Coded data generation or conversion – Converter compensation
Reexamination Certificate
1998-12-15
2001-08-21
JeanPierre, Peguy (Department: 2819)
Coded data generation or conversion
Converter compensation
C341S155000
Reexamination Certificate
active
06278389
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a sensor arrangement comprising two sensors and a processing circuit, having two A/D converter units each receiving a sensor signal from one of the sensors to an angular-position sensor arrangement comprising two angular-position sensors which are angularly spaced from one another and a similar processing unit, and to a method of measurement-error detection for such a sensor arrangement.
Such a sensor arrangement is known from the Philips Data Handbook SC 17, Semiconductor Sensors, 1997, pages 186-187. In said arrangement two angular-position sensors are each connected to an A/D converter unit (A/D=analog/digital). The angular-position sensors, which each comprise four measuring elements in a bridge arrangement, are spaced at an angle of 45° from one another and each produce a sinusoidal sensor signal on the output. As a result of the angularly spaced arrangement these sensor signals are 90° phase-shifted. By means of a processing unit a measurement signal is determined, which is for example proportional to the angular position of a measurement object relative to the sensor arrangement.
It has been found that on the input of the processing unit, particularly during the A/D conversion of the sensor signals, errors can occur which invalidate the measurement signal to be determined without this being detectable from the measurement signal or the sensor signals in the known sensor arrangement. Such errors can be caused, for example, by a faulty A/D converter unit. Moreover, the sensors themselves may operate incorrectly.
BRIEF SUMMARY OF THE INVENTION
It is an object of the invention to take simple measures in order to detect such errors in the known sensor arrangement.
According to the invention this object is achieved by means of the sensor arrangement having two sensors connected through a switch to respective A/D converter units. In said arrangement, as in the known arrangement, a first measurement signal is calculated in a first switching state. However, in a second switching state the connections between the sensors and the A/D converter units are interchanged, so that each A/D converter unit receives the other sensor signal. In this switching state a second measurement signal is determined, which is then compared with the first measurement signal. This comparison yields an error signal which indicates whether an error occurs or not. The error criterion can then be, for example, the difference between the two measurement signals, for which a limit value can be defined. This effective solution for the detection of errors at the input of the processing unit is very cheap and in the simplest case it requires the provision of simple switching means between the two sensors and the two A/D converter units. Such switching means can be, for example, simple clock-pulse controlled switches or a multiplexer.
In a preferred embodiment, a memory stores the sensor signals processed in the first switching state, and furnishes them to the A/D units in the second switching state. This guarantees that the sensor signals processed by the A/D converter units in the second switching state do not differ from the sensor signals processed in the first switching state. Such memory means must be provided, for example, when the measurement quantity, for example the angular position of a measurement object, changes very rapidly. Conversely, when it can be guaranteed that the sensor signals do not change in the first and the second switching state, said memory means may be dispensed with.
In another embodiment, to enable errors in the processing unit to be detected as well, a second arithmetic unit is used in addition to the one arithmetic unit provided in the known sensor arrangement. It is possible, for example, to determine the first measurement signal by means of the first arithmetic unit and the second measurement signal by means of the second arithmetic unit in order to thereby detect errors in the arithmetic unit. It is also conceivable to first determine a first and a second measurement signal by means of the first arithmetic unit and then in a second step to determine again a first and a second measurement signal by means of the second arithmetic unit (from the same sensor signals as in the calculation by means of the first arithmetic unit) and subsequently to compare these.
Moreover, in a further embodiment, the sensor arrangement can be extended with a further sensor pair which is identical to the first sensor pair and whose sensor signals are processed in a third and a fourth switching state as a redundancy for the first sensor pair. This requires only a minor modification of the processing unit. The operation of the sensor arrangement is then sustained even in the event of failure of one sensor or a complete sensor pair.
The invention is particularly suitable for use in an angular-position sensor arrangement. The measurement-error detection method broadly covering all the above embodiments can also be used in any other sensor arrangement in which a measurement signal is derived from two sensor signals.
REFERENCES:
patent: 4937443 (1990-06-01), Smoot
patent: 5012124 (1991-04-01), Hollaway
Philips Data Handbook SC17, Semiconductors Sensors, 1997, pp. 186-187.
Lochmann Hans-Ulrich
Pusch Stefan
Jean-Pierre Peguy
U.S. Philips Corporation
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