Pressure measurement artifact with analog-to-digital conversion.

Pressure was transduced with the use of a fluid-filled catheter and standard medical monitoring equipment. When the signal was sampled at 200 Hz with an analog-to-digital converter, an artifact was observed. The 3.5-Hz artifact had an amplitude of 0.3 to 0.9 mm Hg and was caused by aliasing of a noise contaminant from the 2,403.5-Hz electrical excitation signal of the transducer. The artifact was completely eliminated with a 100-Hz low-pass filter. Electrical filtering is necessary for accurate acquisition of pressure measurements with analog-to-digital conversion, even when the sampling rate satisfies the Nyquist criterion for the frequency response of the mechanical system. Although the impact of the artifact is small in the clinical area, it is important under some research circumstances.