Detecting the peak value
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From: John Fields on 30 Jul 2010 06:40 On Thu, 29 Jul 2010 14:26:31 -0700 (PDT), john1987 <conphiloso(a)hotmail.com> wrote: >Hi, > >+/- 10 % > >thanks >John --- Use Jim's circuit.
From: john1987 on 30 Jul 2010 10:28 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
From: John Larkin on 30 Jul 2010 10:34 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. What's wrong with an RC? Actually, and RC doesn't approach the required 90 degree lead or lag unless the time constant is huge, and then the signal is approaching zero. If your signal frequency is fairly steady, an R-L-C can do a lot better. Try this: in-------R------L---+------------comparator+ | | C | +------------comparator- | | gnd Pick the R-C to give, say, 70 degrees of lag at 100 KHz. Pick the L to add phase lag until the comparator switches just at the signal peaks, compensating for comparator delay while you're at it. R can be partly trimpot for fine tuning. This will preserve a healthy fraction of the original signal amplitude. I've also done this as in-------C----------+------------comparator+ | | R | L | small | offset---comparator- | | gnd as a fast constant-fraction discriminator, with an ecl comparator, instead of the usual delay-line thing. John
From: Jim Thompson on 30 Jul 2010 10:43 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 > > Then what's wrong with my suggestion... you don't like capacitors and want to spend more money ?:-) ...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: Richard Henry on 30 Jul 2010 10:43
On Jul 29, 10:17 am, john1987 <conphil...(a)hotmail.com> wrote: > Hi, > > I built the circuit that can detect the peak of the 100KHz , 2 Volts > peak to peak sine wave but its not accurate or may be not working > right. > The problems seem to be choosing the right R and C values. Is there > any way that I can do this with out using a Capcitor and a resistor > and if not than whats the best possible way to choose the R and C > values. > > I do require the edge to occur as close as possible to the sine wave > positive and negative peaks. > > I used Low Pass filter. you can find the diagram of the circuit and > the waveform at the following links. > > http://a.imageshack.us/img651/6509/161617.jpg > u > http://a.imageshack.us/img829/6505/161639.jpg > > Thanks > John You're not sampling fast enough. |