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[MATHCAD] An amazing Plot, lost some points?

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[MATHCAD] An amazing Plot, lost some points?
Author: Peter Wehrli    Posted: Wed, 01 Sep 1999 15:16:54 +0200
Hello everybody, The attached file "switcher.mcd" contains a Bode plot of simple first order low pass filter (two resistor and a capacitor). Now I have the following Question: How it is possible, that plot depends on the x-range? that means if I change the right End of the plotrange from 10E8 to 10E10, the frequency respons in the plot at a frequency for example at about 10 E6 Hz is almost 20dB wrong!!! It seams to me, that there are not enough points in the plot.Does exist an option in Mathcad to fix that problem, or is it a nasty bug? Thank you for a good idea to solve this problem Peter Wehrli Zühlke Engineering AG CH-8952 Schlieren-Zürich e-mail: />

RE: [MATHCAD] An amazing Plot, lost some points?
Author: Robert Garner    Posted: Wed, 1 Sep 1999 15:43:48 +0100
I don't think it is a bug. You need to make the frequency (omega) a range variable. It then seems to work OK. Regards, Bob Garner ************************************************************************* Bob Garner CEng. (Mechanical Engineer) Interfleet Technology Ltd. Interfleet House, Pride Parkway, Derby, DE24 8HX email: /> ************************************************************************* > -----Original Message----- > From: Peter Wehrli /> > Sent: Wednesday, September 01, 1999 2:17 PM > To: /> > Subject: [MATHCAD] An amazing Plot, lost some points? > > Hello everybody, > > > The attached file "switcher.mcd" contains a Bode plot of simple first > order low pass filter (two resistor and a capacitor). > > Now I have the following Question: > > How it is possible, that plot depends on the x-range? that means if I > change the right End of the plotrange from 10E8 to 10E10, the frequency > respons in the plot at a frequency for example at about 10 E6 Hz is > almost 20dB wrong!!! > > It seams to me, that there are not enough points in the plot.Does exist > an option in Mathcad to fix that problem, or is it a nasty bug? > > Thank you for a good idea to solve this problem > > Peter Wehrli > Zühlke Engineering AG > CH-8952 Schlieren-Zürich > e-mail: /> > << File: switcher1.mcd >> ------------------------------------------------------------- The Mathcad List - Discussion, Support & News Contributions: /> To unsubscribe: Send in the body: unsubscribe mathcad To: /> Hosted by: Adept Scientific http://www.adeptscience.com List Archive: http://lists.adeptscience.co.uk/

RE: [MATHCAD] An amazing Plot, lost some points?
Author: Robert Garner    Posted: Wed, 1 Sep 1999 16:00:57 +0100
I don't think it is a bug. You need to make the frequency (omega) a range variable. It then seems to work OK. Regards, Bob Garner ************************************************************************* Bob Garner CEng. (Mechanical Engineer) Interfleet Technology Ltd. Interfleet House, Pride Parkway, Derby, DE24 8HX email: /> ************************************************************************* > -----Original Message----- > From: Peter Wehrli /> > Sent: Wednesday, September 01, 1999 2:17 PM > To: /> > Subject: [MATHCAD] An amazing Plot, lost some points? > > Hello everybody, > > > The attached file "switcher.mcd" contains a Bode plot of simple first > order low pass filter (two resistor and a capacitor). > > Now I have the following Question: > > How it is possible, that plot depends on the x-range? that means if I > change the right End of the plotrange from 10E8 to 10E10, the frequency > respons in the plot at a frequency for example at about 10 E6 Hz is > almost 20dB wrong!!! > > It seams to me, that there are not enough points in the plot.Does exist > an option in Mathcad to fix that problem, or is it a nasty bug? > > Thank you for a good idea to solve this problem > > Peter Wehrli > Zühlke Engineering AG > CH-8952 Schlieren-Zürich > e-mail: /> > << File: switcher1.mcd >> ------------------------------------------------------------- The Mathcad List - Discussion, Support & News Contributions: /> To unsubscribe: Send in the body: unsubscribe mathcad To: /> Hosted by: Adept Scientific http://www.adeptscience.com List Archive: http://lists.adeptscience.co.uk/

