Electricity: measuring and testing – Conductor identification or location
Patent
1994-05-10
1996-09-03
Snow, Walter E.
Electricity: measuring and testing
Conductor identification or location
324539, G01R 1900, G01R 3102
Patent
active
055526993
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
When control systems are installed in buildings, it is necessary to check--after having connected all installed cables, which connect a field unit, such as a temperature sensor or a motor actuator, to a switch cabinet--each individual one of these cables so as to find out whether the connection in question is correct. The course of action which has hitherto been taken for this purpose is that a first person stands near the switch cabinet and a second person near the respective field unit. The cable is tested by means of a so-called "continuity test". The two persons can communicate with the aid of a radio set so that it is also possible to carry out function tests of the field units. In principle, it can, however, only be checked whether or not the wiring was carried out correctly. If it is observed that a specific cable does not lead to the associated field unit, it is impossible to find out by means of the known method where the mistake has been made or rather where the cable actually leads to. In medium-sized building projects, between 3000 and 10,000 cables are tested in this way. In view of the fact that two persons are required for carrying out the test, it is easily imaginable that the testing of the wiring alone already entails considerable personnel expenditure. This expenditure is increased enormously if errors occur in the form of confusions. In view of the fact that the known method is not suitable for finding out where the cables which have been exchanged by mistake lead to, it will normally be necessary to install the whole wiring again. Since the construction is already in an advanced stage in this phase, costs will again be incurred, which are much higher than those entailed by the original wiring.
A method of the type mentioned at the beginning is known from AU-B-0551 and also from the reference document U.S. Pat. No. 3,891,811. An automatic conductor pair identifier utilizes a field unit under the control of an operator and an office control unit coupled to a multiwire cable of wire pairs to be identified. Upon actuation of the field unit by an operator, a frequency tone signal is transmitted over a randomly selected wire pair to the office control unit that responds thereto to transmit a pulse code representing a number identifying the wire pair over the same wire pair. This pulse code is received by the field unit and converted into a digital display for operator evaluation. Basically, the field unit comprises an oscillator coupled to a transmitter for generating the inquiring frequency signal. A pulse code is received in the field unit by a level detector/receiver coupled to logic circuitry for decoding the pulse code to drive a units display and a tens display as part of a digital readout. In the office unit, there is also a receiver and level detector coupled to logic circuitry for responding to an inquiring frequency signal to set up a counting sequence. Upon positively identifying an inquiring frequency signal, the logic circuitry actuates a transmitter coupled to an oscillator for transmitting the pulse coded to the field unit over the same wire pair used by the field unit.
Another method is known from periodical Elektor Electronics, vol. 16 (1990), April, No. 177, GB-London, article "Wiring Allocation Tester". Both methods include the steps of applying digital signals to one end of the cable cores with the aid of a multiplexer, said digital signals being adapted to be read at the other end of the cable by means of an associated receiver. Due to the multiplex operation used, the number of cable cores to be tested is limited.
Hence, it is the object of the present invention to improve a method according to the generic clause and an associated apparatus in such a way that an arbitrary number of cables can be tested.
The present invention is directed to a method of testing the wiring between a switch cabinet and field units which are connected to the switch cabinet and which are installed at a large distance therefrom. The method includes applying to all
REFERENCES:
patent: 3182253 (1965-05-01), Dorsch
patent: 3891811 (1975-06-01), Miller
patent: 3902026 (1975-08-01), Rogers et al.
patent: 4916444 (1990-04-01), King
patent: 4937529 (1990-06-01), O'Toole
Snow Walter E.
Technoserv GmbH
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