Peak value
in [Design]
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From: john1987 on 2 Aug 2010 10:24 Hi, I think my question got buried in the discussion so I am putting my question out there again. Please be patient. I am attaching two new drawings to show what I want. I do not know about accuracy but i would as say as much as accurate as possible. First link is as follows http://img828.imageshack.us/i/scan0001j.jpg/ Second link is as follows http://img299.imageshack.us/i/scan0002db.jpg/ I want to sample the peak value of the sine wave by using ADC (sampling rate 200ksps). I want to sample the peak value of the sine wave at the rising edge or the falling edge of the square wave that you can see in the diagram. The edges will trigger the ADC and ADC will sample that edge. The ADC can not sample the negative values as shown in the diagram. I did not mention the circuitry that can add offset to the input signal and make it all positive. The questions are 1. Is there any way other than RC circuit to get the peak sample of the sine wave at the rising and falling edge? 2. Whats the difference between in this case between using the High pass and low pass filter? 3. How a PLL can help in this case? 4. Any advice about choosing the right ADC? 5. I tested the suggested high pass filter using the 220pF and 7.6kOhm resistor and found that the edge is occuring at the right spot in pspice than the low pass filter. Thanks John
From: Michael Kellett on 2 Aug 2010 11:02 "john1987" <conphiloso(a)hotmail.com> wrote in message news:6885cfb2-9af0-4f8f-b041-af665e672f9c(a)l25g2000prn.googlegroups.com... > Hi, > I think my question got buried in the discussion so I am putting my > question out there again. Please be patient. > > I am attaching two new drawings to show what I want. I do not know > about accuracy but i would as say as much as accurate as possible. > > > First link is as follows > http://img828.imageshack.us/i/scan0001j.jpg/ > > > Second link is as follows > > > http://img299.imageshack.us/i/scan0002db.jpg/ > > > I want to sample the peak value of the sine wave by using ADC > (sampling rate 200ksps). I want to sample the peak value of the sine > wave at the rising edge or the falling edge of the square wave that > you can see in the diagram. The edges will trigger the ADC and ADC > will sample that edge. The ADC can not sample the negative values as > shown in the diagram. I did not mention the circuitry that can add > offset to the input signal and make it all positive. > > > The questions are > > > 1. Is there any way other than RC circuit to get the peak sample of > the sine wave at the rising and falling edge? > 2. Whats the difference between in this case between using the High > pass and low pass filter? > 3. How a PLL can help in this case? > 4. Any advice about choosing the right ADC? > 5. I tested the suggested high pass filter using the 220pF and > 7.6kOhm > resistor and found that the edge is occuring at the right spot in > pspice than the low pass filter. > > > Thanks > John > > I think that at last I understand what you are trying to do but you need to answer some more questions before I could offer any solution. How much does the frequency of the '200kHz' sine wave vary How much does the amplitude vary and how fast How pure is the 200kHz sine wave - ie how much 400kHz, 600kHz etc Do you need to catch every single positve and negative peak or would every 16th (or 8th or 32nd) one be OK Michael Kellett
From: Jim Thompson on 2 Aug 2010 11:04 On Mon, 2 Aug 2010 07:24:24 -0700 (PDT), john1987 <conphiloso(a)hotmail.com> wrote: >Hi, >I think my question got buried in the discussion so I am putting my >question out there again. Please be patient. > >I am attaching two new drawings to show what I want. I do not know >about accuracy but i would as say as much as accurate as possible. > > >First link is as follows >http://img828.imageshack.us/i/scan0001j.jpg/ > > >Second link is as follows > > >http://img299.imageshack.us/i/scan0002db.jpg/ > > >I want to sample the peak value of the sine wave by using ADC >(sampling rate 200ksps). I want to sample the peak value of the sine >wave at the rising edge or the falling edge of the square wave that >you can see in the diagram. The edges will trigger the ADC and ADC >will sample that edge. The ADC can not sample the negative values as >shown in the diagram. I did not mention the circuitry that can add >offset to the input signal and make it all positive. > > >The questions are > > >1. Is there any way other than RC circuit to get the peak sample of >the sine wave at the rising and falling edge? >2. Whats the difference between in this case between using the High >pass and low pass filter? >3. How a PLL can help in this case? >4. Any advice about choosing the right ADC? >5. I tested the suggested high pass filter using the 220pF and >7.6kOhm >resistor and found that the edge is occuring at the right spot in >pspice than the low pass filter. > > >Thanks >John > All of your questions have been previously answered. What is eluding you? The suggested "hi-pass" is actually a differentiator and 7.6K should be 75 to 82 Ohms, NOT K! ...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: john1987 on 2 Aug 2010 11:26 On Aug 2, 11:02 am, "Michael Kellett" <nos...(a)nospam.com> wrote: > "john1987" <conphil...