The LSDVC block contains all of the parameters found in the Discrete Output (LSDO) block. In addition, the LSDVC block performs automatic and manual partial stroke testing on the associated valve.
The following block diagram shows a simple application that uses the LSDVC block to operate a DVC6000ESD digital valve controller.
In this example, the input to the Digital Valve Controller block is an effect output from a Cause and Effect Matrix block. During normal operation the effect output's value is 1 (one). When the inputs to the Cause and Effect Matrix block indicate a hazardous condition exists, the effect output is set to 0 (zero). This, in turn, trips the output of the Digital Valve Controller block, driving the associated Logic Solver HART Two-state Output Channel or LS CHARM to the configured off-current value, which closes the valve.
The Discrete Input block is wired to a limit switch or other indicator to confirm that the valve closes. If the valve does not close, the PV input to the Digital Valve Controller block from the Discrete Input block eventually sets a fault state in the Digital Valve Controller block.
This simple example does not illustrate a number of configurable functions the block supports:
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Options for detecting a fault state
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Timers to delay sending a signal to close the valve or set the fault state
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Requiring permission before resetting the block to normal operation after being tripped.
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A number of features that support partial stroke testing
Refer to the Application Information section and the Alternative Implementation Example for more specific application information.