PBasic Math ( Resolved)

sam_sam_sam

Hi EveryOne

This is a project that I have been ·ask to do·by employer

As of right now I can not give all of the details.......................
................·but when the Project is done I will share with all of you on the Forum


I know that I have·This a another Post but this is a different question
http://forums.parallax.com/showthread.php?p=804156

http://forums.parallax.com/showthread.php?p=804554


Here is the problem that I now have

Silo Hold 50,000 Pounds need to keep track of usage need smallest error possible

I was using the Seconds */309 to get the Flow Rate··

300 Pounds of Sand
248 Seconds to run the·Sand out of hopper
Which give you 1.21 pound per sec or 72.6 per minute

So I took 256 x 1.21 = 309.76 rounded to 310

When you look at the total 5 hour and 24 from now you get an error and this is at 22838 pound I still need to go to 50,000 pounds

S = 22782· error of· - 46
P = 22856· error of··+ 18

Actual results are suppose to be 22838

B = P - s */ 128
A = P - B

Now if I use this I can narrow the error to

A = 22819 error of· - 19

How can I· narrow the error down can any one help



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··Thanks for any··that you may have and all of your time finding them

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Sam

Post Edited (sam_sam_sam) : 7/22/2009 1:24:40 PM GMT

Tracy Allen

Sam,

When I calculate 5 hours, 24 minutes into seconds I get 19440 seconds, and that times 1.209677419355 pounds per second is 23516 pounds. Where did you get 22838? And shouldn't it be 72.6 #/minute, not 272.6 #/minute?

Anyway, for better precision in PBASIC math use ** instead of */.

1.209677419355 = 1 + .209677419355
.209677419355 * 65536 = 13741

Then in PBASIC:
pounds = seconds + (seconds ** 13741)

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Tracy Allen
www.emesystems.com

Mike Green

You are making some simplifying assumptions and those accumulate over time to cause errors.

In particular, 300 / 248 = 1.2096771935+ pounds per second. That's a 0.03% error (roughly).
With a 22838 pound load, that's an error of 9 pounds. You've got other errors from your other
rounding, roughly the same amount (309.76 rounded to 310).

If you want more accurate results, you'll need to use higher precision arithmetic.
Tracy Allen (www.emesystems.com) has quite a bit of information on multiple precision arithmetic for Stamps.
Follow the "math" link at the bottom of the page.

sam_sam_sam

Tracy Allen

Thank You for all of your help in this Project

That did the trick· It now work great

Now I understand how to use the ** and */ in P Basic Math with a number· like (·1.21)

Mike Green

Thank You for your help as well



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··Thanks for any··that you may have and all of your time finding them

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Sam