NI DAQ 6210 Arterial Waveform and Waveform Graph

[EngineeringEE]

Hi All,

I am using a USB DAQ 6210 to take differential measurements from a pressure sensor placed over the radial artery.  I am trying to detect the arterial waveform for blood pressure and heart rate estimation.  FIG2 is where my problem happens.  The waveform looks like what you see in the FIG2 attachment like a signal with drift on it.  I have done all I can with noise cancellation on my circuit.  The circuit sits inside of a Faraday cage.

The sensor is powered by a AA battery pack which is hooked up to a voltage regulator.  I used a power supply to see if it was drift from using batteries but I still get the same result.  It is a half bridge gauge sensor which is completed with two 800 OHM resistors.  The output of the sensor is buffered and amplified by an instrumentation amplifier where the output is read by the 6210. I need to get a steady and clear signal with minimal fluctuations.  I was wondering if this is a problem with the DAQ?  Has anyone seen something similar happen when using a pressure sensor and DAQ? I need to get rid of this drifting in my signal.

[Henrik_Volkers]

Try a 2.order IIR high-pass filter with 0,2 Hz.

(or .5 or 1 or ?? Hz)

Or, since you have build the hardware: add a high-pass filter (or DC / drift cut)  between your amp and the DAQ. 

[EngineeringEE]

I am running a 2 HZ low pass filter.  The signal is usually within 2.5 HZ range.  I figured it out though.  I see the drift when the signal is not "strong" enough.  I adjusted my gain and the drift went away.