Data processing: measuring – calibrating – or testing – Calibration or correction system – Sensor or transducer
Reexamination Certificate
2002-05-29
2003-12-23
Barlow, John (Department: 2863)
Data processing: measuring, calibrating, or testing
Calibration or correction system
Sensor or transducer
Reexamination Certificate
active
06668236
ABSTRACT:
BACKGROUND OF THE INVENTION.
The process is of a type comprising a system (transducer) which converts a value of an angular displacement into a different quantity, in the example an electrical signal representing the indication of the displacement measured. A problem common to all transducers is the linearization of the measurement in output with those measured so that a required degree of accuracy is obtained.
In more general terms, the problem is finding a practical way to determine and enact a correlation between input measurement (the angle to be measured) and output measurement, which represents with the required level of exactness the “true”relation (never strictly linear) between the two within a certain field of definition i.e. the field of use of the sensor.
Usual methods mostly utilise calibration systems based on the reading of a few pairs of measurements (generally two or three) with which a relation between input measurement and output measurement is constructed, in geometrical terms, from a curve described by the pairs. This is the cause of errors of linearization which tend to increase progressively for pairs of measurements having pair values which are increasingly different to those used for the construction of the correlation (curve).
The use of a large number of pair values, however, for constructing the curve would lead to considerable complication in calculation, without guaranteeing an improvement in the approximation.
The main aim of the present invention is to obviate the drawbacks and limits in the prior art.
This aim and more besides are all attained by the present invention as it is characterised in the accompanying claims.
SUMMARY OF THE INVENTION
A process for calibrating a sensor for measuring an angle of inclination of a motor vehicle wheel, comprising a transducer which converts a unit of measurement of an angular displacement into a different quantity, constituted in the example by an electrical signal, which represents an indication of the measured angle, comprising: reading a plurality of known measurements relating to known and different angular displacements x
j
; reading and storing a plurality of ordered pairs (x
j
, f
j
), where x
j
=known measurement of angular displacement and f
j
=corresponding measurement of a transduced quantity obtained from a reading; calculation of a plurality of low-degree interpolating polynomials which are lower than the plurality of ordered pairs (x
j
, f
j
), each of which results from a determined number of the ordered pairs of contiguous ordered pairs (x
j
, f
j
). A calculation of a measurement of an angular displacement not coinciding with any of known measurements for angular displacements x
j
is performed with at least one polynomial interpolation using at least one of the interpolating polynomials, which is selected so that a measurement f read at the sensor for measurement x of the angular displacement (to be measured) is comprised within a field described by measurements f
j
belonging to contiguous ordered pairs (x
j
, f
j
).
REFERENCES:
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patent: 6195606 (2001-02-01), Barta et al.
patent: 6327785 (2001-12-01), Dale, Jr. et al.
patent: 6341013 (2002-01-01), Battiti et al.
patent: 6446018 (2002-09-01), Isermann et al.
patent: 6480778 (2002-11-01), Tanak et al.
patent: 2002/0166389 (2002-11-01), Desbiolles
Barlow John
Browdy and Neimark , P.L.L.C.
Pretlow Demetrius
Snap-on Equipment S.r.l.
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