Bench TOP Configuration, Power Supply | Emerson 00825-0100-4075

Quick Installation Guide

Smart Wireless THUM Adapter

00825-0100-4075, Rev BA February 2010

Power Supply

Minimum loop load of 250 Ohms.

The THUM Adapter communicates via and derives power from a standard 4-20 mA/HART® loop. The THUM Adapter causes a small voltage drop on the loop which is linear from 2.25 V at 3.5 mA to 1.2 V at 25 mA. Under fault conditions, the maximum voltage drop is 2.5 V.

The THUM Adapter will not affect the 4-20 mA signal under normal or fault conditions as long as the loop has at least a 2.5 V margin at the maximum loop current (25 mA for a typical 4-20 mA/HART device).

Limit the power supply to 0.5 Amps maximum, and voltage to 55 Volts DC.


Loop Current	THUM Adapter voltage drop
3.5 mA	2.25 V
25 mA	1.2 V

Load Resistor

If required, add a load resistor as shown in Figure 8, 12, and 16. The resistor should be adequately rated for the application (1W minimum) and be compatible with the supplied splice connector which accepts wire sizes from 14 to 22 AWG.

BENCH TOP CONFIGURATION

When performing bench top configuration it is suggested that you connect the THUM Adapter to a wired device. If this is not possible the following wiring diagrams can be used. For bench top configuration ensure that the power supply that you are using is limited to 0.5 Amps maximum.

Figure 2. THUM Adapter Only, Powered by a Current Source (Such as a Fluke 744)

THUM Adapter

	Green	Ground
	Red	Ground
	Red	+
	Black	20 mA
	Black	Current
		Current
	White	- Source
	Yellow
		HART
		Modem