S7-1500 AI module 6ES7531-7QD00-0AB0 unused channels

Hello! I'm having some problems with finding information about unused channels for the S7-1500 6ES7531-7QD00-0AB0 AI module.

The only information in the manual is "Deactivate the input if it is not going to be used. The module cycle time is shortened and the
interference factors that lead to failure of the module (for example, triggering a hardware
interrupt) are avoided."

I've found information on support industry Siemens site about the SM 1234 analog input/output module that "Unused voltage channels should be shorted."

This method applies to the S7-1500 6ES7531-7QD00-0AB0 AI module as well?

Hi,

basically the answer is simple. If you have the manual for your S7-1500 module (product number) and in this manual is only stated to deactivate the unused channels, thats it. Why should statements form another manual for another module also apply to your used manual?

regards

sancruz

Thank you for your answer!

I wanted to be sure, cause I've met this requirement for older S-300 and S-1200 modules.

The reason for shorting unused AI channels is to help the multiplexed AI modules get more accurate information.  As it switches from AI channel to AI channel, it has to pause to let everything stabilize before taking a reading on the AI channel.

With unused channels, they start to generate a natural "DC float" voltage that disrupts the multiplexor circuits.

When unused channels are jumped/shorted, there is no DC float and the multiplexor works very well.

For more powerful AI modules (s7-1500's in particular) where each AI has its on A/D circuitry and are not multiplexed, there is no need to short the unused channel.

However, for simplified diagnostics configuration, it is better to disable unused channels entirely.

Also, not all AI modules/channels are able to be disabled.  In those cases, you absolutely should jump/short unused VOLTAGE input channels.

And for the record, if unused AI channels are configured for current input, do not jump/short them.  If you feel must do something, instead you can do this: install a 500Ω resistor across the input terminals.  Note: I never do this and have not had any problems.

ionut.dobrin

Thank you for your answer!

I wanted to be sure, cause I've met this requirement for older S-300 and S-1200 modules.