These units are able to display water temperature and air temperature.
The water temperature is taken from a sensor located in the transducer.
The air temperature is measured by a silver thermistor located at the end of the cord connected to the gauge.
The temperature is measured from wherever this bulb is located.
It can be left in the dash or routed to somewhere you want to read.
If you have a cabin and want the outside air temp you would route the bulb to the outside air.
The sensor can be secured a number of ways; cable clamps, drop of silicone, tie wraps are all good.
As long as the silver part of the sensor is open and free of coverings