Si Labs SI7051 temperature sensor looks interesting

[mmagin]

So I was thinking of building my own thing to log temperatures from multiple sensors, and being that I don't have much of a way to calibrate them, I was thinking I wanted something with reasonable accuracy already.

So this is an I2C temperature sensor which comes from the factory accurate to +/- 0.1C, and it's $2 at digikey.  Tiny 6-DFN package.

(Edit, link: https://www.silabs.com/Support%20Documents/TechnicalDocs/Si7050-1-3-4-5-A20.pdf )

Any caveats or reasons I should be more skeptical of this?

[DTJ]

That's an interesting part. I couldn't see any graphs of the temp accuracy v measured temp.


The 0.1°C accuracy is over a very narrow range.

Data sheet p7:

±0.1 °C: +35.8 °C to 41 °C;
±0.13 °C: 20.0 °C to 70.0 °C;
±0.25 °C: –40 °C to +125 °C

Looks like its aimed at medical thermometers.
http://www.silabs.com/Support%20Documents/TechnicalDocs/AN1026-Si70xx-Temp-Sensor-Designers-Guide.pdf
I wonder what it's like over the range say -10°C to 60°C.


Check out the TSYS01 its +/-0.1 over a wider range but costs 3x more.

[mmagin]

Ooh, good catch.  That'll teach me to read the footnotes more carefully!

[Asim]

I used SI7021 temperature & humidity sensor in a pcb I designed. i liked it to the point where it is my go to sensor

[beeryt]

Found this sensor as well and thinking of using it. Extrapolating from the ranges provided the -10°C to 60°C should be between ±0.13°C and ±0.25°C.

I'm not sure if I'm nimble enough to solder the 6-DFN package though. Especially given the sensitivity of the sensor and the strong recommendation to reflow.

[mycroft]

There is a (new) digital temperature sensor from TI: TMP117 (http://www.ti.com/lit/ds/symlink/tmp117.pdf).

Specs are ±0.1°C (Maximum) From –20°C to +50°C

[SiliconWizard]

I've used the Si7051 in a couple projects and it's a fine sensor. It has an integrated CRC block, so you can verify the digital integrity of each measurement. The small DFN package may look intimidating for hand soldering, but it's actually pretty easy to deal with.

Of course we'd need to know what your exact application is, and what kind of accuracy you are after.

One thing to consider is the way you mount the sensors on the PCB, especially if you intend on measuring ambient temperatures. Depending on what's around them and more generally what's on the PCB, they will tend to measure an higher temperature than the ambient temperature due to small local heating. Errors of 1°C are not uncommon at all even if your circuit doesn't generate much heat. One way to work around this is to add slots around each sensor to limit heat propagation. Failing to take such proper counter-measures will completely defeat the point of using a relatively high accuracy sensor.