Comment by lmz
20 hours ago
How is that relevant for the average buyer (as much as these things have an average buyer anyway)? Precision, accuracy, and battery life is helpful info but the inner components are an irrelevant detail. It's not like having a high quality part prevents them from using it wrong anyway.
The datasheet gives you much better fidelity data than an N=1 test. You'll never know what the tolerance is if you're just looking at one unit. Presumably the average buyer cares if they expect the temperature sensor to be 5% off on the unit they buy. The accuracy of all of these sensors have ratings, but they are often just copying the value on one component and not even considering a stackup. Devils lie in details.
Regarding accuracy, it's been about a decade, but I did some embedded projects related to accurate temperature measurements back in the day. From what I recall, anything sensor that is < $100 or so is going to be 5% margin of error at the very best, and regardless of price, you're going to have to calibrate it and figure out the curves in your ADC, it's not going to be linear. Additionally, just the act of measuring will heat your sensor slightly so that will need to be taken into account as well.
In short, if you need less than a couple degrees of accuracy, it's going to take a bit of tinkering. I wouldn't trust a $1 sensor for a tropical fish tank, for example, but probably good enough for a home thermostat.
I've used these: https://sensirion.com/media/documents/213E6A3B/63A5A569/Data...
They claim accuracy of +-0.2 c across a wide temperature range and in my use they seem to be. easy to find on a support board for under $10
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The datasheet will gives you absolute best case scenario. Like current consumption in sleep mode, or what register to set for best accuracy. It does not mean the Firmware will do exactly that.
The datasheet gives you the 3 sigma worst case for accuracy.
For power consumption a system power tree needs to be constructed and that will set the bounds that firmware can achieve. That would be better than trusting the manufacturer but a real test is best.
> How is that relevant for the average buyer
Avg buyer wont read a token of tests before buying whats marketed best.the whole point in test like these is to provide non-average buyer with info average buyer doesnt care for.
Average buyer googles "best cheap zigbee temperature sensor" and reads this article.
People who read ingredients lists of food are a tiny, parochial subset of consumers and yet they strongly influence what is on shelves.
The average person doesn’t read Hacker News, so why does it exist, and why are you here in the comments?
Similar reasons: the intended audience isn’t the average person.