Rockwell Automation 61C345 4 Input 4-20mA Analog Rail Module - Manual (Page 36)

5Ć4
Step 1. Verify that the application program(s) is correct. Check to
see that the program is referencing the correct registers
(AutoMate) or symbolic names (DCS 5000/AutoMax). In
DCS 5000/AutoMax applications, make certain that the
program is not attempting to write to the input channels.
Step 2. Stop any application tasks that are running. Turn off
power to the Analog Rail module.
Step 3. Try to clear the condition by disconnecting and then
reconnecting the I/O Rail cable. Make certain the
connections are tight. If applicable, check the
connections between the host and the Local I/O Head,
the AutoMate Remote I/O Head, or the DCS 5000/AutoMax
Remote I/O Head. Check that the pins on the input
connector are not bent.
Step 4. Turn off power to the external hardware. Verify that the
wiring to the external hardware is tight and functioning
correctly.
Step 5. Turn on power to the external hardware.
For input channels, use the Executive software to read
the value on the input channels. Use an ammeter to read
the input signal and compare the two. If the signal is
being converted correctly, there is aproblem with the
external hardware or wiring.
Step 6. Troubleshoot the external hardware, the wiring, and the
host.
5.4 Constant UnderĆRange
Problem: the underĆrange bit (12 decimal) on an input channel
register is constantly set to 1. Assuming that the power supply for
the external hardware connected to the input channel is providing
an input signal within the specified limits (4Ć20mA), the possible
causes of this problem are a loose connector on the analog input
section of the faceplate, loose or malfunctioning wiring, incorrect
(reversed) input signal wiring on the module faceplate, or a blown
input channel fuse (32mA fuse). Follow the steps below to isolate
the problem.
Step 1.
Stop any application tasks that are running. Turn off
power to the external hardware connected to the module.
Turn off input power (120 VAC or 24 VDC) to the module.
Step 2. Verify that the 12Ćpoint connector on the analog section of
the module faceplate is securely attached to its mating
half.
Step 3. Verify that the signal wiring on the module faceplate is
correct. See step 9 in section 3.2 for more information.
Verify that the wiring is tight and functioning properly.
Step 4. Turn on power to the module and to the external
hardware. Use the Executive software to read the value
on the input channel. Use an ammeter to read the input
signals at the terminal point and compare the two. If both
read zero, verify that the external hardware is operating
correctly. If the external hardware is operating correctly,
the 32mA fuse for the input channel may be blown.