There’s an old joke about how to tell how tall a building is using a barometer. The funniest answer is to find the building owner and offer them a nice barometer in exchange for the information. We wonder if [DiodeGoneWild] has heard that one since his recent video details how to measure temperatures using an ohmmeter.
The idea is that wire changes its resistance based on temperature. So if you know the resistance of a lot of wire — maybe a coil — at room temperature and you can measure the resistance at temperature, it is entirely feasible to calculate the amount of temperature that would cause this rise in resistance.
Of course, there are many ways to measure resistance, too. It’s probably possible to measure parameters like operating current and estimate temperature for at least some circuits. The wire’s material also plays a part, and the online calculator lets you choose copper, aluminum, iron, or tungsten. You also need a lot of wire, a very accurate resistance measurement, or, preferably, both.
There are many ways to accurately measure resistance, of course. Then again, you can also get resistors specifically for the job.
Resistance Temperature Detectors are a very common methof measuring temperature in industrial applications. High precision platinum sensors can give very accurate meaurements. Most common way to use them is in a Wheatstone bridge type circuit.
I look at the counterweight of the overhead wire on railroad. they go up and down on cold or warm days
There is a sidewalk installed next to the highway north of where I work. Clearly, somebody failed to properly implement the expansion joints. I’ve driven past on days in deep summer where the slabs had “tented” so far out of the ground that the sidewalk looked like a sawtooth wave. Temperature is proportional to amplitude/sin theta?
Photonic Thermometers.
https://www.nist.gov/news-events/news/2023/08/detangling-light-based-thermometers-combs
I look at an ant hill. Activity => temperature = “good”. No activity => temperature = “not good”.
Another option is to drop the barometer from the top of the building and time its descent.
Hot wire MAF (mass air flow) sensors used in fuel injected engines to measure air intake also use this principle. Wire in airflow is heated by constant voltage, and then current through it is measured. Air flowing cools the wire decreasing its resistance, and increasing current. Of course temperature compensation is needed.