Oldham OLCT 200 User Manual page 20

2.6.3 3-Wire 4-20mA Mode Installation
CAUTION: OLCT 200's equipped with the 10-0233 I/O Power Supply board only
operate as 3 or 4-wire 4-20mA transmitters and are not compatible with 2-wire
intrinsically safe installations (see sections 2.6.1 and 2.6.2). Such units should not be
combined with 10-0247IS Sensor Heads without flame arrestors unless the area is
classified as non-hazardous.
OLCT 200's equipped with the 10-0233 I/O Power Supply and 10-0234 Alarms /
Modbus option are NRTL certified as suitable for Div 1 & 2 Groups B,C,D explosion
proof installations with the 10-0247 or with any sensor head with an equivalent CSA
certification.
Description:
3-wire sourcing transmitters require an additional dedicated 24 VDC wire. The 4-20mA
loop current is then delivered, or sourced, from the transmitter output and the receiver
device must not provide 24 VDC from its input terminal. When the OLCT 200 is
equipped with the bottom 10-0233 I/O Power Supply board shown in Figure 2-5, the 2-
wire 4-20mA output is disabled and one of the 10-0233's 3-wire outputs must be used.
TB2 terminal 2 is for ECHEM toxic / oxygen 3-wire 4-20mA output signals and TB2
terminal 3 is for LEL 3-wire 4-20mA output signals.
Instructions:
Unscrew the cover on the OLCT 200 explosion-proof enclosure. Loosen the 2
thumbscrews holding the display assembly in place and remove it. A small ribbon
cable is attached with sufficient length to allow access to the I/O PCB mounted in the
bottom of the enclosure (Figure 2-5). Power and signal connections are to TB2 where
24 VDC, Signal and Common wires must be connected. A blocking diode protects the
OLCT 200 if polarity of the power supply is reversed but it will not operate.
Reassemble the OLCT 200. Follow the procedures and recommendations in the
receiver and power supply manuals to complete the installation. Be sure the OLCT
200 enclosure and conduit are properly grounded. Apply power and the OLCT 200
should function. Proceed to section-3.
OLCT 200 User Manual | 20