help with op-amp circuit - pci6221 and bnc2111, problems with multiple channels

[sensorimotor_nsc]

Hello,

I'm trying to record force values from 4 pressure sensors, using the PCI 6221 card and BNC 2111 connector box. I put together an amplifying circuit that works off of 2x9V batteries, a TL082CP op amp chip and a circuit in a biopolar supply arrangement. This worked with one pressure sensor at a time, but there is obviously a problem in cross-talk between the op-amp chips because when i hook up my battery power leads to each chip, only one works.

Instead of troubleshooting the existing circuit, does anyone have suggestions for a simple 4 channel amplifier circuit that will work with the DAQ hardware I have? The force sensors that I'm using are the flexiforce line of sensors from Tekscan.

Thanks in advance for the help.

Brian

[Brandon_B]

Hello Brian,

I'm not really sure what the output range of your pressure sensors are, but the PCI-6221 has four selectable input ranges.  Most pressure sensors have a maximum output in the low mV range, so what you could do is use the +/- 200mV range on your card in order to obtain the best resolution from your signal.  This will allow you to detect changes in voltage at a step of 6.4uV.  I hope this helps.

Regards,