tag:blogger.com,1999:blog-4922503085503427986.post4170533455900086555..comments2024-03-29T00:14:30.842-07:00Comments on Desert Home: Acurite Console Barometer: OK, This is it.davehttp://www.blogger.com/profile/11608589214882334649noreply@blogger.comBlogger13125tag:blogger.com,1999:blog-4922503085503427986.post-75920784490106360302015-02-22T15:40:06.575-07:002015-02-22T15:40:06.575-07:00I used the -I and -L parameters to the compiler to...I used the -I and -L parameters to the compiler to do the same thing. Also, it depends on the compiler version what includes are needed, I just happened not not need one for memcpy. Otherwise, it wouldn't have compiled and I would have had to add it.davehttps://www.blogger.com/profile/11608589214882334649noreply@blogger.comtag:blogger.com,1999:blog-4922503085503427986.post-37223643505340473072015-02-22T13:00:48.311-07:002015-02-22T13:00:48.311-07:00Great work Dave! Been playing and tweaking with y...Great work Dave! Been playing and tweaking with your stuff for a few weeks now.<br /><br />The libusb kicked my tail. For my Pi, I did need to:<br /> - Add a file to "/etc/ld.so.conf.d/" called it, stupidLibusb.conf<br /> - Added a line "/usr/local/lib" to it (only line)<br /> - Ran ldconfig to grab the new conf file and it worked.<br /><br />Also, looking at your getweather.c program, it looks like it's missing a "#include " so it can take advantage of the memcpy.<br /><br />Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-4922503085503427986.post-79288122294620775622015-02-21T08:28:45.109-07:002015-02-21T08:28:45.109-07:00Dave,
I live in a transition zone between subtropi...Dave,<br />I live in a transition zone between subtropical and temperate climate.<br />I found the algorithm performance to be satisfactory, except in summer, when it constantly predicts rain in the middle of sunny dry spells.<br />I understand this is because a simple glitch in the rule, which makes it too sensitive for small pressure changes. I imagine this must ruin the whole forecast in a location where dry spells are the rule.Robertohttp://www.robertopellanda.com.brnoreply@blogger.comtag:blogger.com,1999:blog-4922503085503427986.post-52685118235952725482015-02-21T07:58:25.293-07:002015-02-21T07:58:25.293-07:00I haven't looked at the forecast algorithm, bu...I haven't looked at the forecast algorithm, but for me, it's always wrong. That's a substantial thing here in Arizona where it's sunny 340 days a year.davehttps://www.blogger.com/profile/11608589214882334649noreply@blogger.comtag:blogger.com,1999:blog-4922503085503427986.post-67943361001718604932015-02-21T05:29:28.334-07:002015-02-21T05:29:28.334-07:00Hi,
I have an acurite wx station here in Brazil an...Hi,<br />I have an acurite wx station here in Brazil and I have been trying to figure out how the forecast algorithm works.<br />Since I don't understand anything about hardware/software like you guys I have been trying a "rudimentary" approach which is to make time lapses movies of the display and then try to figure how the icons respond to the various changes in the parameter readings.<br />I was wondering if you think it is possible and if you tried to analise directly the code which rules the forecasting algorithm.<br />Thanks!<br />RobertoRobertohttp://www.robertopellanda.com.brnoreply@blogger.comtag:blogger.com,1999:blog-4922503085503427986.post-34877527391688086832015-02-20T09:30:28.352-07:002015-02-20T09:30:28.352-07:00No, it was inside at all times. I meant to imply t...No, it was inside at all times. I meant to imply that a) the outside temperature has no effect, so the reading is not already compensated for air density, b) the inside temperature has no effect, so the reading is already compensated for the sensor's intrinsic temperature sensitivity, therefor the reading can be relied upon as an absolute pressure, and software should apply altitude and barometric calculations.Anonymoushttps://www.blogger.com/profile/10104744220495560133noreply@blogger.comtag:blogger.com,1999:blog-4922503085503427986.post-59133240775814749072015-02-19T18:16:08.914-07:002015-02-19T18:16:08.914-07:00Did you take the console outside? I didn't tr...Did you take the console outside? I didn't try that, since it was plugged into the raspberry pi and I would have had to cart it and an extension cord.davehttps://www.blogger.com/profile/11608589214882334649noreply@blogger.comtag:blogger.com,1999:blog-4922503085503427986.post-19695356257174119542015-02-19T15:42:03.776-07:002015-02-19T15:42:03.776-07:00Pressure remained linear across significantly diff...Pressure remained linear across significantly different