Interfacing 32V analog signal with STM32

[SSona.11]

I need a help. I want to interface 32nos of 32V Analog signals with microcontroller. i also need Ethernet connectivity. I've selected STM32F746ZGTx controller for my application. 

I want to know the industrial way for to interface these higher voltage level signals with STM32. I've also selected CD74HC4067 along with voltage divider circuitry please tell me if i am going in the right direction or not and kindly share sample of ethernet circuit and analog signal interfacing circuitry. 

[Peter BENSCH]

A simple voltage divider with resistors and some protection is actually nothing to call an industrial solution. Due to its sharper curve characteristics a TVS (transient voltage suppressor) would be better protection than a simple zener diode, in addition to that Schottky diodes from GND to ADC input & from ADC input to VDD would be highly recommended to avoid overvoltage stress at the parasitic body diodes.

However - the industrial way of interfacing these input voltages is usually an optocoupler for galvanic isolation, while the optocoupler can be controlled passively (lossy) or actively (much lower losses). By using an active interface you can also interface directly with the STM32, i.e. without optocouplers. Such an active interface could be the CLT03-2Q3 (datasheet on tab Resources), which is targeted towards 24V applications but can also work on 32V without any problems.

The so-called High side - non isolated configuration shown at the bottom of page 11 may be the circuit you can use in your application (High Side got its name from the sensor contact at the input).

Good luck!

/Peter