Hi,

May be, because a difficult with English, that I have, I can’t understand what you mean with “WHERE IS THE COUNT FROM“

However I can give you some general explanations:

1 – That I know, the scale electrical unit - “PLC unit” is arbitrary and depends of the vendor / product, and of many factors, like for example, the module resolution. I don’t know a standard to it (maybe only for Profibus PA instrumentation devices, which works directly with real values).

2 – For Voltage or Current measurements a S7-200 has the scale relationship: 100% of the range (for example 10V or 20 mA) corresponds to 32000 in “PLC units”.

3 – For Voltage or Current measurements a S7-300 / S7-400 has the scale relationship: 100% of the range (for example 10V or 20 mA) corresponds to 27648 in “PLC units”.

4 – For temperature measurements a S7-200, 300 or 400 have a scale relationship of 1:1, 1:10 or 1:100 (for example 36,5 Celsius corresponds to 365) in accordance of the type of the sensor.

5 – The scale relationships are decrypted in the S7-200 Manual (http://support.automation.siemens.com/WW/view/en/1109582) appendix A and S7-300 module data manual (http://support.automation.siemens.com/WW/view/en/8859629) chapter 4.