Hardwiring an auto-off feature into a measurement tool or instrument, like a digital thermometer, is dumb and bad. Don’t do it. Providing it as an option is probably useful in a lot of cases, but turning a tool off after an arbitrarily chosen length of time is dumb and bad.
I recently wanted to gauge how hot a couple of DJI Action 2 cameras became during charging. I have some digital thermometers that accept thermocouple temperature probes and one of them has outlets for four thermocouple probes and possesses a “MAX” button which tells the device to keep an eye out for and display the highest temperature sensed during a given use period.
I used some teflon tape (the same Nitto NITOFLON 903UL tape mentioned in a previous post: Trying to heat-test some Nitto and Chukoh PTFE adhesive tapes) to attach a “hot junction” (the exposed metallic tip of the thermocouple) to the case of each of the two cams. The thermocouples were quite sproingy, so I used some clear silicone rubber bands for strain relief to prevent the thermocouple tips from lifting off.
When I returned to this setup after an indeterminate interval of time (less than an hour but more than fifteen minutes), I found the thermometer switched off, its screen dark. I hadn’t been videoing up to that point, so those readings are lost to posterity, but I turned it back on, set up a camera, aimed it at the instrument’s screen, and recorded the video from which the clip above is taken.
The highest temperature attained in the clip is 45.9°C. However, I have measured though not yet documented via photo/video, temps a few degrees above 50°C. To put these numbers in a bit of perspective, Kohler (the bathroom fixtures company) says that comfortable bathwater ranges from 32 to 40° C. These devices can get a bit uncomfortable to hold and DJI responded to customer unease regarding their toastiness when recording at high resolution and high framerate by whipping up some plastic cases that don’t do anything to cool the cameras but do insulate your fingertips from the cameras’ metal shells. I haven’t used the cases yet.
The less-featureful, single-thermocouple digital thermometer shown in this photo (a Lutron TM-902C, reviewed by electronupdate here: TM-902C K-TYPE THERMOCOUPLE AND THERMOMETER REVIEW AND TEARDOWN) will run for as long as its battery holds up, but it’s missing maximum-temperature recording functionality.