US 4,907,175 AGranted

Monitoring device

AssigneeU.S. Philips Corporation

InventorsAntonius W. C. M. Van Alphen, Erwin Hogeweg

Life of this patent

Estimating the term…

Loading patent…

Abstract

A monitoring device comprises a transmitter and a receiver for transmitting and receiving, respectively, a signal in a medium to be monitored. During a cycle of m sampling periods n sampling values are taken of the signal received during each sampling period. After completion of each cycle a series of n means sampling values is determined by determining a mean value from the m sampling values taken at corresponding instants in the sampling periods. This series forms an actual pattern word which is sub-divided into sub-pattern words, each sub-pattern word being combined with a corresponding sub-pattern word from a reference pattern word in order to form a combination word. The combination word is translated into a code number which is selected from a predetermined series of code numbers. The code number assigned characterizes the time shift of the actual sub-pattern word with respect to the reference pattern word. For each cycle there is determined a series of sum numbers which represent how many times each code number has been assigned. This series of sum numbers is tested with respect to a criterion. If one or more sum numbers of the series exceeds the limit value given, a signal is generated, for example an alarm signal.

Claims38

Dependent claims

A monitoring device, comprising a central unit means whereto there are connected a transmitter for periodically transmitting a pulse train into a medium to be monitored and a receiver for receiving the pulse train which is transported by the medium and which is formed by a wave group, which central unit means comprises a control member for controlling a monitoring device and a sampling unit which is connected to the receiver for taking in correlation with the transmission of the pulse train and each time within a sampling cycle, a series of n sampling values from the wave group received, where n is greater than 3 and for forming an actual pattern word from said series, which control member is connected to a signal generator and comprises a reference memory for storing a reference pattern word formed during a preceding cycle, which control member also comprises a control unit which is connected to the reference memory and which comprises a comparator, characterized in that the control unit also sub-divides the period of the wave group received into a further number of n/j sub-periods, where j is greater than 1, and sub-divides the actual pattern word and the reference pattern word into n/j j-bit first sub-pattern words and second sub-pattern words, respectively, each j-bit sub-pattern word representing a signal component in a respective sub-period of the wave group, which comparator forms each time a combination word from a first sub-pattern word and a second sub-pattern word originating from corresponding sub-periods, which comparator also comprises a code number generator means for assigning a code number from a predetermined series of code numbers to each combination word, which code numbers represent a respective measure of the shift in time of the signal components, as represented by the first sub-pattern word of their respective combination word, with respect to the signal component as represented by the second sub-pattern word of their respective combination word, which control member also comprises a counter system which is connected to the code number generator means and which is suitable for determining for each of the code numbers a first sum number which indicates the number of times that the relevant code number has been assigned within one and the same cycle, which control unit is suitable for checking whether the first sum numbers exceed limit values given by a predetermined criterion and for activating the signal generator when the criterion is exceeded.

A method for continuously monitoring a physical integrity of a medium, said method comprising the steps of:

(a) repeatably generating a standard source pattern of substantially periodic nature and limited length, and coupling said source pattern to said medium for transmission therethrough;
(b) for each source pattern, after said transmission sampling a received pattern on a sequence of sampling instants, each such sequence having a substantial identical time relationship with respect to the generation of the associated source pattern;
(c) digitizing the results of each sampling instant to a digitized value, for generating a sequence of digitized values;
(d) for each said sequence of digitized values, forming a set of sub-patterns, each set having a substantial identical time relationship with respect to the generation of the associated source pattern and each sub-pattern comprising at least two contiguous digitized values of their sequence of digitized values;
(e) between two sequences of digitized values associated to respective source patterns, comparing pairs of corresponding members of the sets of sub-patterns, and for each pair detecting either an identity, or an apparent signed phase shift not exceeding a predetermined amount, or another difference category;
and
(f) calculating an overall trend in said apparent phase shift, and an overall difference among the sequences of digitized values in question;
generating an alarm signal in case said overall difference exceeds a standard difference value, wherein said standard difference value is smaller for a lower value of said overall trend and is higher for a higher value of said overall trend.

5 more elements

Dependencies are inferred from the claim text.