Topic: SHT30 vs SHT31

[galfert]

Very nice work. Thank you. Is there a way for you to test high humidity say 95% to 100% humidity with the SHT30 and SHT31?

[idahowx]

Looks like a solution of potassium nitrate or potassium sulfate is needed to get in to 90%+ RH range.  Based on the initial results with NaCl, it appears that the salt purity is critical for accuracy.  I initially used table salt without iodine but it has an anti-caking ingredient.  The RH was around 72% for table salt instead of 75% I got with larger and purer salt crystals.   The humidity reading for the WH31E responds very slowly compared to the Sensirion board so a very stable humidity environment is needed.  The data collected so far shows that the WH31E is fine for typical indoor temperatures and humidities.

Another possible project of interest is to replace the SHT31 on a Sensirion board with a SHT85.  It does not look to be very difficult mechanically using the flex connection.  That could provide interesting data for a possible outdoor sensor upgrade. 

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[HankR]

  Based on the initial results with NaCl, it appears that the salt purity is critical for accuracy.  I initially used table salt without iodine but it has an anti-caking ingredient.  The RH was around 72% for table salt instead of 75% I got with larger and purer salt crystals.   

Curious what the "larger and purer" actually was.  A little more detail please.

I have a household kind of salt that may meet the standards required to approximate the 75% result and it isn't Kosher contrary to conventional wisdom that that flavor of salt is unadulterated.  It is not.

Thanks for all your temp and humidity comparative tests.  I know it has taken some time, care, and effort.

The improved sensor came in with a very respectable reading at -10 C.

Hank