I am doing a presentation on Modbus RTU communication and I am wondering how does value that sensor reads gets converted to binary form?
I read it that sensor has ADC which converts analog value such as temperature to digital and then that digital is being read by master after it sends request.
Is this true? Do sensors really have ADC in them? And if now how does it really work then?
Conforming to Modbus RTU protocol is the responsibility of whatever is hooked to the physical Modbus medium (RS-485, etc.) in use. Is that the 'sensor'? Then it obviously has an ADC in it, as well as some other stuff in addition to the physical sensor. But I could just as easily hook a raw thermistor or thermocouple (no internal electronics at all) sensor to some Modbus interface component, and it would thus need an internal ADC in order to do its job.
What does not work is to try to connect a thermistor or thermocouple sensor directly to the Modbus medium. You need an ADC and a protocol formatter too, somewhere.
