• Audio Attenuator

    From Chris M. White@21:1/5 to All on Tue Jun 8 21:29:47 2021
    Hi guys,

    I have an old vintage HP audio osciallator which I want to use for
    some experimentation to get more practice in electronics. Its output
    is continually variable between 4 and 20 volts. Problem is, for some experiments I have in mind, I need it to output only between 1mV and
    10mV. The oscailator's output impedance is 600 ohms it states.
    Can anyone suggest a simple passive attenuator I could build from
    easily available components which would give me this much lower output
    please?
    thanks!

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  • From Phil Hobbs@21:1/5 to Chris M. White on Wed Jun 9 04:06:44 2021
    Chris M. White wrote:
    Hi guys,

    I have an old vintage HP audio osciallator which I want to use for
    some experimentation to get more practice in electronics. Its output
    is continually variable between 4 and 20 volts. Problem is, for some experiments I have in mind, I need it to output only between 1mV and
    10mV. The oscailator's output impedance is 600 ohms it states.
    Can anyone suggest a simple passive attenuator I could build from
    easily available components which would give me this much lower output please?
    thanks!


    A bit more detail would be useful.

    However, something like a resistive voltage divider will probably be a
    good place to start.


    10k
    GEN 0----RRRRR----*----0 OUT
    |
    R
    R 10 ohms
    R
    |
    |
    GND

    To get down to 1 mV, you can hang a pot on the output. Figuring out
    just how to do that would be a step forward.

    Cheers

    Phil Hobbs

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  • From Jasen Betts@21:1/5 to White on Wed Jun 9 08:10:12 2021
    On 2021-06-08, Chris M White <cw9877@gsm.com> wrote:
    Hi guys,

    I have an old vintage HP audio osciallator which I want to use for
    some experimentation to get more practice in electronics. Its output
    is continually variable between 4 and 20 volts. Problem is, for some experiments I have in mind, I need it to output only between 1mV and
    10mV. The oscailator's output impedance is 600 ohms it states.
    Can anyone suggest a simple passive attenuator I could build from
    easily available components which would give me this much lower output please?
    thanks!

    a simple resistive divider will give a fixed ratio reduction in
    amplitude, unfortunately that won't cover the whole 10:1 range you
    want as your input only has 5:1 adjustment.

    You could use a potentiometer to make an adjustable attenuator and get
    a variable reduction that way.


    --
    Jasen.

    --- SoupGate-Win32 v1.05
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  • From Phil Hobbs@21:1/5 to Chris M. White on Wed Jun 9 11:37:00 2021
    On 6/9/21 11:24 AM, Chris M. White wrote:
    On Wed, 9 Jun 2021 04:06:44 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Chris M. White wrote:
    Hi guys,

    I have an old vintage HP audio osciallator which I want to use for
    some experimentation to get more practice in electronics. Its output
    is continually variable between 4 and 20 volts. Problem is, for some
    experiments I have in mind, I need it to output only between 1mV and
    10mV. The oscailator's output impedance is 600 ohms it states.
    Can anyone suggest a simple passive attenuator I could build from
    easily available components which would give me this much lower output
    please?
    thanks!


    A bit more detail would be useful.

    I'm happy to oblige. Anything specific?

    What's the load? Any DC involved?


    However, something like a resistive voltage divider will probably be a
    good place to start.


    10k
    GEN 0----RRRRR----*----0 OUT
    |
    R
    R 10 ohms
    R
    |
    |
    GND

    To get down to 1 mV, you can hang a pot on the output. Figuring out
    just how to do that would be a step forward.

    What's the problem in that? Seems simple enough to my simple mind!


    Well, if you understand pots, you understand voltage dividers already.

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    https://hobbs-eo.com

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  • From Chris M. White@21:1/5 to pcdhSpamMeSenseless@electrooptical. on Wed Jun 9 16:24:04 2021
    On Wed, 9 Jun 2021 04:06:44 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Chris M. White wrote:
    Hi guys,

    I have an old vintage HP audio osciallator which I want to use for
    some experimentation to get more practice in electronics. Its output
    is continually variable between 4 and 20 volts. Problem is, for some
    experiments I have in mind, I need it to output only between 1mV and
    10mV. The oscailator's output impedance is 600 ohms it states.
    Can anyone suggest a simple passive attenuator I could build from
    easily available components which would give me this much lower output
    please?
    thanks!


    A bit more detail would be useful.

    I'm happy to oblige. Anything specific?


    However, something like a resistive voltage divider will probably be a
    good place to start.


    10k
    GEN 0----RRRRR----*----0 OUT
    |
    R
    R 10 ohms
    R
    |
    |
    GND

    To get down to 1 mV, you can hang a pot on the output. Figuring out
    just how to do that would be a step forward.

    What's the problem in that? Seems simple enough to my simple mind!

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Allison@21:1/5 to Chris M. White on Wed Jun 9 17:24:00 2021
    Chris M. White wrote:
    -----------------------------

    A bit more detail would be useful.
    I'm happy to oblige. Anything specific?

    ** What old HP have you got?

    Sure it has not been modified to get only 4-20V out ?
    Seems weird otherwise.


    ..... Phil

    --- SoupGate-Win32 v1.05
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  • From Chris M. White@21:1/5 to pcdhSpamMeSenseless@electrooptical. on Thu Jun 10 22:34:49 2021
    On Wed, 9 Jun 2021 11:37:00 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    On 6/9/21 11:24 AM, Chris M. White wrote:
    On Wed, 9 Jun 2021 04:06:44 -0400, Phil Hobbs
    <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Chris M. White wrote:
    Hi guys,

    I have an old vintage HP audio osciallator which I want to use for
    some experimentation to get more practice in electronics. Its output
    is continually variable between 4 and 20 volts. Problem is, for some
    experiments I have in mind, I need it to output only between 1mV and
    10mV. The oscailator's output impedance is 600 ohms it states.
    Can anyone suggest a simple passive attenuator I could build from
    easily available components which would give me this much lower output >>>> please?
    thanks!


    A bit more detail would be useful.

    I'm happy to oblige. Anything specific?

    What's the load? Any DC involved?

    No DC and very high impedance load (> 1M ohm)




    However, something like a resistive voltage divider will probably be a
    good place to start.


    10k
    GEN 0----RRRRR----*----0 OUT
    |
    R
    R 10 ohms
    R
    |
    |
    GND

    To get down to 1 mV, you can hang a pot on the output. Figuring out
    just how to do that would be a step forward.

    What's the problem in that? Seems simple enough to my simple mind!


    Well, if you understand pots, you understand voltage dividers already.

    My main concern was not to draw too much from the already quite high
    impedance (600 ohms) of the source generator. Did you allow for that
    in the values you came up with?

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