Home 
Search 
Today's Posts 
#1




curve fitting a charging capacitor type curve
Hi all, Newbie to this forum, but need some excel help. I have collected a bunch of data from an object as it heats up. The curve is very similar to a capacitor charging current curve. In my case, manually trying to approximate this curve, I come up with a formula of y= (rise)*(1exp(time))+ambient. Is there a way in excel to fit a curve like this or do I need an aftermarket solution? I need something that will use the data points and perform calculations to determine the curve. Thanks, Sean  mcgradys  mcgradys's Profile: http://www.excelforum.com/member.php...o&userid=28806 View this thread: http://www.excelforum.com/showthread...hreadid=484942 
#2




curve fitting a charging capacitor type curve
mcgradys wrote:
Hi all, Newbie to this forum, but need some excel help. I have collected a bunch of data from an object as it heats up. The curve is very similar to a capacitor charging current curve. In my case, manually trying to approximate this curve, I come up with a formula of y= (rise)*(1exp(time))+ambient. Is there a way in excel to fit a curve like this or do I need an aftermarket solution? I need something that will use the data points and perform calculations to determine the curve. Thanks, Sean Have you tried to use the Solver? Set up a table with a column of empirical data, a column of calculated data using your equation, and a column with the square of the error between the two with a sum at the bottom. The calculated data needs to be calculated using spreadsheet cells to store each of the parameters you're trying to fit. Then ask Tools/Solver to minimize the sum of the column of squared errors by varying the paramater value cells. I suspect Solver will work pretty well with this kind of problem. Good luck... Bill 
#3




curve fitting a charging capacitor type curve
Sean, check out Chartool & Smooth_Curve_Bezier the smart guys at XLRotor have
developed, it leverages Excel's native chart smoothing capability to fit the curve. It's free too. http://xlrotor.com/resources/files.shtml Cheers...Terry "mcgradys" wrote: Hi all, Newbie to this forum, but need some excel help. I have collected a bunch of data from an object as it heats up. The curve is very similar to a capacitor charging current curve. In my case, manually trying to approximate this curve, I come up with a formula of y= (rise)*(1exp(time))+ambient. Is there a way in excel to fit a curve like this or do I need an aftermarket solution? I need something that will use the data points and perform calculations to determine the curve. Thanks, Sean  mcgradys  mcgradys's Profile: http://www.excelforum.com/member.php...o&userid=28806 View this thread: http://www.excelforum.com/showthread...hreadid=484942 
#4




curve fitting a charging capacitor type curve
Assuming your data is in xvalu and yvalu
xvalu yvalu yvalu2 yvalu3 k_ast k_diff k_rc k_amp 0 0.0104 2.5896 0.0000 2.6000 0.0273 0.2057 2.6273 1 0.4459 2.1541 0.4885 2 0.8011 1.7989 0.8862 3 1.1477 1.4523 1.2100 4 1.3927 1.2073 1.4735 5 1.6954 0.9046 1.6881 6 1.9086 0.6914 1.8627 7 1.9831 0.6169 2.0049 8 2.0567 0.5433 2.1206 9 2.2272 0.3728 2.2148 10 2.2512 0.3488 2.2915 11 2.3140 0.2860 2.3540 Name all columns. Guess what your asymptote is and enter into k_ast. Enter into the yvalu2 column =k_astyvalu Enter into k_rc, k_amp, k_diff respectively =LN(INDEX(LOGEST(yvalu2,xvalu),1)) =INDEX(LOGEST(yvalu2,xvalu),2) =k_astk_amp Do a Goal Seek to set k_diff to zero by changing k_ast Your best fit curve is in yvalu3 =k_amp*(1EXP(k_rc*xvalu)) 
#5
Posted to microsoft.public.excel.misc




curve fitting a charging capacitor type curve
if you know time and are trying to fit rise and ambient, then the
function is linear in the unknowns and you can simply use SLOPE and INTERCEPT (or LINEST, if you prefer). In that case, your X column for fitting would be the calculated value =1exp(time) Jerry mcgradys wrote: Hi all, Newbie to this forum, but need some excel help. I have collected a bunch of data from an object as it heats up. The curve is very similar to a capacitor charging current curve. In my case, manually trying to approximate this curve, I come up with a formula of y= (rise)*(1exp(time))+ambient. Is there a way in excel to fit a curve like this or do I need an aftermarket solution? I need something that will use the data points and perform calculations to determine the curve. Thanks, Sean 
Reply 
Thread Tools  Search this Thread 
Display Modes  


Similar Threads  
Thread  Forum  
Fitting a curve similar to capacitor charging current.  New Users to Excel  
trend for polynomial curve fitting by regressing  Excel Worksheet Functions  
best curve fitting  Charts and Charting in Excel  
curve fitting to a sine function  Charts and Charting in Excel  
watch a curve change over time like a movie  Charts and Charting in Excel 