Programmable Logic Controller (PLC) Questions and Answers – 2

Suppose we have a PLC connected to three process switches as shown in this illustration:

In the above diagram :

• X1 to X4 : Inputs
• Y1 to Y4 : Outputs

Determine the switch actuation statuses (i.e. low versus high process stimulus) given the “live” display of the ladder logic program shown here:

Also, determine the status of the lamp connected to the PLC’s Y1 output.

Answer : 

• High pressure and low flow and low temperature.
• The lamp will be de-energized.

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Credits :  Tony R. Kuphaldt – under CC BY 1.0

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