AVR-Chat

I wonder if someone could help me with some advice please. I am trying
to use an AVR microcontroller to monitor an analogue signal. The
signal is both very low and of high impedance, so initially I wish to
experiment a little by using a general purpose amplifier between the
source and the AVR. I have found a HP 465A or a Brookdeal 9452 for not
too much cash. Does anyone have any experience with either instrument,
the HP has fixed gains of 20db or 40db while the Brookdeal is
apparently variable 30-100db so either has suitable gain.
Thanks for your time.
Doug Locke.

Doug Locke wrote:
> I wonder if someone could help me with some advice please. I am trying
> to use an AVR microcontroller to monitor an analogue signal. The
> signal is both very low and of high impedance, so initially I wish to
> experiment a little by using a general purpose amplifier between the
> source and the AVR. I have found a HP 465A or a Brookdeal 9452 for not
> too much cash. Does anyone have any experience with either instrument,
> the HP has fixed gains of 20db or 40db while the Brookdeal is
> apparently variable 30-100db so either has suitable gain.
> Thanks for your time.
> Doug Locke.

An important thing to specify is the signal bandwidth, or what the source
of the signal is. If you're "monitoring" the signal with a digital input,
you just need a comparator and simple RC filter. For an ADC input, an opamp
amplifier and some RFI filtering will do.

Thanks Russell
Anything with a bandwidth up to say a Mhz would be fine for this. I was
rather thinking along the lines of obtaining something general where I had
no need to worry about design for now and that would also be an asset for
future work. Once I have established the feasability and best approach is
the time to look at a specific input circuit.

Regards.
Doug.

  -----Original Message-----
  From: AVR-Chat@yahoogroups.com [mailto:AVR-Chat@yahoogroups.com]On Behalf
Of Russell Shaw
  Sent: 16 August 2006 01:52
  To: AVR-Chat@yahoogroups.com
  Subject: Re: [AVR-Chat] General purpose amplifier to use with AVR


  Doug Locke wrote:
  > I wonder if someone could help me with some advice please. I am trying
  > to use an AVR microcontroller to monitor an analogue signal. The
  > signal is both very low and of high impedance, so initially I wish to
  > experiment a little by using a general purpose amplifier between the
  > source and the AVR. I have found a HP 465A or a Brookdeal 9452 for not
  > too much cash. Does anyone have any experience with either instrument,
  > the HP has fixed gains of 20db or 40db while the Brookdeal is
  > apparently variable 30-100db so either has suitable gain.
  > Thanks for your time.
  > Doug Locke.

  An important thing to specify is the signal bandwidth, or what the source
  of the signal is. If you're "monitoring" the signal with a digital input,
  you just need a comparator and simple RC filter. For an ADC input, an
opamp
  amplifier and some RFI filtering will do.


  


[Non-text portions of this message have been removed]

--- In AVR-Chat@yahoogroups.com, "Doug Locke" <doug@...> wrote:
>
> I wonder if someone could help me with some advice please. I am trying
> to use an AVR microcontroller to monitor an analogue signal. The
> signal is both very low and of high impedance, so initially I wish to
> experiment a little by using a general purpose amplifier between the
> source and the AVR. I have found a HP 465A or a Brookdeal 9452 for not
> too much cash. Does anyone have any experience with either instrument,
> the HP has fixed gains of 20db or 40db while the Brookdeal is
> apparently variable 30-100db so either has suitable gain.
> Thanks for your time.
> Doug Locke.


My ancient 465 'scope has a output on the rear for the A-channel
amplifier, which I have used from time to time for just the purpose
you mention.  It is a very nice feature, and I think some other
'scopes have it as well.

On 8/16/06, Doug Locke <doug@whiteapple.u-net.com> wrote:
>
> Thanks Russell
> Anything with a bandwidth up to say a Mhz would be fine for this. I was
> rather thinking along the lines of obtaining something general where I had
> no need to worry about design for now and that would also be an asset for
> future work. Once I have established the feasability and best approach is
> the time to look at a specific input circuit.


The AVR ADC can't do anything near that bandwidth.
100kHz would be plenty, unless you have some unusual requirements.
Op-amp on a breadboard sort of thing.


[Non-text portions of this message have been removed]

I think that the amplifiers from Texas Instruments can do what you want ,they have a very big collection of amps of different bandwidths...for more info see digikey catalog

Doug Locke <doug@whiteapple.u-net.com> wrote:        Thanks Russell
Anything with a bandwidth up to say a Mhz would be fine for this. I was
rather thinking along the lines of obtaining something general where I had
no need to worry about design for now and that would also be an asset for
future work. Once I have established the feasability and best approach is
the time to look at a specific input circuit.

Regards.
Doug.

