Can you crack this formula with a PIC ?
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Posts: 46,084
It's a formula to calculate water vapour pressure given a temperature in Deg C
float calculateWaterWVP(float Temp)
{
float a,tempInK,c,d,e,wvp;
tempInK = Temp + 273.15;
a = -6096.9385 * (1/tempInK);
c = -2.711193 * 0.01 * tempInK;
d = 1.673952 * 0.00001 * (tempInK * tempInK);
e = 2.433502 * (log(tempInK)/log(10)/0.434294509);
wvp = exp(a + 21.2409642 + c + d + e);
return wvp;
} */
If you can do this, you get a medal !
Regards,
Darren
float calculateWaterWVP(float Temp)
{
float a,tempInK,c,d,e,wvp;
tempInK = Temp + 273.15;
a = -6096.9385 * (1/tempInK);
c = -2.711193 * 0.01 * tempInK;
d = 1.673952 * 0.00001 * (tempInK * tempInK);
e = 2.433502 * (log(tempInK)/log(10)/0.434294509);
wvp = exp(a + 21.2409642 + c + d + e);
return wvp;
} */
If you can do this, you get a medal !
Regards,
Darren
Comments
The PAK-I doesn't do log and exp, but the PAK-II does.
http://www.al-williams.com/awce/pak1.htm (has info on PAK-I and II).
You can also read the manuals online and see some examples in the doclib.
Regards,
Al Williams
AWC
*8 channels of PWM: http://www.al-williams.com/awce/pak5.htm
>
Original Message
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> Sent: Thursday, October 26, 2000 11:21 AM
> To: picbasic-l@q...; PICLIST@m...;
> basicstamps@egroups.com
> Subject: [noparse][[/noparse]basicstamps] Can you crack this formula with a PIC ?
>
>
> It's a formula to calculate water vapour pressure given a
> temperature in Deg C
>
> float calculateWaterWVP(float Temp)
> {
> float a,tempInK,c,d,e,wvp;
>
> tempInK = Temp + 273.15;
> a = -6096.9385 * (1/tempInK);
> c = -2.711193 * 0.01 * tempInK;
> d = 1.673952 * 0.00001 * (tempInK * tempInK);
> e = 2.433502 * (log(tempInK)/log(10)/0.434294509);
>
>
> wvp = exp(a + 21.2409642 + c + d + e);
> return wvp;
>
> } */
>
> If you can do this, you get a medal !
>
> Regards,
> Darren
>
>
I've tried to do this sort of math MANY times with my weather
station, and have been mostly unsucessful. I'd highly recommend
using Al Williams' PAK module to do it.
It *is* possible to do with just the Stamp/PIC, but you'd
likely end up with an inprecise answer.
Matt Parnell
Parnell Engineering, LLC http://www.weatherstamp.com
37637 Five Mile Rd., #198 mail@w...
Livonia, MI 48154-2634 Phone: (734) 464-0150
Fax: (734) 432-9866 ICQ: 14074347
Pager: (517) 251-7674
Original Message
From: DAZLOGAN@a... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=ctWTMVrpvJMy4MdaUAHnnSihr0z2RXn7f92y-oh1qLm3lM6dXTOhGK46h28D5DdZimPTDp-jXtnz1sE]DAZLOGAN@a...[/url
Sent: Thursday, October 26, 2000 12:21 PM
To: picbasic-l@q...; PICLIST@m...;
basicstamps@egroups.com
Subject: [noparse][[/noparse]basicstamps] Can you crack this formula with a PIC ?
It's a formula to calculate water vapour pressure given a temperature in Deg
C
float calculateWaterWVP(float Temp)
{
float a,tempInK,c,d,e,wvp;
tempInK = Temp + 273.15;
a = -6096.9385 * (1/tempInK);
c = -2.711193 * 0.01 * tempInK;
d = 1.673952 * 0.00001 * (tempInK * tempInK);
e = 2.433502 * (log(tempInK)/log(10)/0.434294509);
wvp = exp(a + 21.2409642 + c + d + e);
return wvp;
} */
point math is easier to process. If you need an example of fixed point math
let me know.
MH
Original Message
From: "Matt Parnell" <tparnell@o...>
To: <basicstamps@egroups.com>
Sent: Thursday, October 26, 2000 4:52 PM
Subject: RE: [noparse][[/noparse]basicstamps] Can you crack this formula with a PIC ?
> Hi Darren,
>
> I've tried to do this sort of math MANY times with my weather
> station, and have been mostly unsucessful. I'd highly recommend
> using Al Williams' PAK module to do it.
>
> It *is* possible to do with just the Stamp/PIC, but you'd
> likely end up with an inprecise answer.
>
> Matt Parnell
> Parnell Engineering, LLC http://www.weatherstamp.com
> 37637 Five Mile Rd., #198 mail@w...
> Livonia, MI 48154-2634 Phone: (734) 464-0150
> Fax: (734) 432-9866 ICQ: 14074347
> Pager: (517) 251-7674
>
>
Original Message
> From: DAZLOGAN@a... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=dtXo9aibgKt-mp7iwONQ4u9U_-ylW13PX8WleSbqQIUujeexUBSu4qnd6uVPwNZ1DAGEz-g4Fg]DAZLOGAN@a...[/url
> Sent: Thursday, October 26, 2000 12:21 PM
> To: picbasic-l@q...; PICLIST@m...;
> basicstamps@egroups.com
> Subject: [noparse][[/noparse]basicstamps] Can you crack this formula with a PIC ?
>
>
> It's a formula to calculate water vapour pressure given a temperature in
Deg
> C
>
> float calculateWaterWVP(float Temp)
> {
> float a,tempInK,c,d,e,wvp;
>
> tempInK = Temp + 273.15;
> a = -6096.9385 * (1/tempInK);
> c = -2.711193 * 0.01 * tempInK;
> d = 1.673952 * 0.00001 * (tempInK * tempInK);
> e = 2.433502 * (log(tempInK)/log(10)/0.434294509);
>
>
> wvp = exp(a + 21.2409642 + c + d + e);
> return wvp;
>
> } */
>
>
>
>
Deg C
> float calculateWaterWVP(float Temp)
> {
> float a,tempInK,c,d,e,wvp;
> tempInK = Temp + 273.15;
> a = -6096.9385 * (1/tempInK);
> c = -2.711193 * 0.01 * tempInK;
> d = 1.673952 * 0.00001 * (tempInK * tempInK);
> e = 2.433502 * (log(tempInK)/log(10)/0.434294509);
> wvp = exp(a + 21.2409642 + c + d + e);
> return wvp;
> } */
>If you can do this, you get a medal !
Hi Darren,
The medal would have to be real geld to get cracking seriously on that one!
Then, the first questions would be, over what temperature range, and to
what accuracy? Is it pure water--there are big effects from salts. If you
want it only near 25'C then, linearize around 3.169 kpa. Larger range--a
table lookup with interpolation? Get out the big money to attempt to crack
the formula!
-- Tracy Allen
electronically monitored ecosystems
http://www.emesystems.com