Thanks guys I will return the Hikvision and get this. I could hear the thing clicking across the room 20 feet away!
Basically from what I understand the thermal sensor's own heat and environmental changes can affect the sensor so to maintain accuracy a mechanical shutter needs to periodically...
How bad is the thermal calibration clicking? I am testing out the Hikvision DS-2TD1228-3 and its pretty bad. Very loud and constant, every 2-3 minutes, even after the sensor is warmed up.
