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MFJ259 conversion help
On Thu, 05 Dec 2013 14:42:02 -0600, John S
wrote: On 12/5/2013 1:49 PM, John S wrote: Well I did it using an old dirty trick: adding one fake data point at the end to bend the curve. http://img560.imageshack.us/img560/1845/yi2.gif You must then not use the values which are above the last valid data point. You may program this formula into an Arduino .-) w. Yes, the trend line is very close. But, please perform a calculation on the 498R value using the equation and let me know if it agrees. If yours does, then something is wrong here. Thanks, John Helmut - Please see this. I think Excel is screwed up. https://imageshack.com/i/mrg919p Yes, you are right. Although EXCEL calculated the curve correctly in its own diagram, it outputs false (rounded) parameters for the curve fitting polynom. Compare with the Graphmatica plot, they are ident. Have to find out tomorrow how to get the polynom factors without rounding errors, if possible. http://img834.imageshack.us/img834/8177/altv.gif w. |
#2
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MFJ259 conversion help
On 12/5/2013 4:38 PM, Helmut Wabnig wrote:
On Thu, 05 Dec 2013 14:42:02 -0600, John S wrote: On 12/5/2013 1:49 PM, John S wrote: Well I did it using an old dirty trick: adding one fake data point at the end to bend the curve. http://img560.imageshack.us/img560/1845/yi2.gif You must then not use the values which are above the last valid data point. You may program this formula into an Arduino .-) w. Yes, the trend line is very close. But, please perform a calculation on the 498R value using the equation and let me know if it agrees. If yours does, then something is wrong here. Thanks, John Helmut - Please see this. I think Excel is screwed up. https://imageshack.com/i/mrg919p Yes, you are right. Although EXCEL calculated the curve correctly in its own diagram, it outputs false (rounded) parameters for the curve fitting polynom. Compare with the Graphmatica plot, they are ident. Have to find out tomorrow how to get the polynom factors without rounding errors, if possible. http://img834.imageshack.us/img834/8177/altv.gif w. I found these coefficients at a site called ZunZun dot com: y = a + bx + cx2 + dx3 + fx4 + gx5 Fitting target of lowest sum of squared absolute error = 7.0645972802275931E-06 a = 3.3214807109861584E-02 b = 7.2539508790925885E-04 c = -3.2830626216867792E-06 d = 7.9094355769986563E-09 f = -9.4574857953126017E-12 g = 4.3679252922923517E-15 Worst case error is .202% at 50. John |
#3
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MFJ259 conversion help
On Fri, 06 Dec 2013 03:57:40 -0600, John S
wrote: On 12/5/2013 4:38 PM, Helmut Wabnig wrote: On Thu, 05 Dec 2013 14:42:02 -0600, John S wrote: On 12/5/2013 1:49 PM, John S wrote: Well I did it using an old dirty trick: adding one fake data point at the end to bend the curve. http://img560.imageshack.us/img560/1845/yi2.gif You must then not use the values which are above the last valid data point. You may program this formula into an Arduino .-) w. Yes, the trend line is very close. But, please perform a calculation on the 498R value using the equation and let me know if it agrees. If yours does, then something is wrong here. Thanks, John Helmut - Please see this. I think Excel is screwed up. https://imageshack.com/i/mrg919p Yes, you are right. Although EXCEL calculated the curve correctly in its own diagram, it outputs false (rounded) parameters for the curve fitting polynom. Compare with the Graphmatica plot, they are ident. Have to find out tomorrow how to get the polynom factors without rounding errors, if possible. http://img834.imageshack.us/img834/8177/altv.gif w. I found these coefficients at a site called ZunZun dot com: y = a + bx + cx2 + dx3 + fx4 + gx5 Fitting target of lowest sum of squared absolute error = 7.0645972802275931E-06 a = 3.3214807109861584E-02 b = 7.2539508790925885E-04 c = -3.2830626216867792E-06 d = 7.9094355769986563E-09 f = -9.4574857953126017E-12 g = 4.3679252922923517E-15 Worst case error is .202% at 50. John Yes, that's better neither EXCEL nor OPEN OFFICE can do it correctly. Excel generates the correct formula, but outputs only truncated or rounded coefficients. I do not know how to access the internal correct coefficients in Excel. Then I found this site: http://www.xuru.org/rt/PR.asp#CopyPaste Which outputs the following: http://img43.imageshack.us/img43/6194/jmph.jpg Which gives the correct curve when inserted into EXCEL with some editing. =4,368089718E-15*(B4)^5-9,457445532E-12*(B4)^4+0,000000007909410217*(B4)^3-0,000003283056669*(B4)^2+0,0007253920186*(B4)+0,03 321499593 http://img547.imageshack.us/img547/1012/o8io.gif To improve the curve fitting I suggest to take additional measurements in the upper range. w. |
#4
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MFJ259 conversion help
On 12/6/2013 4:27 AM, Helmut Wabnig wrote:
On Fri, 06 Dec 2013 03:57:40 -0600, John S wrote: On 12/5/2013 4:38 PM, Helmut Wabnig wrote: On Thu, 05 Dec 2013 14:42:02 -0600, John S wrote: On 12/5/2013 1:49 PM, John S wrote: Well I did it using an old dirty trick: adding one fake data point at the end to bend the curve. http://img560.imageshack.us/img560/1845/yi2.gif You must then not use the values which are above the last valid data point. You may program this formula into an Arduino .-) w. Yes, the trend line is very close. But, please perform a calculation on the 498R value using the equation and let me know if it agrees. If yours does, then something is wrong here. Thanks, John Helmut - Please see this. I think Excel is screwed up. https://imageshack.com/i/mrg919p Yes, you are right. Although EXCEL calculated the curve correctly in its own diagram, it outputs false (rounded) parameters for the curve fitting polynom. Compare with the Graphmatica plot, they are ident. Have to find out tomorrow how to get the polynom factors without rounding errors, if possible. http://img834.imageshack.us/img834/8177/altv.gif w. I found these coefficients at a site called ZunZun dot com: y = a + bx + cx2 + dx3 + fx4 + gx5 Fitting target of lowest sum of squared absolute error = 7.0645972802275931E-06 a = 3.3214807109861584E-02 b = 7.2539508790925885E-04 c = -3.2830626216867792E-06 d = 7.9094355769986563E-09 f = -9.4574857953126017E-12 g = 4.3679252922923517E-15 Worst case error is .202% at 50. John Yes, that's better neither EXCEL nor OPEN OFFICE can do it correctly. Excel generates the correct formula, but outputs only truncated or rounded coefficients. I do not know how to access the internal correct coefficients in Excel. Then I found this site: http://www.xuru.org/rt/PR.asp#CopyPaste Which outputs the following: http://img43.imageshack.us/img43/6194/jmph.jpg Which gives the correct curve when inserted into EXCEL with some editing. =4,368089718E-15*(B4)^5-9,457445532E-12*(B4)^4+0,000000007909410217*(B4)^3-0,000003283056669*(B4)^2+0,0007253920186*(B4)+0,03 321499593 http://img547.imageshack.us/img547/1012/o8io.gif To improve the curve fitting I suggest to take additional measurements in the upper range. w. Together, I think we got a reasonable answer. Thanks for your information. I did not know about adding an additional data point to help the curve. Nice work. |
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