It's for a dairy. There's one on each milking bail.
It has a separate sensor connected to it that the milk flows through.
When milking begins for each cow, the sensor tells the board when milk begins to flow ...
The board then switches vacuum to milk from just one teat of the udder for about 8 seconds ... and the sensor mentioned above measures conductivity to check for Mastitis.
After 8 seconds it swaps to the next quarter ... measuring each in turn.
If there is an abnormal reading, milking stops (for that cow) and an alarm signals the milker to investigate etc.
It provides a comparison between quarters ... often mastitis begins in just one quarter of the udder before it can spread to the others.
It also compares with the expected reading for the herd.
You can set the percentage difference parameters at the main controller hence the CAN bus.
Cows have RFID eartags or collars, so the system knows which cow is in each bail ... and allows the farmer to keep tabs on any problems ... animal health issues, milk yield, individualised feeding etc ... though that of course is with further equipment.