AM-TFS Thermal Flow Switch

A thermal flow switch answers one question: is the flow above or below the point I set. Two resistors sit in a sealed probe, one heats and one references; when the flow carries the heat away faster than the setpoint allows, the contact changes. There is no rotor to jam, no paddle to bend and nothing to calibrate beyond turning the potentiometer.

That indifference is what sells it — pneumatic and hydraulic lines, cooling water, cutting fluid, lubricating oil, and pump protection where the flow is either there or it is not. What it cannot do is tell you how much: the datasheet gives velocity ranges (1–150 cm/s in water, 3–300 in oil, 20–2000 in air) and a repeatable contact, not a measurement.