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# HDC2021: Comparison of temperature read by HDC2080 and HDC2021

Part Number: HDC2021
Other Parts Discussed in Thread: HDC2080,

Dear Team,

We are using the temperature and humidity sensors from TI in one of our design. We have produced 50 boards with HDC2021 and 50 with HDC2080. We have observed that the boards with HDC2080 are reading on an average 0.8°C higher than HDC2021. Can we know what are the reasons for the difference in reading the temperature? However no difference is observed in Humidity reading. Below images give the details of the temperature read by 1 HDC2080 board and 1 HDC2021 board. This log was taken continuously for 4 hours in room temperature. Similar response was observed with other boards as well.

Kindly give us feedback and probable cause for the difference soon. It is important to adjust the offset in our sample accordingly

• Dear Surabhi -

Thanks for the post and welcome to E2E!

What voltage are you operating the device at and are you using the formula for converting the digital output to C, from the HDC2080 DS?

page 18 (https://www.ti.com/lit/ds/symlink/hdc2080.pdf) I found when running from 3.3VDC, for example, using -40.62 at the end of that equation gave me the best results.

• Dear Josh,

Thank you for your response. We are operating sensors at 3V and formula we are using as below.

Value received is raw, will be corrected according to formula present on datasheet

Temperature (in degrees)=((rawTemperature) / (2^16))*165.0 - 40.0

Thank you

• Dear Surabhi -

For HDC2080, use ...-40.62 (in datasheet)

For HDC2021, use ...-40 (in datasheet)

• Dear Josh,

Thanks for the hint. Datasheet has been updated. Another question,

As mentioned by you, for HDC2080 we need to use -40.62 and in the data sheet it shows -40.5. Are you using PSSR equation to improve the accuracy and mentioning the -40.62 information?

•  Dear Surabhi -

if you are running at 3.3VDC, -40.62 is the number. -40.5 was a compromise. :)

• Dear Josh,

Thanks. Can we know more details about PSSR? Why is it not mentioned in HDC2021 data sheet?

• Surabhi -

the C/V spec is in the HDC2021 DS (page 5) - what I told you about here has nothing to do with that spec really - for the HDC2080 the difference in the formula was caused by a internal test procedure mistake (human error).