What is the FAD box and do I need one?

FAQ - PS1

1. What is the diameter of the OTT pressure sensor?
2. Q: What is the FAD box and do I need one? A: The OTT PS 1 pressure probe is connected to the FAD 4 P humidity absorber by a flexible, longitudinally stable cable that contains a pressure compensating capillary tube for the atmospheric pressure. This serves as a connecting point for signals going on further, for connection to external data loggers.
   
   
3. How is the instrument configured?
4. What sorts of outputs are available?
5. Does the OPS measure level or pressure?
6. What level ranges are offered?