PSN-L Email List Message

Subject: Re: amplifier noise
From: Bob Smither bob@...........
Date: Sat, 06 Jul 2013 16:43:23 -0500

On 07/06/2013 01:04 PM, JAMES RIDOUT wrote:
> Hello all, Sorry to be a pain, But ive just built the two 741 opamp circuits,
> Ive been very carefull with construction, but in getting a lot of noise!, if I
> unplug the feed from the coil im getting the data value (in amaseis), jumping
> about 1000 points +&-.
> im using two 12v switch mode power supplies.
>   Im not great at electronics, but I know the basics.
> Im using a dataq 194.
>   Any help would be great!.
>      Thanks,   James

Hi James,

The 741 is not considered a low noise amplifier.  Take a look at the Linear Tech
LT1007, for example.

It would help determine if what you are seeing is expected if we knew:

  circuit diagram (do you have link?)
  brand / model of power supply (switch mode is often pretty noisy)

The Dataq 194 is only 10 bits (counts of -512 to +512) so not sure I understand
the +/- 1000 counts observed.  Maybe something from Amaseis (I don't use that)?

Bob Smither                                 bob@...........
"Personality is the supreme realization of the innate
 idiosyncrasy of a living being.  It is an act of high
 courage flung in the face of life, the absolute
 affirmation of all that constitutes the individual, the
 most successful adaptation to the universal conditions of
 existence coupled with the greatest possible freedom for
  --C.G. Jung

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