Opamp noise

I'm not sure if this is the correct place to ask this, but here goes.
I have build an opamp ciruit to amplify the signal from a force
transducer. This is working fine, but the problem that I am having is
that if someone walks around it different spots, my steady state level
will change by almost 50mV or sometimes more. I have removed the
transducer and shorted the diff inputs of the opamp to ground through
a resister and I get the same effect. I have grounded the gnd 0V rail
to earth along with the transducer as well. I have used caps near the
opamp but still no luck. I have a Tektronix TDS2014 for which I am
analyzing the signal and if I touch the probe wire, the output level
of the opamp will go up 20 or 30 millivolts. These are brand new
scope probes and I have tried four of them, they all do the same
thing, so I am ruling them out.

Is there a way that I can elliminate this. I need to get acturate
reading into my process, but whenever someone moves, this level moves
up and interferes with the signal. I am using a TI INA126
Differiential op amp with a gain of 1000.

I have even tried placing the entire circuit inside a grounded wire
screen cage and I still get the same effect. I also know that it is
not vibration being transmitted to the transducer because of the above
forementioned removal of transducer and replacing with resister to
ground.

Thanks,

James
.

Relevant Pages

  • Re: Opamp noise
    ... I have build an opamp ciruit to amplify the signal from a force ... transducer and shorted the diff inputs of the opamp to ground through ... detector for RF signals. ... Filtering on the front end will elliminate my DC gain. ...
    (comp.arch.embedded)
  • Re: Opamp noise
    ... I have build an opamp ciruit to amplify the signal from a force ... transducer and shorted the diff inputs of the opamp to ground through ... detector for RF signals. ... Filtering on the front end will elliminate my DC gain. ...
    (comp.arch.embedded)
  • Re: Opamp noise
    ... I have build an opamp ciruit to amplify the signal from a force ... transducer and shorted the diff inputs of the opamp to ground through ... detector for RF signals. ... Filtering on the front end will elliminate my DC gain. ...
    (comp.arch.embedded)
  • Re: Opamp noise
    ... I have build an opamp ciruit to amplify the signal from a force ... transducer and shorted the diff inputs of the opamp to ground through ... Do you have your 'scope set to BW limit? ... detector for RF signals. ...
    (comp.arch.embedded)
  • Re: Opamp noise
    ... I have build an opamp ciruit to amplify the signal from a force ... transducer and shorted the diff inputs of the opamp to ground through ... analyzing the signal and if I touch the probe wire, ... There is a circuit on this datatsheet as well as an explaination as to ...
    (comp.arch.embedded)