1. A conduit assembly for a fuel cell system, comprising:
a dielectric tube comprising a first end and a second end;
a first metal tube comprising a first lip coupled to the first end of the dielectric tube;
a first dielectric ring coupled to the first lip of the first metal tube;
a second metal tube comprising a second lip coupled to the second end of the dielectric tube; and
a second dielectric ring coupled to the second lip of the second metal tube.
2. The conduit assembly of claim 1, wherein the conduit assembly is incorporated into a fuel conduit of a fuel cell stack.
3. The conduit assembly of claim 2, wherein the dielectric tube and the first and second dielectric ring each comprise a ceramic.
4. The conduit assembly of claim of 3, wherein the ceramic comprises zirconia toughened alumina or silicon nitride.
5. The conduit of claim 3, wherein the dielectric tube and first and second dielectric rings have coefficients of thermal expansion that differ by 10\u22122 or less.
6. The conduit of claim 3, wherein the dielectric tube and first and second dielectric rings have coefficients of thermal expansion that differ by more than 10\u22122.
7. The conduit assembly of claim 2, wherein the first dielectric ring is located inside the first metal tube and the second dielectric ring is located inside the second metal tube.
8. The conduit assembly of claim 7, wherein the first lip extends inward from a circumference of the first metal tube and the second lip extends inward from a circumference of the second metal tube.
9. The conduit assembly of claim 2, wherein the first dielectric ring is located outside the first metal tube and the second dielectric ring is located outside the second metal tube.
10. The conduit assembly of claim 9, wherein the first lip extends outward from a circumference of the first metal tube and the second lip extends outward from a circumference of the second metal tube.
11. The conduit assembly of claim 2, wherein the first and second metal tubes comprise stainless steel or a nickel chromium alloy.
12. The conduit assembly of claim 2, wherein the first and second metal tubes are metal bellows.
13. The conduit assembly of claim 2, wherein the first and second metal tubes are coupled with metal bellows.
14. The conduit assembly of claim 13, wherein the first and second metal tubes are coupled with metal bellows by brazed or welded joints.
15. The conduit assembly of claim 2, wherein the dielectric tube and the first dielectric ring are coupled to the first lip by brazed joints, and wherein the dielectric tube and the second dielectric ring are coupled to the second lip by brazed joints.
16. The conduit assembly of claim 15, wherein the brazed joints comprise a nickel based braze alloy.
17. The conduit assembly of claim 2, wherein the first lip comprises a first surface coupled to the first end of the dielectric tube and a second surface opposite from the first surface and coupled to the first dielectric ring, and
wherein the second lip comprises a third surface coupled to the second end of the dielectric tube and a fourth surface opposite from the third surface and coupled to the second dielectric ring.
18. A fuel cell system, comprising:
a fuel cell stack comprising a fuel manifold;
and a fuel cell conduit assembly fluidly coupled to the fuel manifold, the fuel cell conduit assembly comprising:
a dielectric tube comprising a first end and a second end;
a first metal tube comprising a first lip coupled to the first end of the dielectric tube;
a first dielectric ring coupled to the first lip of the first metal tube;
a second metal tube comprising a second lip coupled to the second end of the dielectric tube; and
a second dielectric ring coupled to the second lip of the second metal tube.
19. A fuel cell system assembly method, comprising:
assembling a conduit assembly, comprising:
brazing or welding a first end of a dielectric tube to a first surface of a first lip of a first metal tube;
brazing or welding a first dielectric ring to a second surface of the first lip;
brazing or welding a second end of the dielectric tube to a third surface of a second lip of a second metal tube; and
brazing or welding a second dielectric ring to a fourth surface of the second lip; and
inserting the conduit assembly into the fuel cell system.
20. The method of claim 19, wherein inserting the conduit assembly into the fuel cell system comprises attaching the conduit assembly to a fuel manifold of a fuel cell stack, and wherein the dielectric tube and the first and second dielectric ring each comprise a ceramic.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method of detecting the presence of digitally modulated data signals, the method including differentially decoding the digitally modulated signals into oversampled complex signals comprising n samples per bit, forming a running sum of successive groups of m samples, where m is less than n, deriving an absolute value for the successive running sums, weighting the absolute value and determining the presence of data by comparing the weighted absolute value with a threshold level.
2. A method as claimed in claim 1, characterised in that the absolute value is weighted by comparing the absolute value with a plurality of threshold values of different magnitudes, the difference between threshold values of successive magnitudes comprising a window having a weighting value assigned to it, and in that the weighted absolute value is a product of the absolute value and a determined weighting value.
3. A method as claimed in claim 1 or 2, characterised by estimating the power level from the product of the absolute value and its associated weighting value.
4. A method as claimed in claim 1 or 2 wherein the digitally modulated signals comprise 2-FSK signals, characterised in that a constellation containing differentially decoded imaginary values is used to form the running sum.
5. A receiver comprising means for receiving a digitally modulated signal, means for forming the digitally modulated signal into an oversampled, differentially decoded complex signal comprising a stream of n samples per bit, means for forming a running sum of successive groups of m samples, where m is less than n, means for deriving an absolute value for successive running sums, weighting means for weighting the respective absolute values, and a comparator for comparing the weighted absolute value with a threshold level and providing an output indicative of the presence of data in the received signals.
6. A receiver as claimed in claim 5, characterised in that the weighting means comprises comparing means for comparing the derived absolute values with a plurality of threshold values and means for selecting a weighting value based on the result of the comparison, and in that multiplying means are provided for forming the weighted absolute value as a product of a respective absolute value and its associated weighting value.
7. A receiver as claimed in claim 5 or 6, characterised by a power level estimator coupled to an output of the multiplying means.
8. A receiver as claimed in claim 5 or 6, fabricated as an integrated circuit.
9. A telemetry module including a receiver as claimed in any one of claims 5 to 8.