Data processing: measuring – calibrating – or testing – Measurement system – Measured signal processing
Reexamination Certificate
2002-06-28
2004-06-29
Barlow, John (Department: 2863)
Data processing: measuring, calibrating, or testing
Measurement system
Measured signal processing
C702S199000
Reexamination Certificate
active
06757641
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to transducers and in particular the present invention relates to determining a health state of transducers.
BACKGROUND OF THE INVENTION
A transducer is a device that provides an output signal calibrated to a monitored stimulus, such as temperature or pressure. The relationship between the output and the monitored stimulus is designed to remain relatively stable. As the transducer ages, however, the transducer ‘health’ changes and the input/output calibration may change.
There are many approaches to determine the health of a transducer. A healthy transducer is one that is reporting accurate output measurements. An unhealthy transducer is one that is either inoperable or reporting erroneous measurements not corresponding to the input stimulus it is receiving. Catastrophic failures of a transducer are obvious: either the sensor reports no value or it reports a value that is completely untenable. These cases are easily detected. The more subtle case to prevent is where the sensor drifts, or its calibration changes, and the user has no way to determine whether the sensor is bad or the stimulus has changed.
The canonical way to ensure a sensor's accuracy is to compare that sensor with another. It may possibly be compared to a “transfer standard” that is known to be very stable and agree well with other standards. Regardless, in comparing the questionable sensor with another, known to be healthy, the user can determine the health of the sensor. After determining the state of the sensor's health, then corrective action could be taken, such as repair or recalibration. Of course, this technique only works if at least one of the sensors is actually known to be accurate. When two arbitrary sensors are subjected to the same stimulus, if they report differing values it is unclear which is right and which is wrong.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for determining a health of one or more transducers.
SUMMARY OF THE INVENTION
The above-mentioned problems with transducers and other problems are addressed by the present invention and will be understood by reading and studying the following specification.
In one embodiment, a transducer comprises a plurality of sensors to provide a plurality of corresponding output signals in response to a stimulus, and a processor to apply a plurality of weight factors to each of the plurality of corresponding output signals and provide a single transducer output.
In another embodiment, a transducer comprises a plurality of sensors to provide a plurality of corresponding output signals in response to a stimulus, a memory to store a plurality of weight factors corresponding to the plurality of sensors, and a processor to apply a plurality of weight factors to each of the plurality of corresponding output signals and provide a single transducer output. A multiplex circuit selectively couples the plurality of corresponding output signals to the processor.
A method of providing an output from a multiple sensor transducer comprises sampling an output signal from each of the multiple sensors, and determining a weight factor for each sensor based upon the sampled output signals. The weight factor represents an accuracy level of the corresponding sensor. A single output signal is calculated by applying the weight factors to the sampled output signals. In one embodiment, the weight factors are calculated by the following algorithm,
(
W
i
)
-
1
=
1
2
N
∑
N
j
=
1
(
x
i
x
j
+
x
j
x
i
)
where N is the number of sensors, W
i
is the corresponding weight factor for sensor i providing output signal x
i
. The single output signal, Xoutput, can be calculated by the following algorithm,
X
output
=
∑
N
i
=
1
x
i
W
i
∑
N
j
=
1
W
j
.
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Horowitz and Hill, “The Art of Electronics”, 1989, Cambridge University Press, p. 635-636.
Eckhoff Anthony J.
Immer Christopher D.
Lane John
Perotti Jose M.
Barlow John
Borda Gary G.
Cherry Stephen J.
Heald Randall M.
Mannix John G.
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