Mitsubishi Electronics MELSEC-F Manuel D’Utilisation

8 Troubleshooting

FX

3G

/FX

3U

/FX

3UC

 PLC User's Manual - Analog Control Edition

FX

3U

-4AD/FX

3UC

-4AD (4-channel Analog Input)

This chapter describes troubleshooting methods and error codes.
If the A/D conversion data is not input, or if the proper digital value is not input, check the following items:
• PLC version number
• Wiring
• Program
• Error status

Verify that the PLC being used is of the following version or later.

→ For a detailed description of version number check method, refer to Section 1.3.

Check the wiring as follows:

The 4AD needs driving power. Verify that the power supply line is properly connected. Also check that the 24
V indicator lamp of the 4AD is on.

Use the 2-core twisted shielded cable for the analog input line. In addition, be sure to separate the analog 
input line from any other power lines or inductive lines.

To use the current input mode for a channel, be sure to short-circuit the line between the V+ terminal and the 
I+ terminal of the channel.
Without short circuiting the terminals, it is impossible to obtain the correctly converted digital values.

→ For a detailed description of wiring, refer to Chapter 4.

Check the program as follows:

Check whether the device holding digital values contains any values written by other programs.

Check if the averaging time or the digital filter function is set for the same channel. It is not possible to set both
functions for the same channel.

FX

3U

 Series PLC

Ver. 2.20 or later

FX

3UC

 Series PLC

Ver. 1.30 or later

FX

3G

 Series PLC

Ver. 1.00 or later

FX

3UC

 Series PLC

Ver. 1.30 or later