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perhaps bringing in the station to test it in a controlled environment to determine the difference between the sensor and the standard.

How much of a difference if the sensor is removed from the chamber and tested vs.  one of the current 3 prime locations in the chamber.

This is why I bark at you for parachuting into the thread and not bothering to do the least bit of reading. If you had read page 14, for instance, you'd see that Ron had run extensive tests in his humidity chamber and reproduced the wet bias. Then again, Ron's results from his laboratory-grade instrument are just another of 420 "opinions" right?
Would you please leave me alone.  Why do you seem to think you are in charge here.   I have reported you to the moderators and  definitely they need to step in and quell your hatred toward me and anything I ask .  Just leave me alone. Stop harassing me.
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perhaps bringing in the station to test it in a controlled environment to determine the difference between the sensor and the standard.

How much of a difference if the sensor is removed from the chamber and tested vs.  one of the current 3 prime locations in the chamber.

This is why I bark at you for parachuting into the thread and not bothering to do the least bit of reading. If you had read page 14, for instance, you'd see that Ron had run extensive tests in his humidity chamber and reproduced the wet bias. Then again, Ron's results from his laboratory-grade instrument are just another of 420 "opinions" right?
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They surely don't come close to meeting the claimed specs when it counts.

Just looking again at Davis' NIST traceable doc (link posted above) and it says they verify humidity to be within +/- 3% between 33% and 90% with the checkpoints being 33%, 80% and 90%. Please notice they skip testing the most common middle ranges.

Once again, the question arises: at what temperature(s) are they testing humidity? They don't say. You could assume they use the temperature checkpoints, but I don't like assuming.

So even if you pay to have the humidity certified, we still don't know if the device is accurate in the most problematic middle ranges.
4
After 4 days with 2 new sensors, my conclusion they aren't much better than the old still running high on DP at those critical levels when its important to be most accurate (high heat index).

So basically I have 2 new sensors both now reach 98%.. Whoopie!  I'm beginning to think these sensors are just off. They surely don't come close to meeting the claimed specs when it counts.

I guess a key question is the temp at which Sensirion tests the sensors' humidity spectrum. My guess would be 25C (77F) since I see mention of it along with 63% in the notes on their datasheet. If they aren't testing beyond that, then, indeed, there could be discrepancies elsewhere.

I guess we should’ve paid attention to the “maximum accuracy” on Sensirion’s spec sheet. Lol

No kidding.. :sad:
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perhaps bringing in the station to test it in a controlled environment to determine the difference between the sensor and the standard.

Davis has been moving the location of that sensor.   Initially it was fastened to the bottom of one of the radiation plates, but they moved it to the top of the next plate up because water was  collecting just enough that it saturated the sensor. Now if you have a FARS, as I do, the unit is mounted on its side in the chamber. 

How much of a difference if the sensor is removed from the chamber and tested vs.  one of the current 3 prime locations in the chamber.
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After 4 days with 2 new sensors, my conclusion they aren't much better than the old still running high on DP at those critical levels when its important to be most accurate (high heat index).

So basically I have 2 new sensors both now reach 98%.. Whoopie!  I'm beginning to think these sensors are just off. They surely don't come close to meeting the claimed specs when it counts.

I guess a key question is the temp at which Sensirion tests the sensors' humidity spectrum. My guess would be 25C (77F) since I see mention of it along with 63% in the notes on their datasheet. If they aren't testing beyond that, then, indeed, there could be discrepancies elsewhere.

I guess we should’ve paid attention to the “maximum accuracy” on Sensirion’s spec sheet. Lol
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Here is Earth Networks (formerly WeatherBug) spec sheet for their stations. Will note that their DPs matches up well with ASOS stations
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After 4 days with 2 new sensors, my conclusion they aren't much better than the old still running high on DP at those critical levels when its important to be most accurate (high heat index).

So basically I have 2 new sensors both now reach 98%.. Whoopie!  I'm beginning to think these sensors are just off. They surely don't come close to meeting the claimed specs when it counts.

I guess a key question is the temp at which Sensirion tests the sensors' humidity spectrum. My guess would be 25C (77F) since I see mention of it along with 63% in the notes on their datasheet. If they aren't testing beyond that, then, indeed, there could be discrepancies elsewhere.
9
I know IDT HS 3001 spec sheet says that it can go out of spec if it’s in high humidity conditions for a long time but I’m curious if it would behave the same way as the Sensirion sensors would or not?

I do know that the VP2 can’t take IDT’s sensor but I’m curious to how it would perform compared to Sensirion’s sensors.
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I’m getting the feeling that it doesn’t matter if you have the SF2 filter or not, the SHT-31 is going to have a wet bias during the daytime hours.

I'm starting to get that impression too. jerryg initally stated with such confidence that the SF2 had kept his sensors accurate. The readings you posted would suggest otherwise.

I also recall Ron's (kcidwx) statement about heat ultimately being the only way to prevent too much moisture sitting against the sensor.

However, that makes one wonder why it is Rainwise sensors don't fall victim to this same problem?

The only other idea I have is to calibrate the humidity on the console. That will work fairly well until the humidities get closer to 100% (late 80s & 90s).

My tests, purely from the field involving 2 sensors of differing age, indicate the sensor's bias point crosses over somewhere in the 70 percentiles. Meaning, the 70s are the range where the sensor is least positively or negatively biased. Below that, once a sensor is out of specification, I've observed a wet bias (at least down to the 30% range - haven't been able to test below that). Above that starting around 80%, there's a dry bias that worsens as you approach 100% (although technically within spec).

The departures both in DP and humidity are worse when it's warm (above 80), but shows up when it's cooler too. Currently, my good sensor reads 63/47 and my bad sensor reads 64/50. That's a 3% humidity difference in the mid 50 percentiles. Still out of spec on the older sensor, but not nearly as bad as when it gets warmer. When it's in the 80s/90s and midrange humidities, I'm seeing 5-8% and 4-5 deg DP departures between the two sensors.
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