Transducer construction and system for measuring respiration

Claim 2

A transducer assembly comprising: a moment-actuated transducer unit including a piezoelectric element having a predetermined capacitance, and a pair of bending arms affixed to and extending substantially perpendicular to said element; an elastic belt for supporting said unit, said belt being attached to said arms; fastener means for securing said belt at a predetermined tension about a selected portion of a subject''s body, said belt applying a moment to said arms according to its instantaneous tension whereby said element is actuated with expansion and contraction of said belt by said body portion to produce a variable electrical output signal from said element representative of the motions of said body portion; and a signal conditioning circuit having a high impedance input and a low impedance output, said output signal being applied to said high impedance input and said low impedance output being adapted to be connected to a recorder means, said conditioning circuit including means for adjusting its output reference base level to a predetermined value, and said reference base level adjusting means comprising sources of positive and negative voltages connected to supply said conditioning circuit in opposing polarities, and means connected to one of said sources and adjustable to adjust said reference base level to zero.

Claim 3

The invention as defined in claim 1 wherein said recorder means has a high input impedance, and said conditioning circuit further includes a filter means adapted to connect with said recorder means, said filter means comprising a low pass filter having a cut-off frequency of the order of about 0.2 hertz for eliminating the higher frequency and extraneous wavelets from the conditioned output signal applied to said recorder meaNs.

Claim 4

A transducer assembly comprising: a moment-actuated transducer unit including a piezoelectric element having a predetermined capacitance, and a pair of bending arms affixed to and extending substantially perpendicular to said element, said element comprising a deflectable beam and a piezoelectric crystal bonded to a surface of said beam, and said bending arms being affixed to said beam in a spaced relationship and extending a predetermined distance from said surface; an elastic belt for supporting said unit, said belt being attached to said arms; fastener means for securing said belt at a predetermined tension about a selected portion of a subject''s body, said belt applying a moment to said arms according to its instantaneous tension whereby said element is actuated with expansion and contraction of said belt by said body portion to produce a variable electrical output signal from said element representative of the motions of said body portion, said fastener means including complementary engaging layers of small barbs covering respective end sections of said belt, and said arms including a pair of loops affixed on one side to said beam in a spaced parallel relationship, the other side of said loops extending a predetermined distance freely from said surface and having said belt attached to the free sides of said loops whereby the moment applied to said arms by said belt deflects said beam and its bonded crystal to produce a related output signal from said element; and a signal conditioning circuit having a high impedance input and a low impedance output, said output signal being applied to said high impedance input and said low impedance output being adapted to be connected to a recorder means, said conditioning circuit including means for adjusting its output reference base level to a predetermined value and said conditioning circuit having an input impedance which provides in cooperation with said capacitance of said element, a predetermined time constant for regulating decay rate of said output signal.

Claim 5

A transducer assembly comprising: a moment-actuated transducer unit including a piezoelectric element having a predetermined capacitance, and a pair of bending arms affixed to and extending substantially perpendicular to said element, said element comprising a deflectable beam and a piezoelectric crystal bonded to a surface of said beam, and said bending arms being affixed to said beam in a spaced relationship and extending a predetermined distance from said surface; an elastic belt for supporting said unit, said belt being attached to said arms; fastener means for securing said belt at a predetermined tension about a selected portion of a subject''s body, said belt applying a moment to said arms according to its instantaneous tension whereby said element is actuated with expansion and contraction of said belt by said body portion to produce a variable electrical output signal from said element representative of the motions of said body portion, said fastener means including complementary engaging layers of small barbs covering respective end sections of said belt, and said arms including a pair of loops affixed on one side to said beam in a spaced parallel relationship, the other side of said loops extending a predetermined distance freely from said surface and having said belt attached to the free sides of said loops whereby the moment applied to said arms by said belt deflects said beam and its bonded crystal to produce a related output signal from said element; and a signal conditioning circuit having a high impedance input and a low impedance output, said output signal being applied to said high impedance input and said low impedance output being adapted to be connected to a recorder means, said conditioning circuit including means for adjusting its output reference base level to a predetermined value and said conditioning circuit having an input impedance which provides in cooperation with said capacitance of said element, a predetermined time constant for regulating decay rate of said output signal.

Claim 6

The invention as defined in claim 3 wherein said conditioning circuit includes an attenuator for preventing signal saturation in said recorder means, and said reference base level adjusting means comprises sources of positive and negative voltages connected to supply said conditioning circuit in opposing polarities, and means connected to one of said sources and adjustable to adjust said reference base level to zero.

Claim 7

The invention as defined in claim 4 wherein said attenuator comprises a series combination of a resistor of predetermined resistance and a Darlington impedance buffer stage, and said conditioning circuit further includes a filter means adapted to connect said attenuator to said recorder means, said filter means comprising a low pass filter for eliminating the higher frequency and extraneous wavelets from the conditioned output signal applied to said recorder means.

Claim 8

A transducer assembly comprising: a moment-actuated transducer unit including a piezoelectric element having a predetermined capacitance, and a pair of bending arms affixed to and extending substantially perpendicular to said element; an elastic belt for supporting said unit, said belt being attached to said arms; fastener means for securing said belt at a predetermined tension about a selected portion of a subject''s body, said belt applying a moment to said arms according to its instantaneous tension whereby said element is actuated with expansion and contraction of said belt by said body portion to produce a variable electrical output signal from said element representative of the motions of said body portion; and a signal conditioning circuit having a high impedance input and a low impedance output, said output signal being applied to said high impedance input and said low impedance output being adapted to be connected to a recorder means, said conditioning circuit including an attenuator for preventing signal saturation in said reCorder means, and said attenuator comprising a series combination of a resistor of predetermined resistance and a Darlington impedance buffer stage.

Claim 9

A transducer assembly comprising: a moment-actuated transducer unit including a piezoelectric element having a predetermined capacitance, and a pair of bending arms affixed to and extending substantially perpendicular to said element; an elastic belt for supporting said unit, said belt being attached to said arms; fastener means for securing said belt at a predetermined tension about a selected portion of a subject''s body, said belt applying a moment to said arms according to its instantaneous tension whereby said element is actuated with expansion and contraction of said belt by said body portion to produce a variable electrical output signal from said element representative of the motions of said body portion; and a signal conditioning circuit having a high impedance input and a low impedance output, said output signal being applied to said high impedance input and said low impedance output being adapted to be connected to a recorder means, said conditioning circuit including an attenuator for preventing signal saturation in said reCorder means, and said attenuator comprising a series combination of a resistor of predetermined resistance and a Darlington impedance buffer stage.

Claim 10

The invention as defined in claim 6 wherein said conditioning circuit has an input impedance which provides in cooperation with said capacitance of said element, a predetermined time constant for regulating decay rate of said output signal.