Detecting the peak value
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From: Jim Thompson on 30 Jul 2010 12:52 On Fri, 30 Jul 2010 16:42:34 GMT, nico(a)puntnl.niks (Nico Coesel) wrote: >Jim Thompson <To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> >wrote: > >>On Thu, 29 Jul 2010 12:03:46 -0700 (PDT), john1987 >><conphiloso(a)hotmail.com> wrote: >> >>>I think that I am doing what are suggesting to use the differeniator. >>>But is there another analog way to do it meant without using the RC >>>circuit. >> >>You have an integrator (of sorts). >> >>I don't know of any way to find a sinusoid's peak without using a >>capacitor or a tracking A-to-D. >> >>This seems to work pretty well... >> >>http://analog-innovations.com/SED/PeakFinder_2.pdf >> >>"U1" is a comparator. > >Clever indeed. Are you working for Elektor these days? :-) I did a few magazine articles _many_ years ago. They don't pay well enough to even cover postage :-( It would be nice if the OP would "spill the beans" and let us know what he's really trying to accomplish. ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | Friday is Wine and Cheeseburger Day
From: john1987 on 30 Jul 2010 15:50 Hi, How should I select the vaues of capacitor and the resistor, if I go with the RC circuit. I have followin knowledge about it f= 1/ 2 pi RC F= 100KHz R= 10K C= 159 pF. Would it be the best way to go with? Will these values provide the edge right near the peak value of the sine wave? Thanks John
From: Jim Thompson on 30 Jul 2010 15:57 On Fri, 30 Jul 2010 12:50:32 -0700 (PDT), john1987 <conphiloso(a)hotmail.com> wrote: >Hi, >How should I select the vaues of capacitor and the resistor, if I go >with the RC circuit. I have followin knowledge about it > >f= 1/ 2 pi RC > >F= 100KHz > >R= 10K > >C= 159 pF. > >Would it be the best way to go with? Will these values provide the >edge right near the peak value of the sine wave? > >Thanks > >John Did you miss... Date: Thu, 29 Jul 2010 12:38:12 -0700 Message-ID: <c9l3569lk28o4r265qs5fntg8a04es50gm(a)4ax.com> [snip] This seems to work pretty well... http://analog-innovations.com/SED/PeakFinder_2.pdf "U1" is a comparator. Use 200pF and 82 Ohms per the schematic in the referenced PDF. ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | Spice is like a sports car... Performance only as good as the person behind the wheel.
From: John Fields on 30 Jul 2010 16:08 On Fri, 30 Jul 2010 07:28:22 -0700 (PDT), john1987 <conphiloso(a)hotmail.com> wrote: >Hi, > >The accuracy requirements are as follows > >1. The frequency of the sine wave is 100 kHz. +/- 3us --- Since 100kHz is 10 �s, 100kHz is 10�s +/- 3�s, (+/- 30% !!!) which means the period can vary from 10.3�s 9.7�s, which corresponds to frequencies of 67kHz and 133kHz, respectively. Since the period is 10�s and there are 360 degrees per cycle, that's 27.8ns per degree, so the +/- 3�s error would correspond to +/- 108 degrees. That's just insane, and it means that using simple phase shifting detectors won't work unless each one is individually tuned. --- >2 The amplitude is 2 volts peak to peak, it should be accurately >measured at +/- 1.9 volts. --- I don't understand what you mean by that. BTW, when you reply to a post leave enough of the post you're replying to in the reply so that someone will be able to figure out what you're talking about if they're just strating to read the thread with your reply. I notice you're posting through Google, so you might want to go by their guidelines: From: http://groups.google.com/support/bin/answer.py?answer=12348&topic=250 "Summarize what you're following up. When you click "Reply" under "show options" to follow up an existing article, Google Groups includes the full article in quotes, with the cursor at the top of the article. Tempting though it is to just start typing your message, please STOP and do two things first. Look at the quoted text and remove parts that are irrelevant. Then, go to the BOTTOM of the article and start typing there. Doing this makes it much easier for your readers to get through your post. They'll have a reminder of the relevant text before your comment, but won't have to re-read the entire article. And if your reply appears on a site before the original article does, they'll get the gist of what you're talking about." JF
From: Jim Thompson on 30 Jul 2010 16:51
On Fri, 30 Jul 2010 07:28:22 -0700 (PDT), john1987 <conphiloso(a)hotmail.com> wrote: >Hi, > >The accuracy requirements are as follows > >1. The frequency of the sine wave is 100 kHz. +/- 3us >2 The amplitude is 2 volts peak to peak, it should be accurately >measured at +/- 1.9 volts. >Its not a home work. :) > > >Thanks > >John > > Wheeeeee! � 1.9V is 3.8V Peak-to-Peak Your "signal" is only 2V Peak-to-Peak, or � 1V What is the REAL performance requirement/criteria? That is, what are you trying to accomplish when all is said and done? ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | Spice is like a sports car... Performance only as good as the person behind the wheel. |