How to vary the voltage output depending on the changes in temperature?

Question

I am working with the Siemens Logo8! PLC (0BA8 version) and the purpose of my circuit seems to be simple:

If temp > 25°C then output voltage = 8V

If temp < 25°C and >15°C then output voltage = 5V

If temp <15°C then output voltage = 2V

Is there a possible way in a circuit of doing this?

I achieved a similar concept by using one Analog Input, then 2 Analog Threshold Triggers connected to a latching relay and eventually to a Digital Output. (Picture attached) However, the limitations of that system is that Voltage can be either 1 or 0.

The concept behind the circuit seems to be simple but I am really struggling to make it work and any hints will be much appreciated.

analog circuit design plc siemens voltage

Tony Stewart EE75 · Answer

simulate this circuit &ndash; Schematic created using CircuitLab
I'll send invoice on schematic entry cost ;)
and if you don't understand my schematic , try this one which I had no trouble understanding in university undergrad in my day..

How to vary the voltage output depending on the changes in temperature?

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