@mvader I haven't made any very accurate temp testings. But the readings are exactly the same than other non-sensbender devices in my home. I started researching the humidity b/c I had different readings between different devices.
Temp looks fine to me.
@bjacobse Yes I have 3 sensbener running from 2 different orders. All 3 are very near by each other. So at 33% they all read something near to 40%.
I have 4 more sensbenders to build. However I continue to test tonight with a Boveda-Pack that claims to bring the hum in a containter to exactly 69%. I did 4 test's so far and also used different technics. So i get more and more confident.
But the very good thing is - it looks every reproducible. So the value may be off but reproducable accurate off by about 8%. When I completed my test it will be very easy to correct it within the software.
@bjacobse Yes and no 
Yes 100% is outside of the spec.
And no. 33% with Magnesium Chloride Hexahydrate is inside the spec and I get 40% instead of 33-34%.
Max off should be 3% above or? Means 37% - but fair enough. Should be ok for household use.
But I tested tonight with distilled water - so should be exactly 100%. And again (I didn't know that thats possible) I got 104 and 107% so slightly above (still increasing). Thats great b/c that means all values are about 7-8% too high.
At 33% the reading was about 40%
At 75% the reading was about 83%
At 100% the reading was about 106%
So reading minus 8% gives a pretty accurate result. In the next few days i will test 3 more sensbender.
Distilled Water (100% expected):
@tbowmo No I haven't baked yet. I will try that but not in the next two weeks. But I will report back.
@tbowmo I'm now almost sure that my test-setup has no faults very reproducable and read many articles - I plan to verify my findings with someone who has a professional calibrated device.
I saw in a museum nearby that they have professional calibrated devices
So I will test against those
@tbowmo Good hint. But it is happening to all three sensbeners for at least one month now. (different orders). I now got 4 more so I will test again soon.
Over xmas I tested also with magnesium chloride hexahydrate. magnesium chloride hexahydrate produces exactly 33%rel.
All 3 sensbenders report exactly 39% or 40%. So they are also here 7% off. But almost the same value and very reproducible - so thats great!
In the new year I will test with "Magnesium chloride". It brings the rel humitity to exactly 32% - I will report how that goes
Yes it looks like that the sensors are 8% off. I tested the other way around >opening at ~100rel and closing and same + exactly back to 82/83 and it should be 75% :-).
@Dwalt
Thanks for the info. I'm currently opening the box every several hours to test the salt soup. My room has something between 50 and 60 rel. (so below 75). And every time I open the box this (see pic). It drops and goes back up to 82 or 83. Than it stabilizes there over the next couple hours. There are two sensbenders in the box - thats what the two line are. And yes they are remarkable equal. But it always goes to 82 - i would hope for 75. But I will repeat this procedure until it starts to stabilizes after every opening a little bit below the value that was there before the opening. Because if that happens i am below the dry point and than I will test in a room with humidity higher than 80 and test if soup can do the same into the other direction and holds it stable for many openings. THAN i know that the salt is performing is job correctly and know that the test is good and the senbender is wrong or hopefully I learn the opposite.
@tbowmo Thanks. No worries the electronic won't touch the salt or water. The salt/water is just within the same closed container to bring the enclosed air to exactly 75.3% rel hum (at 25C).
I followed this howto: But there are many other similar ones.
http://www.kingofthehouse.com/hygrometer/
Did someone "test" the humidity precision of the Si7021on the sensbender? Of corse the datasheet says max 3% off but how reliable is that?
I have other sensors here and they differ by about 10%. So I did a "Salt-Calibration-Test" and there my two sensbenders or better Si7021 are 6% over the reference value. They report 81% and it should be 75%.
Note: It's my first time that I performed this test and I'm not 100% sure that the (water-salt-ratio) is correct - thats why I'm interested if someone else tested the values?
I have the same Issue 
But with all my NRF's. They all consume about 5mA while Idle. Any new thoughts on this issue?
