On Wed, Jul 13, 2011 at 11:45 AM, Paul Alfille <[email protected]> wrote: > Honeywell has updated and simplified their datasheets. I use the formula > straight from the datasheet: > http://sensing.honeywell.com/index.cfm/ci_id/142534/la_id/1/document/1/re_id/0 > Voltage output (1st order curve fit) VOUT=(VSUPPLY)(0.0062(sensor RH) + > 0.16), typical at 25 ºC > Temperature compensation True RH = (Sensor RH)/(1.0546 – 0.00216T), T in ºC > > Earlier versions also had a complicated quadratic temperature compensation > (2nd order curve fit), which I used for a while (and documented in that web > page). Since they don't publish the parameters for the 2nd order curve fit > any more, and the datasheet graphs look pretty straight to me, I've gone > with these. > One issue is the offset voltage (0.16V) in the formula. Willy Robinson > tested the (earlier) HIH3600 and stated that the offset should be scaled to > supply voltage as well, rather than being a fixed offset as in this formula. > We do that for the HIH3600, but I have no reason to change the Honeywell's > specifications for the HIH4000 without some actual measurements. The Datanab > people also use a fixed offset in their HIH4000 calculations.
The code is the authoritative source then, that's great. I need to find a good outside reference to calibrate all these sensors to. Hopefully that can unravel some of these mysteries. Any suggestion for the wrong read problem? Pedro ------------------------------------------------------------------------------ AppSumo Presents a FREE Video for the SourceForge Community by Eric Ries, the creator of the Lean Startup Methodology on "Lean Startup Secrets Revealed." This video shows you how to validate your ideas, optimize your ideas and identify your business strategy. http://p.sf.net/sfu/appsumosfdev2dev _______________________________________________ Owfs-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/owfs-developers
