Electricity: measuring and testing – Plural – automatically sequential tests
Patent
1989-12-14
1991-09-03
Wieder, Kenneth A.
Electricity: measuring and testing
Plural, automatically sequential tests
324158R, 34087002, G08S 2300
Patent
active
050457764
DESCRIPTION:
BRIEF SUMMARY
This invention relates to metering apparatus and in the most important example to apparatus for metering usage of public utilities such as gas and water.
There have been many proposals made for utility metering apparatus which provides not only a visual representation of meter output but also an encoded electrical output which can be "read" by interrogation over a suitable communications link or through the use of portable meter reading apparatus. Conventional metering apparatus empolys a bank of number wheels driven to represent the meter output and attention has been focused on adapting such apparatus to provide an encoded output.
In certain prior proposals, a wiper contact on each number wheel makes contact successively with an array of position contacts. By applying appropriate electrical signals to the wiper contacts and monitoring the signals appearing on the position contacts, it is possible to provide an electrical output representative of the number wheel positions. It will be apparent that utility metering apparatus is required to operate substantially continuously without maintenance over extremely long periods of time. Because of wear or corrosion, mechanical faults may occasionally arise in the contact structures. Such faults will not necessarily prevent operation of the apparatus but will often result in erroneous electrical indications of the meter reading. Thus, for example, spreading of contacts through wear, or the deposition of conducting material between contacts, can lead to short circuiting of two or more adjacent position contacts. Such short circuiting can lead to significant errors in the meter reading. Whilst the likelihood of a fault arising on any particular meter is small, the potentially large number of meters to be included in a utility billing system and the significance of any error in the amount billed for utility usage, means that this problem demands careful attention.
It is an object of this invention to provide improved metering apparatus having provision for detection of such faults as outlined above.
Accordingly, the present invention consists in metering apparatus comprising a metering device having an output; a plurality of indicator elements driven in response to the meter output such that the orientation of the respective indicator elements is indicative of the meter output; for each indicator element an array of position contacts, corresponding position contacts from each said array being connected with a corresponding one of a plurality of position terminals, and a wiper contact disposed to make contact successively with the position contacts of the array on driving of the corresponding indicator element; generator means for applying, in a measurement mode, measurement signals in sequence to the wiper contacts and for applying, in a test mode alternating with the measurement mode, test signals in sequence to the position terminals; encoder means connected with the position terminals and adapted to provide an encoded output representative of the signals on said position terminals; and data output means arranged to receive said encoded output and adapted, in synchronism with operation of the generator means, to provide a data output, said data representing in the measurement mode the position of the respective indicator elements and, in the test mode, a test output in which departure from a predetermined value is representative of short circuiting of two or more position contacts.
The invention will now be described by way of example with reference to the accompanying drawings in which:
FIG. 1 is a block diagram illustrating electronic circuitry forming part of metering apparatus according to this invention;
FIG. 2 is a somewhat diagramatic section through mechanical parts of metering apparatus according to this invention;
FIGS. 3 to 8 are more detailed circuit diagrams of respective parts of the circuits shown in block form in FIG. 1;
FIG. 9 is a timing diagram illustrating the operation of the circuitry shown in FIG. 1;
FIG. 10 is a logic truth table illustrati
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patent: 3676876 (1972-07-01), Dransfield et al.
patent: 3778795 (1973-12-01), Campman et al.
patent: 3840866 (1974-10-01), St. Clair et al.
patent: 4652877 (1987-03-01), Gray
patent: 4688038 (1987-08-01), Giammarese
patent: 4782341 (1988-11-01), Gray
ABB Kent PLC
Nguyen Vinh P.
Wieder Kenneth A.
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