-----Original Message-----
From: AVR-Chat@yahoogroups.com [mailto:AVR-Chat@yahoogroups.com]On Behalf
Of Russell Shaw
Sent: 16 August 2006 01:52
To: AVR-Chat@yahoogroups.com
Subject: Re: [AVR-Chat] General purpose amplifier to use with AVR

Doug Locke wrote:
> I wonder if someone could help me with some advice please. I am trying
> to use an AVR microcontroller to monitor an analogue signal. The
> signal is both very low and of high impedance, so initially I wish to
> experiment a little by using a general purpose amplifier between the
> source and the AVR. I have found a HP 465A or a Brookdeal 9452 for not
> too much cash. Does anyone have any experience with either instrument,
> the HP has fixed gains of 20db or 40db while the Brookdeal is
> apparently variable 30-100db so either has suitable gain.
> Thanks for your time.
> Doug Locke.

An important thing to specify is the signal bandwidth, or what the source
of the signal is. If you're "monitoring" the signal with a digital input,
you just need a comparator and simple RC filter. For an ADC input, an
opamp
amplifier and some RFI filtering will do.

[Non-text portions of this message have been removed]



         



 		
---------------------------------
Do you Yahoo!?
 Get on board. You're invited to try the new Yahoo! Mail Beta.

[Non-text portions of this message have been removed]

That was a nice little function they began putting in their tube type 
scopes back in the 300/500 series days and have carried forward to their 
current models.  Makes a really nice buffer amplifier.  7000 series can 
be had for a song these days but be careful that you buy one that works 
because the knobs aren't even available any more.

And please be gentle when you speak of "ancient" things.  I cut my teeth 
on the 545s and 585s back when they were current catalog items...12AX7 
tubes...6AU6s, 12AT7s, 6922s...tuned delay lines.  Still have 2 copies 
of the RCA receiving tube manual that aren't opened very often so as not 
to lose any pages.  Then there were nuvistors...


REB


erikc77099 wrote:

>--- In AVR-Chat@yahoogroups.com, "Doug Locke" <doug@...> wrote:
>  
>
>>I wonder if someone could help me with some advice please. I am trying
>>to use an AVR microcontroller to monitor an analogue signal. The
>>signal is both very low and of high impedance, so initially I wish to
>>experiment a little by using a general purpose amplifier between the
>>source and the AVR. I have found a HP 465A or a Brookdeal 9452 for not
>>too much cash. Does anyone have any experience with either instrument,
>>the HP has fixed gains of 20db or 40db while the Brookdeal is
>>apparently variable 30-100db so either has suitable gain.
>>Thanks for your time.
>>Doug Locke.
>>    
>>
>
>
>My ancient 465 'scope has a output on the rear for the A-channel
>amplifier, which I have used from time to time for just the purpose
>you mention.  It is a very nice feature, and I think some other
>'scopes have it as well.
>
>  
>


[Non-text portions of this message have been removed]

Doug Locke wrote:
>   -----Original Message-----
>   From: AVR-Chat@yahoogroups.com [mailto:AVR-Chat@yahoogroups.com]On Behalf
> Of Russell Shaw
>   Sent: 16 August 2006 01:52
>   To: AVR-Chat@yahoogroups.com
>   Subject: Re: [AVR-Chat] General purpose amplifier to use with AVR
> 
> 
>   Doug Locke wrote:
>   > I wonder if someone could help me with some advice please. I am trying
>   > to use an AVR microcontroller to monitor an analogue signal. The
>   > signal is both very low and of high impedance, so initially I wish to
>   > experiment a little by using a general purpose amplifier between the
>   > source and the AVR. I have found a HP 465A or a Brookdeal 9452 for not
>   > too much cash. Does anyone have any experience with either instrument,
>   > the HP has fixed gains of 20db or 40db while the Brookdeal is
>   > apparently variable 30-100db so either has suitable gain.
>   > Thanks for your time.
>   > Doug Locke.
> 
>   An important thing to specify is the signal bandwidth, or what the source
>   of the signal is. If you're "monitoring" the signal with a digital input,
>   you just need a comparator and simple RC filter. For an ADC input, an
> opamp
>   amplifier and some RFI filtering will do.
 >
 > Thanks Russell
 > Anything with a bandwidth up to say a Mhz would be fine for this. I was
 > rather thinking along the lines of obtaining something general where I had
 > no need to worry about design for now and that would also be an asset for
 > future work. Once I have established the feasability and best approach is
 > the time to look at a specific input circuit.

Hi,
1MHz is quite high for software actions to cope with, other than interrupt-
driven pulse counting. For the ADC, i'd suggest using 1MHz GBW opamps to make
x10 amps with 100kHz BW, or x100 amps with 10kHz BW.