Capacitive pressure sensor
Pressure sensors and their methods of use are described. In one embodiment, a pressure sensor may include: a tubular probe body; a capacitive sensor disposed at the distal end of the probe body; a lead electrically coupled to the sensor extending along an interior space of the probe body; and at least one support formed of a material having a relatively low dielectric constant disposed within the probe body to support the lead and space the lead away from an inner wall of the probe body. This may help to minimize shunt capacitance and changes in shunt capacitance due to radial movement of the lead. In other embodiments, a pressure sensor may include a channel formed in a wall of the probe body, a temperature sensor disposed at a distal end of the probe body, and a temperature sensor lead disposed in the channel and connected to the temperature sensor.
1. A pressure sensor, comprising:
a tubular probe body having a proximal end and a distal end;
a capacitive sensor disposed at the distal end of the probe body;
a lead electrically coupled to the capacitive sensor and extending along an interior space of the tubular probe body toward the proximal end; and
at least one support formed of a material having a relatively low dielectric constant and disposed within the tubular probe body, the at least one support constructed and arranged to support the lead within the tubular probe body and space the lead away from an inner wall of the tubular probe body.
2. The pressure sensor according to claim 1 , wherein the at least one support comprises a material having a relatively low thermal coefficient of dielectric constant.
3. The pressure sensor according to claim 1 , wherein the at least one support comprises a material having a relatively low coefficient of thermal expansion.
4. The pressure sensor according to claim 1 , wherein the at least one support comprises a material selected from the group consisting essentially of quartz, ceramic and fused silica.
5. The pressure sensor according to claim 1 , wherein the at least one support comprises a disc-shaped component having an outer circumference engaging the inner wall of the tubular probe body and a hole through which the lead wire passes and is supported.
6. The pressure sensor according to claim 1 , wherein the at least one support supports the lead substantially concentrically within the tubular probe body.
7. The pressure sensor according to claim 1 , wherein the lead comprises a wire conductor.
8. The pressure sensor according to claim 1 , wherein the lead comprises a rod or tubular conductor.
9. The pressure sensor according to claim 1 , wherein the lead is shielded.
10. The pressure sensor according to claim 6 , wherein an annular air gap is provided between the lead and the inner wall of the tubular probe body.
11. The pressure sensor according to claim 1 , wherein an air gap is provided between the lead and the inner wall of the tubular probe body.
12. The pressure sensor according to claim 1 , wherein the at least one support comprises a plurality of supports intermittently spaced along the tubular probe body.
13. The pressure sensor according to claim 1 , wherein the intermittently spaced supports are constructed and arranged to minimize deflection of the lead and increase natural frequencies of lateral vibrations of the lead.
14. The pressure sensor according to claim 1 , wherein the tubular probe body includes a channel formed in a wall of the tubular probe body and extending from the distal end to the proximal end, and wherein the pressure sensor further comprises a temperature sensor disposed at the distal end of the tubular probe body, wherein a temperature sensor lead is disposed in the channel and connected to the temperature sensor.
15. The pressure sensor according to claim 14 , wherein the channel comprises one of a groove and a bore.
16. The pressure sensor according to claim 14 , wherein the temperature sensor comprises a thermocouple.
17. The pressure sensor according to claim 15 , further comprising a temperature sensor securing tube disposed in the tubular probe body to retain the temperature sensor lead in the groove.
18. The pressure sensor according to claim 17 , wherein the temperature sensor securing tube is press fit in the tubular probe body.
19. A pressure sensor, comprising:
a tubular probe body having a proximal end and a distal end, the tubular probe body includes a channel formed in a wall of the tubular probe body and extending from the distal end to the proximal end;
a capacitive sensor disposed at the distal end of the probe body;
a lead electrically coupled to the capacitive sensor and extending along an interior space of the tubular probe body toward the proximal end; and
a temperature sensor disposed at the distal end of the tubular probe body, wherein a temperature sensor lead is disposed in the channel and connected to the temperature sensor.
20. The pressure sensor according to claim 19 , wherein the channel comprises one of a groove and a bore.
21. The pressure sensor according to claim 19 , wherein the temperature sensor comprises a thermocouple.
22. The pressure sensor according to claim 20 , further comprising a temperature sensor lead tube disposed in the tubular probe body to retain the temperature sensor lead in the groove.
23. The pressure sensor according to claim 22 , wherein the temperature sensor lead tube is press fit in the tubular probe body.