While the device is about the size and shape of a shield for an Arduino it clearly isn't one and has nothing to do with Arduino. It appears to be part of the controls for a refrigeration system.
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It is certainly at least Arduino compatible because it is mounted on Arduino Mega (it is not visible in the picture but if you have doubts - i can make a picture of a back side of device).
And what makes you doubt that it could work with 3 sensors? In a scheme attached (pdf) you can see three sensors plugged ???