Noninvasive blood flow sensor using magnetic field parallel to skin
First Claim
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1. An apparatus for noninvasive measurement of blood flow, comprising:
- A probe incorporating two varying magnetic field poles of opposite polarity mounted near the bottom surface of said probe so that when said probe is placed adjacent to the skin there is a component of varying magnetic flux extending beneath and parallel to said skin;
An electrical field sense electrode mounted on the bottom of said probe between said opposite polarity varying magnetic field poles so that when said probe is placed adjacent to said skin said electrical field sense electrode is in contact with or capacitively coupled to said skin;
An electrical field reference electrode placed in contact with or capacitively coupled to said skin and removed from the area of varying magnetic flux generated by said varying magnetic field poles; and
Synchronous detection electric circuitry which samples the voltage difference between said electrical field sense electrode and said electrical field reference electrode at two or more times during each cycle of said varying magnetic field, and provides an output voltage related to the variation of said voltage difference corresponding to said varying magnetic field.
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Abstract
An improved electromagnetic blood flow sensor uses a bipolar magnetic field source to provide a varying magnetic field with a component parallel to the skin and through the blood vessel, a single sense electrode on the skin adjacent to the blood vessel, a reference electrode, and a detector that samples the sense electrode signal in synchronism to the varying magnetic field. An optional addition is a driven shield for the sense electrode to reduce the effect of noise voltages either from the magnetic field source or from stray fields.
149 Citations
11 Claims
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1. An apparatus for noninvasive measurement of blood flow, comprising:
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A probe incorporating two varying magnetic field poles of opposite polarity mounted near the bottom surface of said probe so that when said probe is placed adjacent to the skin there is a component of varying magnetic flux extending beneath and parallel to said skin; An electrical field sense electrode mounted on the bottom of said probe between said opposite polarity varying magnetic field poles so that when said probe is placed adjacent to said skin said electrical field sense electrode is in contact with or capacitively coupled to said skin; An electrical field reference electrode placed in contact with or capacitively coupled to said skin and removed from the area of varying magnetic flux generated by said varying magnetic field poles; and Synchronous detection electric circuitry which samples the voltage difference between said electrical field sense electrode and said electrical field reference electrode at two or more times during each cycle of said varying magnetic field, and provides an output voltage related to the variation of said voltage difference corresponding to said varying magnetic field. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification