Sauna thermometer types: dial, electronic and cable sensors

Sort sauna thermometers by two questions. What does the sensor react to? And where does the reading show up?

By how the sensor works

• Mechanical dial. Coiled bimetallic strips are commonly used in mechanical dial thermometers to move a pointer.¹ No power is involved. The coil is explained in the how-it-works page.
• Thermistor type. An NTC thermistor is commonly used as a temperature sensor.² It's an electrical part, so something has to read it and show the result.
• RTD type. RTDs are useful over larger temperature ranges than thermistors.²
• Thermocouple. It produces a temperature-dependent voltage. It's self-powered and needs no external form of excitation. Its main limitation is accuracy.³

A maker's page won't always say which of these is inside. When it doesn't, don't guess. Use the model's manual.

By where the reading shows

• Wall dial. Made to be watched from the bench. One maker sells a round model, 4 in across, and describes it as an in-sauna thermometer.⁴
• Combined thermo-hygrometer. One face holds a temperature scale and a humidity scale. One maker's listing is for a combined thermometer and hygrometer for a sauna, fixed into the wall paneling with 5 stainless steel screws.⁵
• Heater-control sensor on a cable. The reading isn't on the sensor at all. It goes to the heater's control unit. One maker lists a sensor for the heater control with a 4-metre cable.⁶ The difference from a wall gauge is covered in the control-sensor page.

What to compare

• Sauna or wet-area use. Look for the maker saying the gauge is meant for a sauna.
• Power. A mechanical dial has none to run out. A thermocouple is self-powered, though the display circuit it feeds may not be.³
• Cable. A cable sensor's wire sits in the heat too. One maker says its cable is permanently soldered to the sensor.⁶ Cable ratings are in the materials page.
• Mounting. One maker says installation location will greatly impact results.⁴ Read the mounting page before you drill.

A word on wiring

A sensor that connects to a hard-wired heater control means licensed electrical work. It isn't DIY. The maker of one such sensor says to always check the product's user manual for the sensor location.⁶

A plain wall dial has no wiring. It just screws to the panelling, and the maker's sheet shows how.

Wireless and app units

This site has no saved maker source covering wireless or app-connected sauna gauges, so it says nothing about their heat limits. Their own manuals are the only guide. Look for a stated temperature rating for the sensor, not just the app.