(a)hotmail.com> wrote in message > > news:6885cfb2-9af0-4f8f-b041-af665e672f9c(a)l25g2000prn.googlegroups.com... > > > > > > > Hi, > > I think my question got buried in the discussion so I am putting my > > question out there again. Please be patient. > > > I am attaching two new drawings to show what I want. I do not know > > about accuracy but i would as say as much as accurate as possible. > > > First link is as follows > >http://img828.imageshack.us/i/scan0001j.jpg/ > > > Second link is as follows > > >http://img299.imageshack.us/i/scan0002db.jpg/ > > > I want to sample the peak value of the sine wave by using ADC > > (sampling rate 200ksps). I want to sample the peak value of the sine > > wave at the rising edge or the falling edge of the square wave that > > you can see in the diagram. The edges will trigger the ADC and ADC > > will sample that edge. The ADC can not sample the negative values as > > shown in the diagram. I did not mention the circuitry that can add > > offset to the input signal and make it all positive. > > > The questions are > > > 1. Is there any way other than RC circuit to get the peak sample of > > the sine wave at the rising and falling edge? > > 2. Whats the difference between in this case between using the High > > pass and low pass filter? > > 3. How a PLL can help in this case? > > 4. Any advice about choosing the right ADC? > > 5. I tested the suggested high pass filter using the 220pF and > > 7.6kOhm > > resistor and found that the edge is occuring at the right spot in > > pspice than the low pass filter. > > > Thanks > > John > > I think that at last I understand what you are trying to do but you need to > answer some more questions before I could offer any solution. > > How much does the frequency of the '200kHz' sine wave vary > How much does the amplitude vary and how fast > How pure is the 200kHz sine wave - ie how much 400kHz, 600kHz etc > Do you need to catch every single positve and negative peak or would every > 16th (or 8th or 32nd) one be OK > > Michael Kellett- Hide quoted text - > > - Show quoted text - Hi, The frequency of the sine wave will stay 100KHz (10usec). I do not know exactly how much will it be varying but I guess we can design for the error of +/- 0.001usec from its original value. I do not know how much the amplitude be varying, I would say +/- 0.0001 volts. How fast , I do not know. You can assume some realistic value. If you advice how to design the system around these values than later I will take the error values into account when I get the true values later. It is pure 100KHz sine wave. I do need to catch every single positive and negative peak. Thanks john
From: john1987 on 2 Aug 2010 11:30 On Aug 2, 11:04 am, Jim Thompson <To-Email-Use-The-Envelope-I...(a)On-My- Web-Site.com> wrote: > On Mon, 2 Aug 2010 07:24:24 -0700 (PDT), john1987 > > > > > > <conphil...(a)hotmail.com> wrote: > >Hi, > >I think my question got buried in the discussion so I am putting my > >question out there again. Please be patient. > > >I am attaching two new drawings to show what I want. I do not know > >about accuracy but i would as say as much as accurate as possible. > > >First link is as follows > >http://img828.imageshack.us/i/scan0001j.jpg/ > > >Second link is as follows > > >http://img299.imageshack.us/i/scan0002db.jpg/ > > >I want to sample the peak value of the sine wave by using ADC > >(sampling rate 200ksps). I want to sample the peak value of the sine > >wave at the rising edge or the falling edge of the square wave that > >you can see in the diagram. The edges will trigger the ADC and ADC > >will sample that edge. The ADC can not sample the negative values as > >shown in the diagram. I did not mention the circuitry that can add > >offset to the input signal and make it all positive. > > >The questions are > > >1. Is there any way other than RC circuit to get the peak sample of > >the sine wave at the rising and falling edge? > >2. Whats the difference between in this case between using the High > >pass and low pass filter? > >3. How a PLL can help in this case? > >4. Any advice about choosing the right ADC? > >5. I tested the suggested high pass filter using the 220pF and > >7.6kOhm > >resistor and found that the edge is occuring at the right spot in > >pspice than the low pass filter. > > >Thanks > >John > > All of your questions have been previously answered. > > What is eluding you? > > The suggested "hi-pass" is actually a differentiator and 7.6K should > be 75 to 82 Ohms, NOT K! > > ...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)460-2350begin_of_the_skype_highlighting (480)460-2350 end_of_the_skype_highlighting Fax: Available upon request | Brass Rat | > | E-mail Icon athttp://www.analog-innovations.com| 1962 | > > Spice is like a sports car... > Performance only as good as the person behind the wheel.- Hide quoted text - > > - Show quoted text - Hi, I tried the circuit with your values in pspice and found that the circuit is not detecting the peak positive and neagtive sine values at the rising and falling edge of the square wave. So, I played with the R and C values and found the 220pF and 7.6kohm got the edges right where I wanted. But I sitll do not know that its a good solution. Any advice on choosing the ADC too. Thanks John
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