Analog Modules in siemens S7 400 PLC

[Kakka]

Hi..all..I am a newbie in this field..trying hard to acquire some good knowledge in this field.

While studying about the analog input modules in Siemens..i came across modules which have 13-bit and 16-bit resolution..

Actually where comes the difference bet this 2 modules...is it in the measuring ranges of the two modules..

I know that a 16 bit modules which i use has a measuring range of

-27648 (-100%) to 27648 (+100%) and i know that for a module having res. less than 16, the LSB will be left justified.

Now what will be the case if it is a module having 13-bit resolution...

I am looking for help from some one in this topic..

 

[RMA]

I'm not quite certain exactly what you're after here. The Siemens AI modules are standardised so that the value you see is effectively the same regardless of the resolution of the module.

The difference is the way the value changes, the "step" for one bit (LSB) difference will be larger for the 13 Bit module than for the 16 Bit module. For example you might have a value of 136.25 kg (after scaling and converting to engineering units) with your 13 Bit module. If the value at the input increased enough to raise the raw input value by 1 Bit (LSB) then your engineering unit value might increase to 136.5 kg (depending on the scaling). With a 14 Bit card under the same conditions, a lower increase of the incoming signal would be necessary to increase the raw value by 1 Bit and this would then display as 136.375 kg after scaling.

Sounds as clear as mud, I know. Basically, it's just a question of resolution, the more Bits the smaller the differences in signal level that can be detected.

 

[Kakka]

thank you..

Thank you very much for your reply. Now its some what clear for me..