An external power supply is required. The 4 to 20 mA output
version of the Ultima Gas Monitor requires 7 to 30 VDC at the
sensor input for proper operation (10 VDC required for
Combustible IR models). All connections should be made by
following appropriate wire code procedures. For direct mA output
modules, ensure minimum and maximum power requirements are
met.
• See TABLES 1-4 through 1-7 for typical cable length and wire
size for installation.
"
WARNING
When using any of the the Ultima accessories (such as the
Auto-Calibration Module or Relay Module) with the 4 to 20
mA output Ultima Gas Monitor, the three-wire unit must be
used. Failure to use a three-wire unit will damage the
electronics within the Ultima Gas Monitor which can result
in serious personal injury or death.
When installing in a hazardous area, be sure to install your
Ultima Gas Monitor according to National Electrical and local
procedural codes. Failure to do so can result in an unsafe
condition.
Table 1-4. Cable Length and Wire Size (Toxic Gas or Oxygen) Sensor,
4-20 mA Signal Output (Two Wire Sensor)
In all installations twisted-pair, instrument quality cable is required.
In applications where interferences from RFI or EMI or other noise sources exist,
shielded cable is recommended.
WIRE
SIZE
MAXIMUM CABLE
LENGTH IN FEET
@ 24 VDC
MAXIMUM
LOAD
RESISTANCE
MAXIMUM CABLE
LENGTH IN FEET
@ 12 VDC
MAXIMUM LOAD
RESISTANCE
22 AWG 7,000 600 Ohms 4,000 100 Ohms
Table 1-5. Cable Length and Wire Size Combustible Gas Sensor,
4-20 mA Signal Output (Three Wire Sensor)
In all installations twisted, three-conductor, instrument quality cable is required.
In applications where interferences from RFI or EMI or other noise sources exist,
shielded cable is recommended.
WIRE
SIZE
MAXIMUM CABLE
LENGTH IN FEET
@ 24 VDC
MAXIMUM
LOAD
RESISTANCE
MAXIMUM CABLE
LENGTH IN FEET
@ 12 VDC
MAXIMUM
LOAD
RESISTANCE
22 AWG 1,000
600 Ohms
---
250 Ohms
18 AWG 2,500 900
16 AWG 4,200 1,400
12 AWG 10,000 3,600
Chapter 1, Set-up
1-14
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