What kind of thermometer should I get for reliable readings? (testing a fridge) - Page 1
Forum section: electronics / testgear

author: Freesurfer
author_rank: Regular Contributor
timestamp: July 30, 2023, 10:24:29 am
content: I have a refrigerator and I am not sure if it is performing correctly. I also have some junk peltier mini coolers and such that would be interesting to try. So the solution is simple, grab whatever thermometer I have and stick it in there to take some readings.But oh, not so fast.. I have little faith in the various cheap window thermometers, weather stations and such. If you let them sit indoors in the same room overnight, the indoor and outdoor temperature readings are normally off by anywhere between 1-3 degrees. I put a weather station inside my fridge, which reads 9C, which is way higher than my suspicions are. Even if it may be correct, I have little trust in the device.So I wonder what options I have and what kind of thermometer I am looking for to get trustworthy readings. On the other hand I am not looking for some "industrial grade calibrated equipment". Just something that can take somewhat reliable and believable readings in perhaps the ~$50 range.Are multimeters with thermal probes normally okay for such readings? Or are there other affordable thermometers that are intended for taking occasional measurements with a slightly higher QC than those cheap window thermometers?

author: tv84
author_rank: Super Contributor
timestamp: July 30, 2023, 10:45:00 am
content: A few weeks ago, a friend of mine bought this one and is very happy with it (he didn't bought calibration):https://www.termometros.com/en/ThermaGuard-high-precision-thermometer-for-fridge-monitorization-39.9-to-49.9%C2%BACBut above your price range...Don't forget to state what is your required precision.PS: You could buy a bunch of different $5 devices and see which ones you're happy with.

author: BeBuLamar
author_rank: Super Contributor
timestamp: July 30, 2023, 11:40:56 am
content: For the refrigerator 2-3 degrees off isn't all that bad. I think the main problem is that the thermometer would take a long time to get the correct reading.

author: Bud
author_rank: Super Contributor
timestamp: July 30, 2023, 01:06:50 pm
content: Check the datasheet for your multimeter what accuracy it claims for temperature mode with the stock sensor.

author: mycroft
author_rank: Regular Contributor
timestamp: July 30, 2023, 01:50:20 pm
content: You can use an interchangeable NTC with a specified accuracy better then 1/2 degree C and a DMM. For examplehttps://us.rs-online.com/product/littelfuse/pt103j2/72244625/. No need for calibration.

author: HighVoltage
author_rank: Super Contributor
timestamp: July 30, 2023, 02:04:46 pm
content: I had just bought this one on ebay and it works great.Comes with two transmitters for the inside of the fridge and a display for the outside.https://www.ebay.de/itm/133833736104

author: hpw
author_rank: Frequent Contributor
timestamp: July 30, 2023, 02:21:25 pm
content: Quote from: Freesurfer on July 30, 2023, 10:24:29 amWell, I had once an issue with Turkey Vino Fridge, as changing about 5c from min to max.So I used my digital LaserLine Steak ThermoTester. (-40c ... +250c, -40F...+ 482F)... but a bottle with water into fringe, let them cool and measured the water after a while. As the real temp within the wine/water.As I needed the real temperature within the water/bottle... that worked fine and finally exchanged with valued Fridge model and the temperature change dropped down to 1c or less.For temperature measurement on gear, I use my Multi-meter with a term-element as cheap and connect to Multi-meter as having a large temp range. Important, that the temperature tip gets good contact and do not coos dawn the DUT.My 2 cents

author: Wrenches of Death
author_rank: Regular Contributor
timestamp: July 30, 2023, 02:34:36 pm
content: Quote from: Freesurfer on July 30, 2023, 10:24:29 amYou're over thinking this. Just grab a quality brand stick thermometer in an aluminum tube. No moving parts, no batteries, and reliable as hell. I've had mine for at least forty years. It hasn't failed yet and will outlast me. It doesn't use colored alcohol, it uses mercury. Not much to go wrong. Mine was made by Taylor.I leave it in groove just inside the freezer door opening.WoD

author: audiotubes
author_rank: Regular Contributor
timestamp: July 30, 2023, 03:03:06 pm
content: Quote from: Freesurfer on July 30, 2023, 10:24:29 amI have a small handful of gear from these guys:https://www.thermoworks.com/products/and it's really excellent.Some of the interesting pieces they sell include thermal loggers with NIST traceable calibration and certification like thishttps://www.thermoworks.com/thermadata-wifi-vaccine-kit/They have quite a lot of products listed so maybe you will find something suitable near your price range.I have found the support very good also. When I send a question I get complete and helpful answers. They know their product line very well, what probes work with what devices etc.

author: IanB
author_rank: Super Contributor
timestamp: July 30, 2023, 03:23:12 pm
content: I second ThermoWorks. I have their basic fridge/freezer thermometer and have been very happy with it:https://www.thermoworks.com/rt801/

author: tunk
author_rank: Super Contributor
timestamp: July 30, 2023, 03:54:51 pm
content: You could try to calibrate your thermometer:https://www.google.no/search?q=thermometer+calibrate+ice+cube

author: BillyO
author_rank: Super Contributor
timestamp: July 30, 2023, 09:18:29 pm
content: Accuracy on DMM thermocouples are generally +/- (1%+1C). That will most likely be better than any cheap fridge thermometer.

author: IanB
author_rank: Super Contributor
timestamp: July 30, 2023, 09:39:08 pm
content: Quote from: BillyO on July 30, 2023, 09:18:29 pmThe accuracy on the ThermoWorks model I linked above is quoted at ±0.5°C. I doubt a typical DMM thermocouple would do better than that.In fact, I use such thermometers to check the accuracy of my thermocouples, since I find the variability of the various thermocouple and meter combinations in my possession can easily be 2-3 degrees.

author: BeBuLamar
author_rank: Super Contributor
timestamp: July 30, 2023, 09:53:30 pm
content: Quote from: BillyO on July 30, 2023, 09:18:29 pmThermoworks thermometers while not very expensive they are not cheap. They have some models that can read very quickly.

author: coppice
author_rank: Super Contributor
timestamp: July 30, 2023, 09:53:48 pm
content: Thermometer accuracy used to be pretty bad, even for some quite expensive ones. These days even a digital thermometer costing just a few dollars usually reads within 0.5C of another thermometer. They mostly compete on settling speed, rather than accuracy, these days. Even there, some cheap ones are getting pretty quick these days.