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Calibrate ds18b20 temp sensors? - Printable Version

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Calibrate ds18b20 temp sensors? - ottow - 2017-02-27

Hi,

I've connected a number of ds18b20 temp sensors via a DS9490R adapter, and got it all plotting data as described here:
http://www.tiarora.no/plott-av-vind-og-temperaturer/


I am however seeing about 1-2 C in variation between the sensors, and was wondering if there is any way to calibrate them? Hoping the error is linear I figured it may be possible to simply introduce an offset for a particular sensor, but I can see no such option in OP.

I was under the impression these things came calibrated but it seems I may have bought too cheap ones or something...

Thanks,

Otto

RE: Calibrate ds18b20 temp sensors? - SkipperEarly - 2017-02-28

When you use node-red and the dashboard you can simply make a function (like for the conversion degree K>C) into the flow where you add/sub a fixed value.

Had noticed the same particularity to measure up to 5deg difference with cheap sensors.

hope this helps.

RE: Calibrate ds18b20 temp sensors? - ottow - 2017-02-28

(2017-02-28, 06:35 AM)SkipperEarly Wrote: When you use node-red and the dashboard you can simply make a function (like for the conversion degree K>C)  into the flow where you add/sub a fixed value.

Had noticed the same particularity to measure up to 5deg difference with cheap sensors.

hope this helps.

Thanks, need to look into this.

RE: Calibrate ds18b20 temp sensors? - e-sailing - 2017-03-01

You are using v0.8!
In v0.9 you can set the offset of 1w sensors directly and you can use node-red.

RE: Calibrate ds18b20 temp sensors? - ottow - 2017-03-01

I see. Have to check out 0.9 when it is released then.

RE: Calibrate ds18b20 temp sensors? - PaddyB - 2017-03-02

Interesting. I've always found the DS18B20 chips to be very accurate - how far out are they? Have you tried them in iced water/boiling water?

Sent from my SGP511 using Tapatalk

RE: Calibrate ds18b20 temp sensors? - ottow - 2017-03-02

In my case, a couple of C, not much more. Most are very close to each other, but some are clear outliers.
I only noticed because I made a lab-setup at home and started plotting temperatures. Had all the sensors on the table essentially on top of each other but the plot showed clearly some of them where giving different values.
I suppose that's what you get when buying cheap eBay China sensors. Quality control? Naaa....