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Comment by AlotOfReading | Hacker News Reader

No, it's pretty easy to get better sensors than that. E.g. a cheap-ass SHT20 will do +-0.3C. In fact, my own automotive parts recommendations are the next grades up (SHT21/SHT3x) as standard for my employer's boards because the cost difference is justified.

Never underestimate the ability of a manufacturer to select subpar parts to save 25 cents on the BOM and spend 6 figures elsewhere trying to fix the resulting issues though.

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I think the problem is not the accuracy of the sensors themselves but that its difficult to have a placement inside the car such that the measurement is minimally influenced. Many factors influence temperature: heat from the motor, from heating and from the sun shining on the car and perhaps others.

And it also depends what exactly you want to measure: air, motor or inside temperature? People might get confused. And inside temperature might differ a lot: behind the windscreen it might be a lot hotter than at the floor.

No, you read the datasheet wrong. It's +/- 3C.

I'm looking at the datasheet right now. Relative humidity accuracy tolerance is +-3.0, temperature is +-0.3. Different tables.

I imagine the temperature gradient across the car might be +/- 3degC, ignoring the actual sensor.

It's undoubtedly more than that, depending on where you measure. The gradient between e.g. the roof lining and the AC vent could easily be 20C+ degrees on a hot day. Most boards on a vehicle will have their own temperature sensors to measure enclosure temps, and there will be zonal sensors at various points in the cabin as well. The climate control loop will be defined in terms of those zonal sensors.

Measuring temperature is not trivial. There's convective, conductive and radiative heat transfer and they all factor into the measurement. And that may not accurately reflect the "cabin temperature," particularly in a parked car.

But the weird part is that OEM seem to be fine with that variation when it comes to climate control. Do they use multiple temp sensors?

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