The Low Frequency Velocity Measurement Ballistocardiograph

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Abstract
The velocity measurement ballistocardiograph is described which has filter circuits to eliminate body tremor components. Small adjustable condensers are utilized on the input and output of the filter section to vary the frequency response of the circuit and thus create a sharper cut-off for occasional cases with high amplitude body tremor. The input and output condenser values are not above 5 mfd. in either section. By utilizing this type of circuitry, the lack of wave distortion makes it feasible to measure the ratios of wave amplitudes. The timing device makes it practical to time wave segments from the peak of the R wave, and a single channel recorder can be utilized. Normal standards are described and deviations from normal in coronary artery disease are discussed. The low frequency, velocity measurement ballistocardiograph is easily adaptable for routine office use.