Bulb and Capillary style thermostats use expanding liquid to open or close contacts in response to temperature changes. No matter which style or model you choose, all of the capillary thermostats operate using the same physics. A fluid is encapsulated in a metal tube (bulb and capillary) and when the temperature changes the fluid either expands or contracts. This fluid change moves the head which triggers a snap action switch either opening or closing the circuit.
The bulb is typically a larger diameter tube mounted in the material flow being sampled. The capillary is a small tube that carries the fluid away from the bulb to the head. The head can be a diaphragm or bellow, which moves with the changing temperatures.
Our capillary thermostats also offer the option of being ambient compensated to offset the differential in temperature which keeps our thermostat controls more accurate as it’s environment changes.