Quartz resonator pressure transducers and methods of operation
View Patent ↗A cylindrical quartz crystal transducer that exhibits a low probability of twinning, and uses a combination of resonator signal inputs at the B-mode and C-mode frequencies to calculate resonator temperature. Crystallographic orientations are disclosed where combinations of B-mode and C-mode resonant frequencies exist that are sufficiently independent of pressure to enable accurate calculation of temperature under transient conditions. Such a transducer is usable at higher pressures and temperatures than conventional quartz pressure transducers. Furthermore, because the structure allows a choice of crystallographic orientation, other characteristics of the transducer, such as increased pressure sensitivity and activity dip-free operation, may be optimized by varying crystallographic orientation.
1. A dual-mode pressure transducer, comprising:
a quartz crystal structure having a crystallographic orientation, wherein the quartz crystal structure comprises:
a double cut comprising:
a first cut having a first angular displacement (phi) about the X-axis of 26°; and
a second cut having a second angular displacement (theta) about the Z-axis between 33° and 34°;
a substantially cylindrical body having a longitudinal bore; and
a disc-shaped resonator carried by the body and extending transversely across the longitudinal bore; and
an electronics assembly in communication with the quartz crystal structure, the electronics assembly configured to:
drive the resonator;
receive signal inputs from the resonator from a non-fundamental B-mode resonant frequency primarily dependent on temperature;
receive other signal inputs from the resonator from a non-fundamental C-mode resonant frequency primarily dependent on pressure; and
calculate pressure-independent temperature under transient conditions using a combination of the signal inputs and the other signal inputs to compensate for the pressure determined from the non-fundamental C-mode resonant frequency.
2. The pressure transducer of claim 1 , wherein the disc-shaped resonator is integral with the body, and further including end caps secured to the body across opposing ends of the longitudinal bore.
3. The pressure transducer of claim 1 , wherein the body comprises first and second end caps, each end cap defining a portion of the longitudinal bore on opposing sides of the disc-shaped resonator and having the disc-shaped resonator secured therebetween.
4. The pressure transducer of claim 1 , wherein the resonator is a 3 rd overtone blank with a contour of 2.5 diopters on both sides.
5. A method of measuring a temperature-compensated pressure using a quartz crystal structure, the method comprising:
stimulating, under transient temperature conditions, the disc-shaped resonator of the quartz crystal structure of the dual-mode pressure transducer of claim 1 under external pressure applied to the quartz crystal structure to provide signal inputs from a non-fundamental B-mode resonant frequency and a non-fundamental C-mode resonant frequency; and
using a combination of the signal inputs to compensate a pressure determined from the non-fundamental C-mode resonant frequency signal input.
6. The method of claim 5 , wherein using a combination of the signal inputs comprises using a sum of the signal inputs.
7. The method of claim 5 , wherein the non-fundamental B-mode resonant frequency and the non-fundamental C-mode resonant frequency is the 3 rd harmonic of each mode.
8. The method of claim 5 , further comprising determining a change in temperature with the following equation:
Δ
T
=
(
f
C
+
Kf
B
-
f
C
1
-
Kf
B
1
)
(
f
C
1
C
T
+
Kf
B
1
B
T
)
.
9. The method of claim 5 , further comprising determining a change in pressure with the following equation:
Δ
P
=
C
T
C
P
(
f
C
1
C
P
+
Kf
B
1
B
P
)
(
f
C
1
C
T
+
Kf
B
1
B
T
)
H
.
10. The method of claim 9 , selecting a value of the constant K in the equation defining the change in pressure to minimize temperature dependence of the equation defining the change in pressure.
11. A dual-mode pressure transducer, comprising:
a quartz crystal structure comprising:
a resonator and having a crystallographic orientation; and
a substantially cylindrical body having a longitudinal bore, wherein the resonator is disc shaped, carried by the body and extends transversely across the longitudinal bore; and
an electronics assembly comprising at least one oscillator and at least one amplifier configured to drive the resonator, wherein the electronics assembly is in communication with the quartz crystal structure and is configured to provide signal inputs from the resonator comprising a non-fundamental B-mode resonant frequency primarily dependent on temperature and a non-fundamental C-mode resonant frequency of the resonator primarily dependent on pressure to enable calculation of temperature under transient conditions from a combination of the signal inputs.
12. The pressure transducer of claim 11 , wherein the disc-shaped resonator is integral with the body, and further including end caps secured to the body across opposing ends of the longitudinal bore.
13. The pressure transducer of claim 11 , wherein the body comprises first and second end caps, each end cap defining a portion of the longitudinal bore on opposing sides of the disc-shaped resonator and having the disc-shaped resonator secured therebetween.
14. The pressure transducer of claim 11 , wherein the non-fundamental resonant frequency of the B-mode and the non-fundamental resonant frequency of the C-mode is the 3 rd harmonic of each mode.
15. The pressure transducer of claim 11 , wherein the quartz crystal structure exhibits a crystallographic orientation with a first angular displacement (phi) about the X-axis between about 24° and less than about 30°.
16. The pressure transducer of claim 15 , wherein the first angular displacement (phi) about the X-axis is 26°.
17. The pressure transducer of claim 11 , wherein the crystallographic orientation comprises a second angular displacement (theta) about the Z-axis between about 33° and 34°.
18. The pressure transducer of claim 11 , wherein the quartz crystal structure enables the calculation of temperature of the resonator under transient conditions by employing f C +f B from the combination of the signal inputs for a first angular displacement (phi) about the X-axis angle of between 22° and 30°.
19. The pressure transducer of claim 11 , wherein the electronics assembly is further configured to calculate pressure-independent temperature under transient conditions using a combination of the signal inputs to compensate for the pressure determined from the non-fundamental C-mode resonant frequency.
20. The pressure transducer of claim 11 , wherein the electronics assembly is configured to calculate change in temperature and change in pressure with the following equations:
Δ
T
=
(
f
C
+
Kf
B
-
f
C
1
-
Kf
B
1
)
(
f
C
1
C
T
+
Kf
B
1
B
T
)
and
Δ
P
=
C
T
C
P
(
f
C
1
C
p
+
Kf
B
1
B
P
)
(
f
C
1
C
T
+
Kf
B
1
B
T
)
H
.
21. A dual-mode pressure transducer, comprising:
a quartz crystal structure having a crystallographic orientation with a first angular displacement (phi) about the X-axis greater than 24° and less than 30°, wherein the quartz crystal structure comprises:
a substantially cylindrical body having a longitudinal bore; and
a disc-shaped resonator carried by the body and extending transversely across the longitudinal bore; and
an electronics assembly in communication with the quartz crystal structure, the electronics assembly configured to:
drive the resonator; and
receive signal inputs from the resonator from a non-fundamental B-mode resonant frequency primarily dependent on temperature and from a non-fundamental C-mode resonant frequency primarily dependent on pressure to enable calculation of pressure-independent temperature of the resonator under transient conditions using the signal inputs.