RE: [MATHCAD] An amazing Plot, lost some points?
Author: Diehl Ted-ETD012    Posted: Wed, 1 Sep 1999 11:29:37 -0400
Peter, Did you send this bug to Mathcad directly. It is important to do that to ensure they know about it and they can fix it. Ted Diehl Motorola -----Original Message----- From: Peter Wehrli /> Sent: Wednesday, September 01, 1999 9:17 AM To: /> Subject: [MATHCAD] An amazing Plot, lost some points? Hello everybody, The attached file "switcher.mcd" contains a Bode plot of simple first order low pass filter (two resistor and a capacitor). Now I have the following Question: How it is possible, that plot depends on the x-range? that means if I change the right End of the plotrange from 10E8 to 10E10, the frequency respons in the plot at a frequency for example at about 10 E6 Hz is almost 20dB wrong!!! It seams to me, that there are not enough points in the plot.Does exist an option in Mathcad to fix that problem, or is it a nasty bug? Thank you for a good idea to solve this problem Peter Wehrli Zühlke Engineering AG CH-8952 Schlieren-Zürich e-mail: /> ------------------------------------------------------------- The Mathcad List - Discussion, Support & News Contributions: /> To unsubscribe: Send in the body: unsubscribe mathcad To: /> Hosted by: Adept Scientific http://www.adeptscience.com List Archive: http://lists.adeptscience.co.uk/

RE: [MATHCAD] An amazing Plot, lost some points?
Author: Pergande, Albert N    Posted: Wed, 01 Sep 1999 14:29:05 -0400
You haven't defined omega anywhere other than as the pass parameter to functions A and G. In version 8, MathCAD takes a wild guess, usually 0 to 10 in steps of 0.1, when you plot a function without giving it a valid range variable. I recommend you create a range variable i with the number of points you want to plot, and make omega [ i a function of i and plot against it. Life will be much easier. -----Original Message----- From: Peter Wehrli /> Sent: Wednesday, September 01, 1999 9:17 AM To: /> Subject: [MATHCAD] An amazing Plot, lost some points? Hello everybody, The attached file "switcher.mcd" contains a Bode plot of simple first order low pass filter (two resistor and a capacitor). Now I have the following Question: How it is possible, that plot depends on the x-range? that means if I change the right End of the plotrange from 10E8 to 10E10, the frequency respons in the plot at a frequency for example at about 10 E6 Hz is almost 20dB wrong!!! It seams to me, that there are not enough points in the plot.Does exist an option in Mathcad to fix that problem, or is it a nasty bug? Thank you for a good idea to solve this problem Peter Wehrli Zühlke Engineering AG CH-8952 Schlieren-Zürich e-mail: /> ------------------------------------------------------------- The Mathcad List - Discussion, Support & News Contributions: /> To unsubscribe: Send in the body: unsubscribe mathcad To: /> Hosted by: Adept Scientific http://www.adeptscience.com List Archive: http://lists.adeptscience.co.uk/

Fw: [MATHCAD] An amazing Plot, lost some points?
Author: Ruben O Domenech    Posted: Fri, 3 Sep 1999 00:02:30 -0300
I think that you can get a clearer picture of what is happening if you format both plots selecting some symbol (as x's) instead of none in the 'traces' tag. By doing so, it looks like Mathcad has been using the following series of omega values to calculate points of G: 1, 10^7, 2*10^7, 3*10^7, 4*10^7 ... in the first plot, and 1, 10^5, 2*10^5, 3*10^5, 4*10^5 ... in the second one. I guess that Mathcad is trying to use 1000 points to give by default a (supposedly) fair representation of the function, but... with very poor fortune, because it uses points evenly spaced in a natural scale, while in the plot is specified to use a logaritmic one. I believe this is indeed a bug in Mathcad, and that it deserves to be fixed. ----- Original Message ----- From: Pergande, Albert N /> To: /> Sent: 1 de septiembre de 1999 15:29 Subject: RE: [MATHCAD] An amazing Plot, lost some points? You haven't defined omega anywhere other than as the pass parameter to functions A and G. In version 8, MathCAD takes a wild guess, usually 0 to 10 in steps of 0.1, when you plot a function without giving it a valid range variable. I recommend you create a range variable i with the number of points you want to plot, and make omega [ i a function of i and plot against it. Life will be much easier. -----Original Message----- From: Peter Wehrli /> Sent: Wednesday, September 01, 1999 9:17 AM To: /> Subject: [MATHCAD] An amazing Plot, lost some points? Hello everybody, The attached file "switcher.mcd" contains a Bode plot of simple first order low pass filter (two resistor and a capacitor). Now I have the following Question: How it is possible, that plot depends on the x-range? that means if I change the right End of the plotrange from 10E8 to 10E10, the frequency respons in the plot at a frequency for example at about 10 E6 Hz is almost 20dB wrong!!! It seams to me, that there are not enough points in the plot.Does exist an option in Mathcad to fix that problem, or is it a nasty bug? Thank you for a good idea to solve this problem Peter Wehrli Zühlke Engineering AG CH-8952 Schlieren-Zürich e-mail: /> ------------------------------------------------------------- The Mathcad List - Discussion, Support & News Contributions: /> To unsubscribe: Send in the body: unsubscribe mathcad To: /> Hosted by: Adept Scientific http://www.adeptscience.com List Archive: http://lists.adeptscience.co.uk/ ------------------------------------------------------------- The Mathcad List - Discussion, Support & News Contributions: /> To unsubscribe: Send in the body: unsubscribe mathcad To: /> Hosted by: Adept Scientific http://www.adeptscience.com List Archive: http://lists.adeptscience.co.uk/

