User's Manual

5
WARNING: Qualified personnel should perform the installation according to applicable
electrical codes, regulations and safety standards. Insure correct cabling and sealing fitting
practices are implemented. Also, never install the sensor pointing upwards.
2.5 System Design Specifications
Supply Voltage:
10 to 30 VDC
Power Consumption:
• Toxic Sensors (2-wire 4-20mA operation): 25 mA @ nominal 24 VDC.
Memory:
Non-volatile E2 memory retains configuration values in the event of power outages. Loop
Resistance at nominal 24 VDC power: 650 ohms maximum in 2-wire mode.
2.6 Field Wiring Installation
4-20mA Transmission Range Info:
The distance 4-20 mA signals can travel is dependent upon several factors including the cable
gauge, DC power supply voltage level and impedance of the input of the receiving device.
Assuming a nominal 24 VDC power supply, the maximum total loop resistance should be 650
ohms. See Appendix B for resistance table.
2.7 2-Wire 4-20mA Explosion Proof Installations
ECO-A-X equipped with smart sensor heads are NRTL (Nationally Recognized Testing Lab)
certified as suitable for explosion proof installations. All ECO-A-X’s are NRTL certified for
explosion proof installations as long as the sensor head is certified as explosion proof.
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 ECO-
A-X Display assembly shown in Figure 2-3 consumes <2.5 mA of quiescent current. Toxic
electrochemical sensors generate their own signals and therefore require no additional current.
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 ECO-A-X 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 ECO-A-X 2-wire 4-20mA output automatically correct for polarity so positive and negative
are interchangeable. Reassemble the ECO-A-X. Follow the procedures and recommendations
in the receiver manual to complete the installation. Be sure the ECO-A-X enclosure and conduit
are properly grounded. Apply loop power by appropriately powering the receiver device (DCS,
PLC, Controller, etc) and the ECO-A-X should function.