Physiological sensor having reduced sensitivity to interference
View Patent ↗A physiological sensor having reduced sensitivity to interference includes a light source, a light detector in optical communication with the light source, and a sensor pad at least partially housing the light source and the light detector. The sensor pad is configured to be capacitively isolated from a patient. Moreover, the physiological sensor may be electrically connected to an amplifier having a signal ground and a monitor.
1. A sensor comprising:
a sensor pad;
a conductive material disposed on the sensor pad;
a printed circuit board disposed on the conductive material, the printed circuit board including a light source configured to generate light and a light detector configured to receive light generated by the light source,
wherein the sensor pad has a thickness that capacitively isolates the conductive material from a patient.
2. The sensor of claim 1 , wherein a capacitance of the conductive material relative to the patient is inversely proportional to a distance between the conductive material and the patient and the distance is based on the thickness of the sensor pad.
3. The sensor of claim 2 , wherein the capacitance between the conductive material and the patient is defined as: C p =∈ 0 ∈ r A/d, wherein C p is the capacitance in Farads, A is an area of the sensor pad disposed on the patient, d is a distance between the conductive material and the patient, ∈ r is a dielectric constant between the conductive material and the patient, and ∈ 0 is a permittivity of free space.
4. The sensor of claim 3 , wherein the dielectric constant between the conductive material and the patient is greater than 1.
5. The sensor of claim 1 , wherein the conductive material is electrically connected to the printed circuit board.
6. The sensor of claim 5 , wherein the conductive material and the printed circuit board are electrically grounded.
7. The sensor of claim 1 , wherein the printed circuit board includes traces configured to minimize an electromagnetic field generated between the traces.
8. The sensor of claim 1 , further comprising a light-blocking pad disposed on the sensor pad and configured to at least partially limit ambient light received by the light detector.
9. A system comprising:
an amplifier configured to receive signals representing physiological information, wherein the amplifier includes a monitor configured to graphically display the physiological information represented by the received signals; and
a sensor having a sensor pad, a conductive material disposed on the sensor pad, and a printed circuit board disposed on the conductive material, the printed circuit board including a light source configured to generate light and a light detector configured to receive light generated by the light source, wherein the sensor pad has a thickness that capacitively isolates the conductive material from a patient.
10. The system of claim 9 , wherein a capacitance of the conductive material relative to the patient is inversely proportional to a distance between the conductive material and the patient and the distance is based on the thickness of the sensor pad.
11. The system of claim 10 , wherein the capacitance between the conductive material and the patient is defined as: C p =∈ 0 ∈ r , A/d, wherein C p is the capacitance in Farads, A is an area of the sensor pad disposed on the patient, d is a distance between the conductive material and the patient, ∈ r is a dielectric constant between the conductive material and the patient, and ∈ 0 is a permittivity of free space.
12. The system of claim 9 , wherein the sensor pad is capacitively isolated from the monitor.
13. The system of claim 9 , wherein the conductive material is electrically connected to the printed circuit board.
14. The system of claim 13 , wherein the conductive material and the printed circuit board are electrically grounded.
15. The system of claim 9 , wherein the printed circuit board includes traces configured to minimize an electromagnetic field generated between the traces.
16. The system of claim 9 , wherein the sensor includes a light-blocking pad disposed on the sensor pad, wherein the light-blocking pad is configured to at least partially limit ambient light received by the light detector.
17. The system of claim 9 , further comprising a shield electrically disposed between the sensor and the amplifier.
18. The system of claim 9 , wherein the amplifier includes a signal ground electrically connected to the sensor and capacitively isolated from the monitor.
19. A sensor comprising:
a sensor pad;
a conductive material disposed on the sensor pad;
a printed circuit board disposed on the conductive material, the printed circuit board including a light source configured to generate light and a light detector configured to receive light generated by the light source,
wherein the sensor pad has a thickness that capacitively isolates the conductive material from a patient and wherein a distance between the conductive material and the patient is based on the thickness of the sensor pad, and
wherein a capacitance of the conductive material relative to the patient is defined as: C p =∈ 0 ∈ r , A/d, wherein C p is the capacitance in Farads, A is an area of the sensor pad disposed on the patient, d is a distance between the conductive material and the patient, ∈ r is a dielectric constant between the conductive material and the patient, and ∈ 0 is a permittivity of free space.