Peak value
in [Design]
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From: Tim Wescott on 2 Aug 2010 12:47 On 08/02/2010 08:59 AM, john1987 wrote: > On Aug 2, 11:44 am, Tim Wescott<t...(a)seemywebsite.com> wrote: >> On 08/02/2010 07:24 AM, john1987 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? >> >> Tons of them, but most are more complicated. Why don't you want to use >> an RC circuit? If it's complication, you're barking up the wrong tree. >> >>> 2. Whats the difference between in this case between using the High >>> pass and low pass filter? >> >> A low-pass filter will have a much less noisy output, but will really >> only find the peak for a repetitive sine wave over a narrow frequency >> range. A high-pass filter will, in theory, find the peak perfectly >> every time. In reality it'll be very noise sensitive and may well find >> lots and lots of "peaks" that you're not interested. >> >>> 3. How a PLL can help in this case? >> >> _If_ you're trying to sample the peaks of a repetitive wave at steady >> frequency, and _if_ it is symmetrical about the peaks, then a PLL will >> average out tons of noise. It satisfies the exceedingly vague "no RC >> circuit" requirement, but since you've never (that I've seen) elaborated >> on _why_ you don't want an RC circuit I have no idea if it'd be better >> or worse. >> >>> 4. Any advice about choosing the right ADC? >> >> You have given absolutely positively not enough information. I'd >> suggest starting another thread for that. >> >>> 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. >> >> Add in a noise source, and see how you like it. >> >> -- >> >> Tim Wescott >> Wescott Design Serviceshttp://www.wescottdesign.com >> >> Do you need to implement control loops in software? >> "Applied Control Theory for Embedded Systems" was written for you. >> See details athttp://www.wescottdesign.com/actfes/actfes.html- Hide quoted text - >> >> - Show quoted text - > > hi, > > what info you need to advice regarding choosing the ADC. I have > following info., > > 1. peak to peak voltage 2volts. > 2. frequency 100khz > 3 monotonic sine wave. Surely you care about accuracy? -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" was written for you. See details at http://www.wescottdesign.com/actfes/actfes.html
From: Jim Thompson on 2 Aug 2010 12:54 On Mon, 2 Aug 2010 08:30:40 -0700 (PDT), john1987 <conphiloso(a)hotmail.com> wrote: >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 > >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 You've either... (1) Messed up and didn't connect per my drawing. (2) Don't realize that U1 is a comparator. Post or send your PSpice files. ...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: Jim Thompson on 2 Aug 2010 12:57 On Mon, 2 Aug 2010 08:57:45 -0700 (PDT), john1987 <conphiloso(a)hotmail.com> wrote: >On Aug 2, 11:49�am, John Larkin ><jjlar...(a)highNOTlandTHIStechnologyPART.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 >> >> If, as I think, you are generating the sine wave, why do you need to >> derive its peak time from the signal itself? >> >> And if, as I think, you are intending to make an RLC meter, why do you >> want to measure the peak? >> >> John- Hide quoted text - >> >> - Show quoted text - > >Hi, > >I want to measure the peak because I want to control the peak to peak >sine wave amplitde using PWM. So, if the peak changes the micro will >use the PWM to control the voltage and keep it stable at the peak that >I mention in the diagram. > >John Crikey! See why we insist on definition of end function. Comparator with +1V reference. Use comparator output to pump-up/pump-down PWM control... whatever that might be ;-) ...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: Tim Wescott on 2 Aug 2010 13:27 On 08/02/2010 08:57 AM, john1987 wrote: > On Aug 2, 11:49 am, John Larkin > <jjlar...(a)highNOTlandTHIStechnologyPART.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 >> >> If, as I think, you are generating the sine wave, why do you need to >> derive its peak time from the signal itself? >> >> And if, as I think, you are intending to make an RLC meter, why do you >> want to measure the peak? >> >> John- Hide quoted text - >> >> - Show quoted text - > > Hi, > > I want to measure the peak because I want to control the peak to peak > sine wave amplitde using PWM. So, if the peak changes the micro will > use the PWM to control the voltage and keep it stable at the peak that > I mention in the diagram. If that's all you're doing, why not just use a precision rectifier? Search for it -- some semi company will have an app note about how to use one of their op-amps to make it all work. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" was written for you. See details at http://www.wescottdesign.com/actfes/actfes.html
From: Tim Wescott on 2 Aug 2010 13:28 On 08/02/2010 08:57 AM, john1987 wrote: > On Aug 2, 11:49 am, John Larkin > <jjlar...(a)highNOTlandTHIStechnologyPART.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 >> >> If, as I think, you are generating the sine wave, why do you need to >> derive its peak time from the signal itself? >> >> And if, as I think, you are intending to make an RLC meter, why do you >> want to measure the peak? >> >> John- Hide quoted text - >> >> - Show quoted text - > > Hi, > > I want to measure the peak because I want to control the peak to peak > sine wave amplitde using PWM. So, if the peak changes the micro will > use the PWM to control the voltage and keep it stable at the peak that > I mention in the diagram. Or, if you're doing this in a micro, just measure the sine wave at four arbitrary points in the waveform and calculate the mean squared value -- that'll be a constant no matter what the phase relationship is, as long as it stays a nice clean sine. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" was written for you. See details at http://www.wescottdesign.com/actfes/actfes.html
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