Detecting the peak value
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From: john1987 on 30 Jul 2010 17:07 Hi, 200pF and 82 ohm resistor gives me approximately 9 Mhz frequency and its a high pass filter. SO, does it mean that filter will pass all the frequncies less than 9MHz. Thanks John
From: Jim Thompson on 30 Jul 2010 17:16 On Fri, 30 Jul 2010 14:07:46 -0700 (PDT), john1987 <conphiloso(a)hotmail.com> wrote: >Hi, > >200pF and 82 ohm resistor gives me approximately 9 Mhz frequency and >its a high pass filter. SO, does it mean that filter will pass all the >frequncies less than 9MHz. > > >Thanks >John Stop snipping content and look at my drawing. ...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 30 Jul 2010 17:28 On Jul 30, 5:16 pm, Jim Thompson <To-Email-Use-The-Envelope-I...(a)On-My- Web-Site.com> wrote: > On Fri, 30 Jul 2010 14:07:46 -0700 (PDT), john1987 > > <conphil...(a)hotmail.com> wrote: > >Hi, > > >200pF and 82 ohm resistor gives me approximately 9 Mhz frequency and > >its a high pass filter. SO, does it mean that filter will pass all the > >frequncies less than 9MHz. > > >Thanks > >John > > Stop snipping content and look at my drawing. > > ...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. Hi, I looked at your drawing and also simulated in pspice. Why did you go for the High pass filter? I tried 220pF and 7.6KOhm. Is HPF more accurate than LPF? The positive peak voltage is + 1 volts and negative peak voltage is - 1 volts. So, 2 volts peak to peak. I do not know how accurate should be the measured voltage. It would be desirable to have it as little as possible. when said and done, I will read the voltage into the ADC and read the numbers and try to monitor the voltage across the resistor. Thanks John
From: Jim Thompson on 30 Jul 2010 18:41 On Fri, 30 Jul 2010 14:28:46 -0700 (PDT), john1987 <conphiloso(a)hotmail.com> wrote: >On Jul 30, 5:16�pm, Jim Thompson <To-Email-Use-The-Envelope-I...(a)On-My- >Web-Site.com> wrote: >> On Fri, 30 Jul 2010 14:07:46 -0700 (PDT), john1987 >> >> <conphil...(a)hotmail.com> wrote: >> >Hi, >> >> >200pF and 82 ohm resistor gives me approximately 9 Mhz frequency and >> >its a high pass filter. SO, does it mean that filter will pass all the >> >frequncies less than 9MHz. >> >> >Thanks >> >John >> >> Stop snipping content and look at my drawing. >> >> � � � � � � � � � � � � � � � � � � � � ...Jim Thompson [snip] > >Hi, > >I looked at your drawing and also simulated in pspice. Why did you go >for the High pass filter? I tried 220pF and 7.6KOhm. Is HPF more >accurate than LPF? Why did you try 7.6K Ohm when I said 82 Ohms? It's a differentiator, so you place it much higher in frequency than the signal. > >The positive peak voltage is + 1 volts and negative peak voltage is - >1 volts. So, 2 volts peak to peak. > >I do not know how accurate should be the measured voltage. It would be >desirable to have it as little as possible. Doesn't matter for differentiator. We're looking for sign change (slope, at the input peak) with the comparator. > >when said and done, I will read the voltage into the ADC and read the >numbers and try to monitor the voltage across the resistor. > >Thanks > >John You said you wanted a transition... as you drew it. Do you want the peak voltage? What is it you want? ...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: Grant on 30 Jul 2010 19:47
On Fri, 30 Jul 2010 16:38:57 GMT, nico(a)puntnl.niks (Nico Coesel) wrote: >Grant <omg(a)grrr.id.au> wrote: > >>On Thu, 29 Jul 2010 12:01:20 -0700 (PDT), john1987 <conphiloso(a)hotmail.com> wrote: >> >>> >>> >>>Hi, >>>Thanks for your response. I need analog or digital solution to >>>implement it. I have doe search on peak detector on the internet and >>>found many circuits. But I need something that can do what I mentioned >>>in the diagram. Ideally with out those capacitor and resistor. If you >>>can direct me in correct way than I wil be thankful. >> >>Also see my post in reply to Jim T. >> >>You can do it in software, but not easily for 100kHz. That's >>need DSP techniques, I think? > >Nope. Just do random time sampling using a simple microcontroller. As >long as the S&H can handle 100kHz it's fine. Keep in mind that today's >microcontrollers are 32 bit, run at >50MHz and have hardware >multipliers and dividers. Erm, in my mind, a microcontroller is smaller, like a PIC chip, I really do have difficulty realising the ARMs and other 32bit controllers are about as cheap and have so much greater power :) But then I time-travel in a sense from early '90s, returning to electronics after a long break. And, picking up where I left off, in a sense, by using the PIC chips. That'll do for this year, for me. Grant. |