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
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.
