Omega TX91 manual Troubleshooting Guide

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5Troubleshooting Guide

a)Measure the total resistance of each device (excluding the transmitter and power supply) in the 20 mA loop, including the resistance of the lead wires.

b)Calculate the maximum allowable loop resistance using the formula:

Loop Resistance (maximum) = Vsupply -11V

0.020A

For example, a 24V power supply would give a maximum loop resistance of: 13V/0.020A = 650 ohms.

c)Make sure the power supply is rated for at least 28 mA times the number of TX91 transmitters being powered. For example, if the

supply is powering 5 transmitters, the supply should be rated for

25at least 140 mA.

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Contents User’sGuide Servicing North America Return Requests / Inquiries Introduction Calibration Instructions Introduction General DescriptionIntroduction TX91 Thermocouple Transmitter Introduction Introduction Straight line Approximation of Curve Features Models AvailableTX91 Models Available Model Number Description Unpacking Installation Mounting the TX91Assembly of the TX91 Transmitter Inside RT Mounting Track in inches TX90-BR Mounting Bracket in inches Mounting Track RT Bracket TX90-BR Wiring the TX91 Refer to Figure Wiring Diagram for the TX91 Potentiometers Calibration Instructions Equipment RequiredSet-up of Equipment Calibration Procedures Refer to Figure Calibration Instructions Calibration Set-Up Calibration Set-Up. Alternate Calibration Values for the TX92 Troubleshooting Guide Current rating on the power supplyTroubleshooting Guide Accessories Model No DescriptionSpecifications GeneralInput Intrinsically Safe Interconnection Diagram WARRANTY/DISCLAIMER Shop online at omega.com