Order Tray | Contact Us | Home | SIG Lists

[wxsig] T-238 Humidity Calibration

Robert McGwier rwmcgwier at comcast.net
Fri Sep 2 04:00:39 UTC 2005


Will:

Since you are using the 68HC908, I do not understand why serious 
tinkering with pots are necessary.   If you measured the sensor outputs 
with a sufficiently dense set of points (and this cannot be that many),  
an approximation to the exact "transfer function" from humidity reading 
to actual humidity should be easily derived.  The set of points stored 
and then all readings are run through this "calibration engine" to 
produce the actual reading.


What am I missing?

Bob
N4HY





Will Beals wrote:

>Ken:
>
>I have been avoiding tackling this issue for BP sensors.  It isn't just
>being lazy.  My concern is that it is already really hard to calibrate the
>BP sensor with the two pots that interact with eachother a lot.  Adding two
>more calibration points makes the interactions eight times worse!
>
>If there was a thread on the humidity sensor, I may have misfiled it under
>the BP issue, sorry.
>
>I am open to such an adjustment, but how would you calibrate it?  I remember
>when I first started fiddling with the humidity sensor and was thinking of
>calibrating it, I had no practical way of doing so.  100% wasn't too hard,
>but any other target value seemed much less accurate than the sensors specs.
>Russ had given me the formula of salt to water such that at equilibrium the
>air in a sealed container would be at different humidity values, but there
>was no way I could be more accurate than the sensors 5%.
>
>will
>
>-----Original Message-----
>From: wxsig-bounces at lists.tapr.org [mailto:wxsig-bounces at lists.tapr.org] On
>Behalf Of Ken Brown
>Sent: Thursday, September 01, 2005 1:41 PM
>To: TAPR Weather Station SIG Mailing List
>Subject: [wxsig] T-238 Humidity Calibration
>
>
>Several weeks ago someone mentioned trying to put a pot on the humidity
>sensor because they were reporting several percent too high.  I have the
>same problem and wondered if there was any news of success in calibration of
>the sensor.
>
>Ken, APRS weather station N5KUK
>
>
>
>_______________________________________________
>wxsig mailing list
>wxsig at lists.tapr.org
>https://lists.tapr.org/cgi-bin/mailman/listinfo/wxsig
>
>
>
>
>_______________________________________________
>wxsig mailing list
>wxsig at lists.tapr.org
>https://lists.tapr.org/cgi-bin/mailman/listinfo/wxsig
>
>
>  
>






More information about the wxsig mailing list