Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – Of individual circuit component or element
Patent
1989-12-19
1991-10-01
Wieder, Kenneth A.
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
Of individual circuit component or element
324601, 324605, 324612, G01R 3102
Patent
active
050537130
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an arrangement for monitoring detectors or transducers of the kind used to indicate different states.
By detector, hereinafter referred to as transducer is meant a device which is constructed to respond to a given event or occurrence, or to a given state and to produce accordingly a predetermined electric signal, which may constitute a measuring value or a predetermined state variable.
Such transducers are used in different automatic systems, such as industrial process control systems, or in complicated machines, such as aircraft among others.
The use of transducers for collecting input data for process control purposes stands and falls on the reliability of the transducers used in the system. This is emphasized by the fact that in an automatic process, about 80% of the downtime periods and distrubances experienced in operation are caused by malfunctioning of the transducers used.
The nature of this problem is accentuated when an automatic process is monitored and controlled by a computer system.
The problem is solved by the present invention, which proposes that the function of such transducers is monitored.
Accordingly, the present invention relates to an arrangement for monitoring transducers which are intended to produce an analogue or digital output signal corresponding to a state sensed by the transducer or detector, and is characterised in that the transducer includes activatable and deactivatable elements which are intended to influence the transducer in a manner such that said transducer will produce a signal which deviates from the actual state sensed by the transducer; and in that the arrangement includes a control circuit which, in response to a given signal, is responsive in activating and/or deactivating said elements in a predetermined sequence; in that a control device is provided for detecting the output signal of the transducer and comparing changes in the output signal caused by activation and/or deactivation of said elements; and in that the control device is effective, through said comparison, in detecting whether or not the transducer function is correct.
Thus, the invention relates to an transducer of the kind which is intended to pass through a test mode in which the transducer or its detecting area in space is subjected to such changes that the event or the state which the transducer is intended to detect is simulated during the so-called test mode, i.e. when the transducer is tested, the transducer reporting the simulated event or state to a recieving device, such as a superordinal control system.
According to one embodiment of the invention, the test mode is initiated by the superordinal control system, such as a datorised control system. When the transducer is subjected to the test mode, it will send to the receiver signals which are compared with predetermined signals or values, these predetermined signals or values corresponding to those signals obtained from the transducer when its function is known to be correct. Thus, the transmission of the transducer signal from the transducer to the receiver is also tested, in addition to testing the transducer.
One method of using this type of transducer is for the function of the transducer to be tested systematically, prior to accepting a transducer signal, by calling and activating the test mode. In this way, prior knowledge can be obtained of those functional errors which are likely to occur, which provides basis for a systematic and ordered error correction.
Another method of using this type of transducer is afforded when systematic use of the test mode is combined with duplication of critical transducer functions. The probability that both of the transducers will produce an error signal simultaneously is low. The use of the test mode enables a faulty transducer to be replaced before both transducers produce a faulty transducer signal.
It is obvious that the inventive arrangement has a very wide field of use and that the arrangement is not restricted to a few, special fields in which transducers are
REFERENCES:
patent: 4155080 (1979-05-01), Kovacs
patent: 4162491 (1979-07-01), Gochis
patent: 4267505 (1981-05-01), Biglin
patent: 4307335 (1981-12-01), Paulson
patent: 4806847 (1989-02-01), Atherton et al.
patent: 4831362 (1989-05-01), Tsaprazis
patent: 4837508 (1989-06-01), Garnault
Mueller Robert W.
Wieder Kenneth A.
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