indoor and outdoor temperatures, leading me to believe that the values reported should be interpreted as absolute pressure. I let weewx take care of calculating the barometric pressure from that and my altitude, although I had to add a fixed fudge factor to that value to align with NWS.Anonymoushttps://www.blogger.com/profile/10104744220495560133noreply@blogger.comtag:blogger.com,1999:blog-4922503085503427986.post-87038748341178365242015-02-19T13:24:16.162-07:002015-02-19T13:24:16.162-07:00That is an absolutely awesome calculator, it could...That is an absolutely awesome calculator, it could have saved me a ton of time on various projects over the years. <br /><br />I pretty much just dumped the console barometer data I collected. Once I saw it was within a fraction a a mbar, I called it good and moved on to something else. If I'm within a fraction and all I'm really interested in is the trend over the last hours, that's good enough. Especially since I keep my doors open and a breeze through the house will change it more than that due to temperature, <br /><br />Although, it could be possible to decode the temperature, and factor it into the reading. But then we're trying to overcome the shortcomings of the console with an approximation.<br /><br />The data set for a couple of days is still up on Xively, but getting it back could be a pain. If you want it, I will give it a try and pass it on. The data comes back to me as a JSON string in multiple parts that have to be taken apart and combined.davehttps://www.blogger.com/profile/11608589214882334649noreply@blogger.comtag:blogger.com,1999:blog-4922503085503427986.post-72296901828579421592015-02-19T11:10:46.448-07:002015-02-19T11:10:46.448-07:00I used this calculator to find the best fit after ...I used this calculator to find the best fit after using a spreadsheet to determine that it was indeed linear:<br /><br />http://www.alcula.com/calculators/statistics/linear-regression/Anonymoushttps://www.blogger.com/profile/10104744220495560133noreply@blogger.comtag:blogger.com,1999:blog-4922503085503427986.post-29729876196094413012015-02-19T11:04:50.760-07:002015-02-19T11:04:50.760-07:00I tried to reply to the earlier post a couple of t...I tried to reply to the earlier post a couple of times, but nothing happened, so I moved on :)<br /><br />The precision is from a linear best fit based on 24 sampling points. It has a very high correlation factor, so I don't want to arbitrarily remove precision. However, with your much larger dataset, maybe we could come up with a better fit and more confidence in the significant digits.Anonymoushttps://www.blogger.com/profile/10104744220495560133noreply@blogger.comtag:blogger.com,1999:blog-4922503085503427986.post-2331442164149112142015-02-18T11:43:01.082-07:002015-02-18T11:43:01.082-07:00And you didn't tell me ???
The level of preci...And you didn't tell me ???<br /><br />The level of precision you're using is way too much, there's a lot more error in there than the number of digits to the right of the decimal you're using. And, I could get the correlation even closer by using a successive approximation to get the best offset and slope, but it isn't necessary. <br /><br />What's needed is a good reading so that the up or down trend can be established for a reliable weather change indicator.<br /><br />Remember to keep the console at a relatively stable temperature.<br /><br />Now, when I have the time I may try out the temperature formula you gave me. Once again, it's an academic exercise for me since I have temperature sensors in place already and am building more.<br /><br />Thanks for the update, We still need the battery level of the weather head though.davehttps://www.blogger.com/profile/11608589214882334649noreply@blogger.comtag:blogger.com,1999:blog-4922503085503427986.post-67503001919074770962015-02-18T09:33:35.915-07:002015-02-18T09:33:35.915-07:00This is pretty close to what I figured out for wee...This is pretty close to what I figured out for weewx (scaling for mbar included in the slope):<br /><br />p = 0.062424282478109 * d1 - 206.48350164881<br /><br />where d1 = ( R2[23] << 8 | R2[24] )<br /><br />I had a correlation factor of > 0.99 with a handful of manual readings from a calibrated pressure gauge (absolute pressure, not barometric).<br /><br />I calculated something similar for inside temperature:<br /><br />t = 0.049538214503151 * d2 - 1801.189704931<br /><br />where d2 = ( R2[21] << 8 | R2[22] )<br /><br /><br />I might borrow your constants and see how close it looks.Anonymoushttps://www.blogger.com/profile/10104744220495560133noreply@blogger.com