SUPPLY,
100
OHM
LOAD
AND
MAXIMUM
TOTAL
LOOP
RESISTANCE
OF
750
OHMS:
#18GA,
0.0064
OHM/FT
=>
9.6
MILES
/
15.5
KM
#24GA,
0.026
OHMS/FT
=>
2.3
MILES
/
3.7
KM