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4.6.1 2-Wire 4-20mA Mode Installation
Description:
The 2-wire current sinking transmitter is the easiest and most economical to install since there
are only two wires. All of the power needed comes from the current loop and wire sizes may be
smaller. However, only very low power applications are eligible for such transmitters. The
AMC-DTR Display assembly shown in Figure 5 consumes <2.5 mA of quiescent current. Toxic
and oxygen electrochemical sensors generate their own signals and therefore require no
additional current. If a 4-20mA output is all that is required for toxic / oxygen measurements (no
LCD backlight, alarms or RS-485) the AMC-DTR may be used in the 2-wire mode.
CAUTION:
It is important to understand the receiver, or controller device must supply the loop power in 2-
wire 4-20mA modes. Be sure the receiver to be used supports this type of operation.
Instructions:
Unscrew the cover on the AMC-DTR explosion-proof enclosure. Loosen the 2 thumbscrews
holding the display assembly in place and remove it. A small sensor cable is attached with
sufficient length to allow access to the back of the display assembly where 2 position TB1 is
located. Route the receiver wires through the conduit entry and connect to TB1. Steering
diodes in the AMC-DTR 2-wire 4-20mA output automatically correct for polarity so positive and
negative are interchangeable.
recommendations in the receiver manual to complete the installation. Be sure the AMC-DTR
enclosure and conduit are properly grounded. Apply loop power by appropriately powering the
receiver device (DCS, PLC, Controller, etc) and the AMC-DTR should function. Proceed to
section 5.
Figure 5: DTR-10-0232 Display / 2-Wire 4-20mA Assembly
AMC-DTR Sensor Transmitter User Manual
Reassemble the AMC-DTR.
Follow the procedures and
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