Communications: electrical – Continuously variable indicating – Via radiant energy beam
Reexamination Certificate
1999-05-19
2001-11-13
Zimmerman, Brian (Department: 2735)
Communications: electrical
Continuously variable indicating
Via radiant energy beam
C340S661000, C324S537000, C361S086000, C361S087000, C361S042000
Reexamination Certificate
active
06317056
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a circuit arrangement for the intrinsically safe detection of binary signals of a sensor.
Background Information
In accordance with DIN 19234 NAMUR, sensors, such as position sensors, are commonly used in areas subject to explosion hazard. By changing their internal resistance, these sensors generate binary signals which can be detected as different currents when a constant d.c. supply voltage is applied to the sensor.
SUMMARY
An object of the present invention is to allow a line interruption or short-circuit on the sensor side to be detected in addition to the intrinsically safe detection of binary signals.
Using voltage comparators which compare the current flowing through the measuring shunt to different constant partial voltages at the voltage divider, it is possible to define different current ranges which, in addition to the two binary states of the binary sensor signal, also identify a line interruption and a short-circuit on the sensor side. The comparison results supplied by the voltage comparators are advantageously transmitted to the analysis unit via optocouplers in order to provide electrical isolation between the sensor and analysis sides. For the same reason, a power supply unit that is used to supply power to the sensor contains a transformer. The number of optocouplers required can be reduced using a logic circuit, located downstream from the voltage comparators, which converts the possible combinations of comparison results of the voltage comparators to a minimum number of binary control signals needed for the optocouplers.
REFERENCES:
patent: 5287107 (1994-02-01), Gampell
patent: 5583731 (1996-12-01), Pergent
patent: 5818216 (1998-10-01), MacDonald
Klumpp Wolfgang
Morio Francis
Siemens Aktiengesellschaft
Staas & Halsey , LLP
Wong Albert K.
Zimmerman Brian
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