Patent ID: 6034612
Filing Date: 2000-03-07
Classification: G05B

Abstract:
A device for monitoring a machine to facilitate safe operation of the machine, the monitoring device comprising:at least two channels for monitoring system operating states, each channel having,a voltage source including a current output which is decoupled from said current outputs of said other voltage sources of said other channels,a signalling unit having a power supply input coupled to said current output via a first line, and a signal output, andmeans for varying the voltage fed into the first line;a test control circuit common to all said channels, said control circuit having a plurality of control outputs, each one of the control outputs corresponding to a different one of the channels, said control circuit controlling each said varying means such that,while no test cycle is running, all the signalling units are supplied with voltage, andduring a test cycle, either (1) each signalling unit is sequentially supplied with voltage in an intermittent temporary fashion, such that only one of the signalling units is supplied with voltage at a time, or(2) only one of the signalling units is not supplied with voltage at any one time, such that during the test cycle each signalling unit sequentially receives no voltage in an intermittent temporary fashion, or (3) the cycles (1) and (2) are performed sequentially or in an interleaved fashion; andan evaluation and control circuit having, per signalling unit, at least one normal input and at least one test input, the normal inputs generally continuously evaluating the operating state of the signalling units during normal operation, and the test inputs each receiving a signal which is derived from a voltage signal which is present at the power supply input of a corresponding one of the signalling units.