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How accurate is the temperature sensor?
I am using twine in my wine cellar to measure temperature..however, compared to my existing equipment which measures both ambient and in bottle temps, the ambient temp on twine seems a few degrees low which may make sense because it is inside the case. What benchmarks / lab tests have you done confirm temp. accuracy? In most applications 1 or 2 degrees is acceptable but not in a wine cellar...would love to connect an in bottle temp probe to my twine to improve accuracy within .5 degree. My current cooling unit keeps the cellar within .75 degrees at all times and want to use twine as a backup in case that sensor fails....
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19 Comments sorted by Votes Date Added
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A man with two thermometers never knows what temperature it is! The cover will slow down how Twine's temperature reading adjusts to changes, but it should get to the right temperature. There's little variation between Twines. Note that if temperature will go up a few degrees if you're in setup or fast mode - communication makes Twine work harder.
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In between bug chasing, we're writing real documentation for each sensor. I'll be sure to include that setup and fast mode drive the temperature up. But in normal operation Twine uses a minuscule amount of power, and won't create an amount of heat outside the margin of error.
Answers
Oregon Scientific THN132N - 78.8°
Oregon Scientific THGR122NX - 78.4°
Smarthome INSTEON Wireless Thermostat (2441ZTH) - 80°
Twine - 75°
I even took off the cover to see if that would make a difference - doesn't appear to. All 4 are sitting literally inches apart. Not sure what to make of that.
Twine = 71%
pretty close. wonder how thisvaries from Twine to Twine
Edit: reading is now 64F which is only a 0.3 difference with the room thermostat. That's pretty good!
In another thread the developers have acknowledged the problem with the Celsius rule, so presumably it will get fixed.
There is also a granularity issue. If you are working in Fahrenheit, your accuracy is almost twice what it is in Celsius, because the Twine reports only in whole number degrees. Thus, if your "trigger" temperature needs to be fairly accurate, working in Fahrenheit is preferable.
Right now, my Twine is reporting 74 F, and a mercury in glass chemical lab thermometer is reading 23.9 C (=75 F). This kind of thermometer comes with and accuracy of +/-0.2 C. For the picky, the thermometer bulb is right beside the middle of the Twine's bottom, and the Twine is resting on its "right". (I have no idea where the temperature sensor is actually located on the Twine circuit board.)
So roughly speaking, my Twine is reporting about 1 F low, at these particular conditions. (Note that the Twine could actually be reading 74.49 F, which would round down to the displayed 74 F, and the actual temperature could actually be 23.7 C (=74.7 F.)
Since most users will probably use the temperature for much cruder decisions than would require fractional degree accuracy (has my furnace died and my house temperature gone below 45 F; or, has my freezer stopped working and is about to thaw food), in engineering terms, my Twine (at least my Twine) is close enough for practical purposes.