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enjoyneering / HTU21D

This is an Arduino library for HTU21D, Si7021 and SHT21 Digital Humidity & Temperature Sensor
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Temperature compensated humidity for SHT21 #2

Closed Diederikvanderpant closed 6 years ago

Diederikvanderpant commented 7 years ago

Hi,

What is your source for the temperature compensation of the humidity at line 418 in HTU21D.CPP . You claim it is valid for the SHT21 but I cannot any reference in the Sensirion datasheets for the SHT21.

Sincerely, Diederik vd Pant

enjoyneering commented 7 years ago

Good question.

The HTU21D datasheet from 2014, see row "Temperature coefficient" in the table on page 3.

Diederikvanderpant commented 7 years ago

Hi,

Thanks for the answer! Out of curiosity. How did you find out that HTUD21D from MEAS and SHT21 from Sensirion are identical? Googling, it seems a lot of people know about this. But their datasheets do not mention each other....

Sincerely,

Deiderik

2017-04-12 14:03 GMT+02:00 enjoyneering notifications@github.com:

Good question.

The HTU21D datasheet from 2014, see row "Temperature coefficient" in the table on page 3.

— You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub https://github.com/enjoyneering/HTU21D/issues/2#issuecomment-293555748, or mute the thread https://github.com/notifications/unsubscribe-auth/AI2mTkQjKUj49Sxsdn0ZUJpkKbY9Q3Qtks5rvL2DgaJpZM4M6GDX .

enjoyneering commented 7 years ago

Hi, Deiderik

Take a look at Grath 1 on p. 4 of HTU21D datasheet and Figure 2 on p.2 of SHT21 . They are identical, plus returning the same chip ID, see readDeviceID() function.

The Si7021 is completely different beast. It's RH accuracy a little bit better, Figure 2 on p.8. And it looks like it does temp. compensation automatically, see readTemperature(HTU21D_TEMP_READ_AFTER_RH_MEASURMENT)). You have to call it after RH measurement.

All three sensors are very accurate and reliable, however if you just starting the project I'am suggesting BME280. See the article.

Diederikvanderpant commented 7 years ago

Hi, Thanks for the quick reply. Will use your code in a testsetup with sht21's i am running. Btw in another setup i am also very satisfied with the performance of sht31 and bme280 who have Tcompensation integrated. Sincerely, Diederik

Op 12 apr. 2017 17:56 schreef "enjoyneering" notifications@github.com:

Hi, Deiderik

Take a look at Grath 1 at p. 4 of HTU21D datasheet and Figure 2 at p.2 of SHT21 . They are identical, plus returning the same chip ID, see readDeviceID() function.

The Si7021 is completely different beast. It's RH accuracy a little bit better, Figure 2 at p.8. And it looks like it does temp. compensation automatically, see readTemperature(HTU21D_TEMP_READ_AFTER_RH_MEASURMENT)). You have to call it after RH measurement.

— You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub https://github.com/enjoyneering/HTU21D/issues/2#issuecomment-293624366, or mute the thread https://github.com/notifications/unsubscribe-auth/AI2mTvtdavfRuntj_PkWgY-HTbZ9ST_Wks5rvPQpgaJpZM4M6GDX .