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UNITS, STANDARDS & DEFINITIONS - Coggle Diagram
UNITS, STANDARDS & DEFINITIONS
Introduction
Field of process control has many sets of units, standards and definition to describe its characteristics
Some of these are a result of historical use, some are for convenience, and some are just confusing
Units
Essential to use a well-defined units of measurement to ensure precise technical communication among individuals employed in technological disciplines
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In process control, particular set of units is used - SI units
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Pneumatic Signals
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When a sensor measures some variable in a range, it is converted into a proportional pressure of gas in a pipe
The pipe may be hundreds of meters long, but as long as there is no leak in the system, the pressure will be propagated down the pipe
Pneumatic signals are carried by tubing, usually PVC coated 1/4 or 3/8 inch diameter copper tubing
Maximum transmission distances are limited to at most 200m due to the loss in accuracy of the signal
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Definitions
Error
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For a controlled variable in a control system, error is the difference between the measured value of the variable and the desired value (the setpoint value)
Block Definitions
Control systems are often described in terms of blocks, e.g.
measurement block, controller block, etc
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