OLCT 700/710 TP
Page 10 of 45 Rev. C.1 OLCT 700/710 TP Instruction Manual
2.7 Field Wiring
Oldham OLCT 700/710 TP solid-state H
2
S detector assemblies require three conductor connections
between power supplies and host electronic controller’s 4-20mA output, and 2 conductor connections for
the Modbus™ RS-485 serial interface. Wiring designations are + (24 VDC), – (0 V), mA (detector signal),
and Modbus™ RS-485 A (+), and B (-). Maximum wire length between detector and 24VDC source is
shown in the Table below. Maximum wire size for termination in the Oldham J-Box accessory is 14 gauge.
Max loop load resistance between green and black wire (analog signal output) is 500 ohms. Minimum loop
load resistance between green and black wire is 100 ohms. This is considers wire diameter, wire length,
max operating temperature and selected termination resistor.
Table 2: Wire Gauge vs. Distance
NOTE 2: Shielded cable is required for installations where cable trays or conduit runs include
high voltage lines or other possible sources of induced interference. Separate conduit or tray
runs are highly recommended in these cases.
NOTE : It is essential that the instructions provided by the manufacturer of the cable gland are
followed and the braid is correctly connected.
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