gettin rid of a voltage offset

[biomedeng110]

Hi Guys

any ideas on how to get rid of a dc offset, im using two pressure transducers, and want to find the difference in pressure over the two sensor, but at atmospheric pressure im getting a dirty offset of about 2 volts at both pressure sensors, and i need it to be at zero, i cant use a high pass filter because it will cut out some of my signal
any ideas?

 

[IRstuff]

AC coupling is one approach.

A manual adjustment DAC generating a comparable DC offset is another

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[Skogsgurra]

The offset seems to be identical on the two transducers. So they cancel if you take the difference - which you want to do anyroads. I do not quite understand what the problem is.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[biomedeng110]

hi thanks for your replies

yeah i realized i just need to use a instrumentation amplifier to get common mode rejection, which gets rid of the offset being at 2v, but now its at 100mV and i need to amplify the signal, so i still need to get rid of 100mV offset

@ Skogsgurra, the two pressure sensors are places either side of a resistive film, and when air is blown into them, they will produce different pressures, then therefore work out the difference of pressure over the resistive film

mind my ignorance but is there a op amp which you could subtract voltage from the other input? so say i amplified this by gain of 10, my offset would now be 1v, could i some how subtract 1v?

 

[VEBill]

This sounds like the sort of situation where the first step should be a bridge circuit[/LINK]. If the two pressure transducers are two-wire sensors (neither side grounded), as is most likely, then it should be a very simple approach to wire them up such that they cancel-out anything that they have in common.

If there's a residual offset, then you would have to calibrate that out using an analog or digital offset.


Another totally different approach would be to use a two-port pressure difference sensor and plumb it so that it directly measures the delta.

 

[IRstuff]

" op amp which you could subtract voltage from the other input?"

that would pretty much describe every op amp ever built. You need to read up or get some help.

Is this for a school project?

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize