hi Eliannya,

I don´t know what you are doing, but the analog input representation that you show with your graphs are not matching the values as they should be according the manual:

Measurement ranges of the analog inputs for voltage and current (SB and SM)

obviously you are measuring the 0..5V on the module with a range of 0-10V, right?

Try to use the measuring range of 0..5V or +/- 5V.

Also use the rigth datatype on the input word. they should be integer, not unsigned integer or word.

the jump from 65535 to zero is on the edge of a word. 16 bits can only represent values from 0 to 65535. But without further information I can´t say what is going wrong here.

Please share information about the parameters of the module and how you process ist values.

hope this helps,

regards,

If you actively measure the signal and use the s7-1200 Trace function on these analog inputs, do you see the value drop to 0 and hold at 0 as long as the meter is measuring, and start rising as soon as the meter is removed?

I've seen this many times where some device builds up a static charge (like on rotating equipment which have no static removing "fingers" added).

Sometimes the analog module is not properly bonded (ground not terminated).

Sometimes the analog input is wired without galvanic isolation and adjacent analog inputs have "relative" rather than absolute AI- signals, meaning the AI+ to AI- is a differential input rather than an absolute voltage at AI+ and 0V or common bonded with AI-.

If you temporarily jumper all the AI- to ground, do your analog inputs start working?

OH, YEAH, are your spare AI's all jumpered?  If not, you can (will) get drift of adjacent AI channels.  It's in the manual for the modules - when configured for voltage.  In Current inputs, no jumpers.

Eliannya

I have my 6ES7 231-4HD32-0XB0 (SM 1231 AI4) Analog Input Module for my project. It receives 0 to 5 VDC as voltage input and I have a problem with my analog inputs

Here is the graph of my analog inputs (IW64 & IW66) built into the CPU. For months of using the PLC, all of the analog inputs in analog modules are working like this. Upon supply of 5VDC, PLC will have 13000 to 14000 decimal values. See graph 1

After modification in the program, we encounter irregularities in analog inputs on analog modules. Upon supply of 0 to 1 VDC, the decimal value in PLC will spike up to 65000 decimals. Then as you can see on graph, upon supply of 2.3 VDC, the decimal value in PLC will drop to 0 decimal. See graph 2

I tried to check the settings for the analog module but I don’t see any relevant parameter that can affect the analog inputs. I also tried resetting the PLC to factory default, but still didn’t work. I also isolate the electrical wiring of the PLC but still didn’t work. I check the analog input from the sensor but it gives the voltage correctly upon testing on the multimeter. We also tried other sensors but the same result.
I would like to know the possible reason for the analog input irregularities. Is it in the parameters? Wiring? I hope you can help me with this. Thank you in advance.