1-11 Hz to DC voltage signal
Thanks for the clarification.

If the sensor has a digital output with frequency proportional to flow rate, it will be a lot easier to use this directly with a microcontroller.

There is no need to convert to analog. In fact, PWM output will most likely be more accurate and noise-proof.

The typical topology would be:


Several CAN-enabled microcontrollers
Each acquires data from several sensors and transmits on CAN bus


So, you have a compromise to make with the price of the microcontroller modules versus the price of cables, ease of installation, etc. If you have, say, 10 sensors in close proximity, then it makes sense to wire them all to the same micro, and then wire that to CAN bus. And if you have another group of sensors some distance away, then compare the price of an extra micro with the extra cables and installation labor.

There are several cheap micros with CAN built-in. Check LPC11C14, for example.