Recording temperatures–questions

[Eli N]

Many of the places I hike are distant from any weather station and at higher elevations, and I’d like to know what temperatures I’m actually experiencing so I can calibrate my clothing and gear choices. I found some old threads in which the Kestrel Drop sensors seem to be highly regarded, but it looks like they don’t record temperatures below 14°F.

So instead I ordered a SensorPush HT1, which claims to measure down to -40°F (although with less accuracy below freezing). I received it today and while it works, I was surprised by how long it takes to register temperature changes. When I took it from my heated apartment and left it outside (it’s around 35°F here), it took more than half an hour for the readings (taken every minute) to gradually drop to match the real outdoor temperature.</span>

Is this avoidable? Are the Kestrel Drops or any other available sensors more responsive? On the trail, if I’m ascending and the sun is going down, or if a cold front is coming in, the real temperature could easily change more quickly than this sensor can register it, which means it’s less reliable a record than I’d hoped for. I contacted the manufacturer and they blamed the mass of the device–but it’s only 40g, mostly plastic, so it’s hard to see how it could have much thermal mass.

[David Thomas]

The more material around the sensor, the slower the response will be.  30 minutes seems like a really slow response, though.  Ones that have an external sensor – one on a wire – would respond more quickly.  Some of those are really inexpensive, like $10.

Search for “indoor outdoor thermometer”.

If you leave the “indoor” unit inside your tent, you can see what’s happening without getting up.  And the indoor one will show what your sleeping bag experienced.  Run the wired, outdoor one out of the tent and it will reflect more radiant cooling, if it has a view of a clear night sky and could be 10F or more colder (which the outside of your sleeping bag would have been as well, had you slept under a clear sky.

[David Thomas]

Then’s the old-school approach: a min-max analogy thermometer.  The mercury pushes a magnetic marker to high and low limits (two different thermometers) and you reset it manually with a magnet.

The markers in this photo haven’t been reset – one is up by the red “MAX” and the other is above the blue 40 on the MIN scale.  They both show up better from a slightly different angle.  $29 on Amazon, although others are around $10.  Read the reviews.  Some models seem to be legitimately crappy while others are well regarded by some while not by others (there’s lots of possible user error and the fluid can separate in transit and most people don’t how to correct that).

All things considered, I’d focus on digital options and dig into the specifications for weights or at least size.

[Ken Thompson]

Better forecasts here

https://spotwx.com

[David Thomas]

I have found value in having a thermometer along, mostly to answer the question, “Why was I SO cold last night?” and the answer is usually that the temperature dropped 15F.  Wind and high humidity (such as along a stream) are potential confounders that a dry-bulb thermometer won’t capture.  Or radiant cooling, but a thermometer left out under the night sky will capture that effect.

[Rex Sanders]

In this video review the Kestrel Drop D1 takes about 30 minutes to cool down from 67 F to 39 F, and about 15 minutes to warm back up again:

The non-logging thermometers I’ve used have a significant lag time, too.

You might find this BPL article and comments useful:
https://backpackinglight.com/backpacking-with-thermometer-sanders/

In my experience, a thermometer in the sun, or buried in a white pack on a sunny day, registers much too high versus a “real” weather thermometer and felt experience. I find them most useful for tracking overnight temperatures to see how my shelter/sleep systems perform.

— Rex

[Mark Verber]

I don’t have a kestrel.. but have used a <span data-sheets-value=”{"1":2,"2":"Brunton ADC Pro WeatherStation"}” data-sheets-userformat=”{"2":11201,"3":{"1":0},"9":0,"10":2,"11":3,"12":0,"14":[null,2,0],"16":10}”>Brunton ADC Pro WeatherStation for the last 15 years or so. I find that it registers temp change within a few minutes.  I found iButton temp loggers to be fairly responsive, but have no built in display.</span>

[Andre W]

1. This is what I use to log temps. Havent noticed slow response to temp change, but I can do some test later..

[Renais A]

I took a Blue Maestro disc on my AT thru this year, and found it accurate, reasonably quick responding and easy to use.  The disc weighs about 13 grams, and records temperature, pressure and humidity.  It has an 18000 point data memory, easy to use Bluetooth interface and can record in intervals from 1 second to 24 hours.  I generally kept the disc in the side of a hip belt pocket where it did not see much of either my body warmth or the sun.  The app it uses allows for an easy download to an excel spreadsheet, or other formats, and viewing various graphs of the data is trivial.  The claimed accuracy is 0.5 F, 4% RH.  It is possible to insert calibration offsets which I did using a calibrated thermometer.  However, from the factory the temperature was within about 1.5 F, as I recall.  I set the system to only transmit data on demand, thereby eliminating all the power spent on constant Bluetooth contact.  With a 30 second recording interval I could get many weeks of data before needing to download.

Since I was hiking the AT I enjoyed seeing all the mountains and gaps reflected in the barometric data along with the temperature changes.  I generally kept the disc in a waterproof bag, so I didn’t have humidity data which reflected reality.  It was also fun to watch the arrivals of high and low pressure fronts as I went along.  Temperature range is -40 F to 185 F.  You can set it to send alarms if desired, and if you want continuous phone visibility that is possible, but battery life is undoubtedly lowered.  The battery is a 2032, easily replaceable.  I’ve had my unit for 11 months and it still shows a strong battery.

Renais

[Rex Sanders]

Renais – thanks for pointing out the Blue Maestro discs, look good for another project I’m working on.

For Eli, from the Bluemaestro.com web site:

Temperature Response Time:
Time to 63% of final value in response to step change 3.8 minutes. Actual response time will vary dependant on system thermal mass and air flow

— Rex

[Kyle]

What about a sunto core watch? I have the same desire to record temp, and this seems like a good option. It can log temp, humidity, and pressure.

SUUNTO Core All Black Military Men’s Outdoor Sports Watch – SS014279010 https://www.amazon.com/dp/B001DCEKXM/ref=cm_sw_r_em_apa_i_7Cb6Db3VZ7G21

[Roger Caffin]

A watch will record your wrist temperature, not the ambient.

Cheers

[Kyle]

That is the case if you wear it,  but most people I see with this watch just strap it onto their pack.

[Roger Caffin]

I cut the heavy straps off (they restricted blood flow in the cold of the snow fields) and hung it around my neck so I could check altitude whenever.

Cheers

[Eli N]

Thank you for all the information–this has been very helpful. I think I will try one of those Blue Maestro discs–it’s encouraging that they publish the response time.

[Andre W]

It took about 11 mins to go from 79f to 9f (in the freezer) and about 12 mins to go back to 79f. Record interval set to 1min. This is using the Inkbird Mini, weighs 10g including battery. I think it is decent response time.

The blue maestro stuff looks really good, too.

[Ben H.]

A bit of an industrial answer, but you will get much faster response times:

https://www.omega.com/en-us/control-and-monitoring-devices/data-loggers/p/OM-20A-TC-Series

and pair it with a t-type thermocouple:

https://www.omega.com/en-us/sensors-and-sensing-equipment/temperature/sensors/thermocouple-probes/qd-mini-not-molded/p/SCPSS-020G-6

 

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