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29.2 ANALOG OUTPUTS
After we have used a controller equation to estimate a value to put into our process, we must convert this from a digital value in the computers memory, to a physical voltage.
This voltage is typically limited to 20mA in most computer boards, and drawing near this current reduces accuracy and life of the board.
A simple circuit is shown below for a simple digital to analog converter.
The calculations for the A/D converter resolution and accuracy still apply.
29.2.1 Analog Outputs With A PLC
An example of an output card is 1771-OFE.
To output a value we only need to write a single value to the output card
The format for the block that is to be written to the card is shown below.
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