I have the original version of the Photon Weather Shield with the HTU21D humidity sensor. I followed the same project and code from the repository here - https://learn.sparkfun.com/tutorials/ph … rticle-ide
Everything seems to be fine and all the readings from the different sensors including the wind and rain meters with the exception of the humidity. The humidity always reads -6.00% no matter what the weather is like.
Any ideas of what could be wrong here? A bad HTU21D sensor on the shield maybe?
Thanks!
Hi Tim.
Are you sure you’re using the right tutorial for your board? If your shield has a Si7021 on it rather than the HTU21D you can see odd humidity values being reported. Check the back of the board to see what version you have. It sounds like you might be using the V10 tutorial with the V11 board.
Hey Chris. I have the V10 shield with the HTU21D and best I can tell I am going off of the tutorial and code for it. What i am trying to determine is are there two separate versions of the Sparkfun_Photon_Weather_Shield Library? It appears that the same library supports both the HTU21D and Si7021 sensors.
Hi Tim,
The library should work with both sensors since it runs a check on the I2C bus for which address is present and adjusts for that. I would be surprised if your temperature readings were accurate from the HTU21D but your humidity readings are off. Can you confirm the temperature readings are accurate? Also, has the humidity reading ever been accurate or has it only ever sent -6.00%?
I am going to test one of these here to see if something possibly changed in the Particle IDE that breaks the humidity readings. I expect that this is not the issue since we would have heard from other customers about that but it is worth checking.
Hi Mark,
All of the other readings seem to be fairly accurate, or at least a little more realistic. It has always only shows -6.00%. All that aside, I thought I remembered some time ago in a dumpster dive box getting another one in the box. I went digging around and sure enough did! Same V10 board with the HTU21D. I plugged the photon into it having made no modification to the code it is showing a more realistic reading in the 40% range and fluctuates a tad.
I can only assume that maybe the original shield (which I bought new long ago and just now got around to hooking up) has a bad sensor. The one from the Dumpster Dive box is ok. (That’s funny… sort of).
What do you think? I attached a picture of the two - the one with the photon is the working one.
Hi again Tim,
Well that is just strange. It definitely sounds like a defective HTU21D on the one Weather Shield. Especially since the Dumpster Dive board works with the same code and Photon. Assuming you purchased the Photon Weather Shield directly from SparkFun, fill out the form on [this page if you would like and we will follow up with instructions on how to proceed from there.](Return Policy - SparkFun Electronics)
Hi Mark
I appreciate the follow up. It has probably been close to a few years since I purchase it (from Sparkfun). I am not too worried about it. Incidentally I did end up ordering the V11 version. It seems to work just fine.
I did notice with the two different versions having two different humidity sensors, they seem to both measure about the same (which is off a little bit and I assume as others have mentions it is likely caused by heat coming off of the photon).
All is well anyhow. I appreciate your help! 
I have it up and running with the weather meters attached also.
Hi Tim,
Ah, that is good to hear the v11 shield is working just fine and you have a working weather station. We did our best with those sensors to isolate them from the rest of the components on the board to get accurate data but, as you have seen, the Photon runs pretty warm, especially when using the onboard WiFi. If it is a consistent error you can pretty easily account for it in your code by just adjusting the temp/humidity function(s) to subtract or add whatever error you measure.
Let us know if you have any other questions or concerns about this or any of our products and we would be happy to help.
Happy Hacking!
Mark I sort of did your suggestion. I have the station registered on Weather Underground and I am averaging the readings from surrounding stations over the course of several days. Then I will adjust the code accordingly. 
Thanks again!!
