If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#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)*(1-exp(-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)*(1-exp(-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)*(1-exp(-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_ast-yvalu Enter into k_rc, k_amp, k_diff respectively =LN(INDEX(LOGEST(yvalu2,xvalu),1)) =INDEX(LOGEST(yvalu2,xvalu),2) =k_ast-k_amp Do a Goal Seek to set k_diff to zero by changing k_ast Your best fit curve is in yvalu3 =k_amp*(1-EXP(k_rc*xvalu)) |
#5
|
|||
|
|||
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 =1-exp(-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)*(1-exp(-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 |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
trend for polynomial curve fitting by regressing | vijaya | Worksheet Functions | 7 | November 11th, 2005 03:51 PM |
best curve fitting | ladee_bird | Charts and Charting | 1 | September 20th, 2005 07:25 AM |
curve fitting to a sine function | Tenarife | Charts and Charting | 2 | August 13th, 2005 08:23 PM |
watch a curve change over time like a movie | RandyBarrett | Charts and Charting | 6 | February 19th, 2005 05:00 AM |
Normal Curve Fitting | sjromaine | Charts and Charting | 2 | May 4th, 2004 04:46 PM |