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dsPIC33EP256MC206: Internal Opamp CT interfacing

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karan123
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2019/12/25 23:06:06 (permalink)
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dsPIC33EP256MC206: Internal Opamp CT interfacing

 

Hi,

CT or Current Transformer with burden resistance
required Op-amp (s) for amplification.
Can I use Internal Op-amp(s) of dsPIC33EPxxx for Interfacing CT. I have to measure peak of sinusoidal signal (verying peak with frequency in KHz) which I have fed to ADC.

Actually I have monitor the (Inductive) load then set PWM Frequency and Duty cycle accordingly.

It's not energy measurement and metering application.

Any other suggestion (s)..with Internal or External High Speed Op-Amp are Welcome..

--
Karan
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5 Replies Related Threads

    ric
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    Re: dsPIC33EP256MC206: Internal Opamp CT interfacing 2019/12/25 23:08:43 (permalink)
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    Comes from https://www.microchip.com/forums/m1123090.aspx
    where some responses have already occurred, but does not answer the questions asked.

    I also post at: PicForum
    Links to useful PIC information: http://picforum.ric323.co...opic.php?f=59&t=15
    NEW USERS: Posting images, links and code - workaround for restrictions.
    To get a useful answer, always state which PIC you are using!
    #2
    NKurzman
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    Re: dsPIC33EP256MC206: Internal Opamp CT interfacing 2019/12/26 00:44:03 (permalink)
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    An op-amp may be required. It is not required in all designs. Carefully choosing the burden resistor may mean it’s not required.
    The internal Opamp could be used depending on the circuit details. But it’s not a great op amp.
    #3
    karan123
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    Re: dsPIC33EP256MC206: Internal Opamp CT interfacing 2019/12/26 00:53:43 (permalink)
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    Hi Thanks..
     
    Can you suggest me some High Speed Op-Amps,Op-Amp Topology ,App Notes to CT Interfacing ?
     
    --
    Karan
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    Mysil
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    Re: dsPIC33EP256MC206: Internal Opamp CT interfacing 2019/12/26 03:31:57 (permalink)
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    Hi,
    There is a long thread about interfacing with Current Transformer,
    with various frontend circuits suggested and discussed.
    Also code examples, although for PIC16 devices.
    https://www.microchip.com..ums/m845541.aspx#845541
     
    There is an external preamplifier circuit suggested in message
    It is not clear to me, wether you are mostly interested in Amplitude or Time of peak value.
    Identifying time of peak value in a possibly noisy signal, may be challenging, 
    and any filtering in hardware or software, is likely to shift the time of the peak.
     
    There is differential current to voltage frontend amplifier in message #30 and 42, 
    and several alternatives for precision rectifier circuits.
     
        Mysil
    post edited by Mysil - 2019/12/26 07:25:31
    #5
    du00000001
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    Re: dsPIC33EP256MC206: Internal Opamp CT interfacing 2019/12/26 03:36:17 (permalink)
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    @karan123
     
    https://www.analog.com/media/en/technical-documentation/application-notes/an105fa.pdf  (already given in the other thread) is a valuable resource. Fig. 61 does apply.
     
    To be honest: the questions you're asking are more those of a student than those of an engineer: you'd better ask an experienced analog designer to solve this particular problem (CT integration/adaptation) for you.
    BTW: the dsPIC's OpAmp should do as I don't expect too high frequencies in your application. Might require some low-pass filtering anyway to reduce noise.

    PEBKAC / EBKAC / POBCAK / PICNIC (eventually see en.wikipedia.org)
    #6
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