Freezer Thermometer (2022)

Looking for a simple freezer thermometer that has a range down to -6F. I want to be able to monitor current temps (does not have to be constant) and keep a history. I have a Visonic door sensor but they wont go lower than -1.6F

I am currently using a ProSensor that works well, but it will not integrate with SmartThings.

Most of the postings about this are years old, there has to be new tech.

Tech changes, but physics doesn’t, and most battery operated devices sold for inexpensive home automation are only spec’d for down to 0 degrees F. Or maybe down to -4 degrees F, since that’s -20 degrees C. (They may work below that, but they won’t be described by the manufacturer as doing so.)

If you’re willing to use a probe attached to a radio unit outside the freezer you can go much lower with good accuracy, but I know most people aren’t interested in that for regular home use.

Hopefully others will chime in with whatever battery powered sensors they’re currently using for freezer monitoring. :sunglasses:

I have a friend who uses Cao wireless sensor tags, which have amazing engineering (spec’d for down to -40 degrees F) and excellent range. But lots of potential negatives: a reputation for terrible customer service, they require their own hub, and while there was an integration with ST back in 2016, I don’t think it’s ever been updated, so now you might have to use IFTTT. So I just mention them for people looking for better precision and wider operating range than the usual home automation sensors.

And here’s the thread on the old integration:

Wireless Sensor Tags Integration

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Thank you for the Fast Response, the tag may be overkill for what I’m trying to do. I only need - 6 because of a requirement for storage of breast milk for one of my grandchildren. The ProSensor I mentioned uses two batteries instead of one, and they last several months while reporting near constantly. I’m surprised. The only problem with their software is it only reports to my phone and only when I’m within BT distance.

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did you actually put the Visonic (which model MCT-340? ) in the freezer and it stopped reporting less than -1.6F? That would be good to know.

The Centralite multi-sensors, Smartthings relabelled, circa 2016, take 2x AAAA (unusual), read down to at least -9F and up to 140F . They are probably a little rare now, but the Centrallite/Smartthings Open-Close Sensors also read temperature and seem to perform the same

I would avoid the newer generation# STS-MLT-250 , I had too many problems.

I see one of the old preferred first gen types on ebay,

otherwise I would try whatever you have lying around. These devices frequently operate outside of their printed ratings anyway. If it’s really important then put in a couple different ones.


I use a stock ST leak sensor in my freezer obviously not for the leak detection capabilities. I use to monitor the temp. It takes a CR2 battery and I haven’t changed it in over a year. Temp hovers around -5 all the time.


The -1.6F is from an MCT340E. It continues to report, but I know the temp is lower than that based on the ProSensor.

Which ST Leak Sensor? I have a Samsung Electronics ST-CEN-MOIS-1/F-WTR-US-2 using stock DTH and it does not display any tempertures.

Aeotec SmartThings SmartThings Water Leak Sensor, ZigBee, Battery Powered, Smart Home Hub Compatible


I am using a IRIS door and window sensor. My Freezer is reading 12 degrees F. I had a Sensitive Strip, but the battery didn’t last a year.

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Thanks for the info!

12 or -12?

I use an Iris V2 motion sensor in a deep freeze and and I have had readings down to -16 (the coldest I have seen it) without any problems. These are no longer manufactured so you would have to see what might be available on eBay.

Why is it always the good stuff that they discontinue? Thanks for the info.