AC input cell for data acquisition circuits

Details AC input cell for data acquisition circuits AC input cell for data acquisition circuits

1998-06-08

2001-05-08

Lam, Tuan T. (Department: 2816)

Miscellaneous active electrical nonlinear devices, circuits, and

Specific signal discriminating without subsequent control

By amplitude

C327S080000

Reexamination Certificate

active

06229349

ABSTRACT:

SUBJECT OF THE INVENTION
The present invention relates essentially to an AC input cell intended for data acquisition circuits, more particularly in railway applications.
TECHNICAL BACKGROUND
Currently, AC input cells intended for data acquisition circuits essentially consist of mechanical safety relays which are connected together by simple cabling.
OBJECTS OF THE INVENTION
The present invention aims to provide a cell for AC inputs intended for data acquisition circuits, particularly in railway applications, which has at least equivalent behaviour in terms of safety to that of the prior art, while keeping inherent advantages of compactness, easier maintenance and fitting as well as greater longevity.
More particularly, the present invention aims to provide a cell in which misreading always errs on the side of safety.
The present invention also aims to detect malfunctions which may occur in the various constituent elements of the cell.
The present invention furthermore aims to minimize the influence of a variation in the characteristics of the components which are used, under the effect of an external factor such as a rise in temperature, for example.
PRINCIPLE CHARACTERISTICS OF THE PRESENT INVENTION
The present invention relates to an AC input cell intended for data acquisition circuits, comprising at least one device for detecting a voltage greater than the reference for the positive half-cycle at the input voltage, and a device for detecting a voltage greater than the reference for the negative half-cycle of the input voltage.
Each of these detection devices comprises a Zener diode, an optocoupler comprising an emission LED, a diode and a resistor, these elements being arranged in series.
According to a first preferred embodiment of the present invention, the elements constituting each of the two detection devices mentioned above are arranged on one branch, the two branches being arranged in parallel.
In this case, the elements constituting the detection device for the negative half-cycle are arranged in a configuration which is the opposite to that of the ones constituting the detection device for the positive half-cycle.
According to another embodiment, the two detection devices are arranged in series on a single branch. In this case, the elements constituting the detection device for the negative half-cycle are mounted in a configuration which is the opposite to that of those constituting the detection device for the positive half-cycle.
Particularly advantageously, a resistor is arranged in parallel on each of the optocouplers, so as to make it possible to limit the influence of the leakage current of the Zener diodes.


REFERENCES:
patent: 4091292 (1978-05-01), Sibley
patent: 4712153 (1987-12-01), Marget et al.
patent: 5621394 (1997-04-01), Garrick et al.
patent: 0 183 406 A1 (1985-11-01), None

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