analog input to logo plc

[dutchy1]

Is anyone familiar with siemens logo plc.I need to interface to a varying analog signal and convert this voltage to a reading in degrees. From the application examples it says the logo cannot store analog values directly so use a counter and compare the analog value to this. I have an idea which blocks to use for the fbd (function block diagram )
1. Analog input
2.Analog amplifier
3. Analog comparator

I was thinking of using an off delay timer to hold the value so it will be sampled correctly by the plc.

Can anyone offer some assistance.
I havent done plc programmig before.

 

[Skogsgurra]

Hello,

Yes. I worked "intimately" with the LOGO! (the "!" is part of the name) last fall. My task was to see why there were some discrepancies in the analogue inputs between different units. After sorting out the batch that didn't quite "behave", I found the performance a lot better than I had expected. Offset, linearity and scale factor combined was never more than .3 percent of FS and around .2 in most individuals. That's pretty good for a USD 100 device.

The version I worked with (last fall) did not have an analogue amplifier available. But it can scale the analogue input (I7 and I8) so that the display reads in degrees C or F or whatever you need.

I am not quite sure what your question is. Are you trying to circumvent the lack of analogue computing blocks by using a counter and comparator to find out what the analogue value is? That would be possible, as far as I remember.

Gunnar Englund

http://www.gke.org

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