Thanks again. I am sensing all the three sensors available i.e. temperature , light and humidity. I use the following formulas ,
temperature = (float)(-39.6 + 0.01*(float)val); humidity = (float)(-2.0468 + 0.0367*(float)val + 0.00000159*(float)(val*val)); but when I use MsgReader tool to read the data, I always get temperature as 29.0 or like that when I view it on PC and when I send to the database, it automatically converts it into int and gives value as 29. Other thing is at the start the first value is always zero for all the three sensors. I cannot understand how can I use these sensors to get values and add some precision to it... Regards, Mayank On Fri, Jun 10, 2011 at 7:00 PM, Michael Schippling <sc...@santafe.edu> wrote: > Assuming that the readings you are getting are, > as I suggested, the raw ADC values from 0-4095 > you can convert them to a voltage by multiplying > by the ADC's reference voltage -- nominally 3.3v. > So a 0 value is equal to 0 volts and a full scale > 4095 value is equal to 3.3v. The reading you get > is some fraction in between those: > > (value / full-scale) * refVolts > > example, if your value happens to be 2000: > > (2000 / 4095) * 3.3 == 1.6117 volts > > I would take the last couple digits with a grain > of salt because the system is usually pretty noisy, > and I'm not really bright enough to figure out if > the theoretical precision is 3 or 4 decimal points > anyway. > > Now your sensor may need some calibration and scaling > so the conversion you use will probably have a form > like (Mx + B), where M is a scale factor and B is an > offset, both of which you might derive from spec sheets > or brute force measurements. > > What are you sensing anyway? > MS > > > Mayank Gupta wrote: >> >> Thanks for the help Michael. But again I am not really sure how to do >> that. >> Can you refer me to some tutorial or reading where I can see how to >> actually code it.. Sorry but not really getting it. >> >> Regards, >> Mayank >> On Fri, Jun 10, 2011 at 5:13 PM, Michael Schippling <sc...@santafe.edu> >> wrote: >>> >>> Pretty much all sensors readings on TOS devices are >>> integer values directly from the ADC -- some few, like >>> Voltage, may be may be mangled for range and level >>> but are probably also ints. IIRC the telosb has a 12 >>> bit converter so you should have 0-4095 as your values, >>> which is a resolution of about .00025 per bit. You may >>> convert that to floating point to about 4 decimal places >>> if you like. >>> >>> MS >>> >>> Mayank Gupta wrote: >>>> >>>> Hi all, >>>> >>>> I am sending sensor readings from telosb mote to the pc and storing >>>> the data in mysql database. The problem I am facing is that I want >>>> data to be precise upto at least 2 decimal places but data in my >>>> database always comes out to be as integer. I have modified the mig >>>> generated file to push data into the database rather than show output >>>> on the screen. I hope someone can guide me in the right direction so >>>> that I can get more precise value in my database. >>>> >>>> Regards, >>>> Mayank >>>> _______________________________________________ >>>> Tinyos-help mailing list >>>> Tinyos-help@millennium.berkeley.edu >>>> https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help > _______________________________________________ Tinyos-help mailing list Tinyos-help@millennium.berkeley.edu https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
