Biosensing &Signal Processing

Bio-sensing

In order to measure the flow-induced sounds inside the canonical phantom of the thorax, we will use commercially available cardiac sound devices such as the Hewlett Packard HP–21050A Contact Sensor and the BIOPAC TSD–108 Physiological Sounds Transducer (Contact Microphone). The HP Model 21050A Contact Sensor is designed to pick up heart sound and pulse wave signals for diagnostic references in biomedical studies. The 21050A Contact Sensor can be hand held or strapped to the phantom. It is important that the Contact Sensor housing be held firmly in place. This is especially true for low frequency sounds since the signal is the result of the displacement of the Contact sensor tip with respect to the housing. The BIOPAC TSD108 can record a variety of acoustical signals, including heart sounds and sounds associated with rubbing or grinding (e.g., Bruxism). The acoustical transducer element is similar to the HP-21050A in that it uses a piezo-electric ceramic disk, which is bonded to the interior of a circular metallic housing.

Specifications for the HP 21050A Contact Sensor are listed below.
Sensitivity : Force (10 uV/dyne), displacement (40mV/micron).
Frequency response : 0.02 Hz to 2000Hz, dependent upon the mechanical impedance of source and strapping to body.
Capacitance : 20nF.
Weight : Contact Sensor head (3.5oz/99gr), with accessories (8oz/227gr).
Size : Contact Sensor head (1.1in diameter and 1.14in thickness/28mm diameter and 29mm thickness).

Specifications for the BIOPAC TSD108 Contact Microphone are listed below.
Noise : 5 uV rms – (500 Hz – 3500 Hz).
Frequency response: 35 Hz to 3500 Hz.
Output : 2 V (p-p) maximum.

Weight : 9 g.

Size : 29mm diameter, 6mm thickness.