RE: [MATHCAD] An amazing Plot, lost some points?
Author: Pergande, Albert N    Posted: Mon, 06 Sep 1999 13:34:57 -0400
I think the bug is the ability to plot without properly specifying a range variable. Like Implicit multiplication, it creates more problems than it solves. > -----Original Message----- > From: Ruben O. Domenech /> > Sent: Thursday, September 02, 1999 11:03 PM > To: /> > Cc: /> > Subject: Fw: [MATHCAD] An amazing Plot, lost some points? > > I think that you can get a clearer picture of what is happening if you > format both plots selecting some symbol (as x's) instead of none in the > 'traces' tag. > > By doing so, it looks like Mathcad has been using the following series of > omega values to calculate points of G: > > 1, 10^7, 2*10^7, 3*10^7, 4*10^7 ... in the first plot, and > 1, 10^5, 2*10^5, 3*10^5, 4*10^5 ... in the second one. > > I guess that Mathcad is trying to use 1000 points to give by default a > (supposedly) fair representation of the function, but... with very poor > fortune, because it uses points evenly spaced in a natural scale, while in > the plot is specified to use a logaritmic one. > > I believe this is indeed a bug in Mathcad, and that it deserves to be > fixed. > > ----- Original Message ----- > From: Pergande, Albert N /> > To: /> > Sent: 1 de septiembre de 1999 15:29 > Subject: RE: [MATHCAD] An amazing Plot, lost some points? > > > You haven't defined omega anywhere other than as the pass parameter to > functions A and G. In version 8, MathCAD takes a wild guess, usually 0 to > 10 > in steps of 0.1, when you plot a function without giving it a valid range > variable. I recommend you create a range variable i with the number of > points you want to plot, and make omega [ i a function of i and plot > against > it. Life will be much easier. > > -----Original Message----- > From: Peter Wehrli /> > Sent: Wednesday, September 01, 1999 9:17 AM > To: /> > Subject: [MATHCAD] An amazing Plot, lost some points? > > > Hello everybody, > > > The attached file "switcher.mcd" contains a Bode plot of simple first > order low pass filter (two resistor and a capacitor). > > Now I have the following Question: > > How it is possible, that plot depends on the x-range? that means if I > change the right End of the plotrange from 10E8 to 10E10, the frequency > respons in the plot at a frequency for example at about 10 E6 Hz is > almost 20dB wrong!!! > > It seams to me, that there are not enough points in the plot.Does exist > an option in Mathcad to fix that problem, or is it a nasty bug? > > Thank you for a good idea to solve this problem > > Peter Wehrli > Zühlke Engineering AG > CH-8952 Schlieren-Zürich > e-mail: /> > > > ------------------------------------------------------------- > The Mathcad List - Discussion, Support & News > Contributions: /> > To unsubscribe: Send in the body: unsubscribe mathcad > To: /> > Hosted by: Adept Scientific http://www.adeptscience.com > List Archive: http://lists.adeptscience.co.uk/ > > ------------------------------------------------------------- > The Mathcad List - Discussion, Support & News > Contributions: /> > To unsubscribe: Send in the body: unsubscribe mathcad > To: /> > Hosted by: Adept Scientific http://www.adeptscience.com > List Archive: http://lists.adeptscience.co.uk/ ------------------------------------------------------------- The Mathcad List - Discussion, Support & News Contributions: /> To unsubscribe: Send in the body: unsubscribe mathcad To: /> Hosted by: Adept Scientific http://www.adeptscience.com List Archive: http://lists.adeptscience.co.uk/

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