← All revision guidesSEMESTER 4 · DI04000201
6FLASHCARDSIndustrial Automation and Control
PLC hardware, ladder logic, sensors, actuators and industrial control.
PLC fundamentals
Q1Describe one PLC scan cycle.
The PLC reads inputs, executes the user program, updates outputs and performs diagnostics or communication.
Q2What is a seal-in contact in ladder logic?
An auxiliary contact of an energized output keeps that output true after the momentary start input is released.
Q3Why is an emergency-stop circuit normally hardwired?
A hardwired safety circuit can remove hazardous energy independently of ordinary program execution or communication.
Sensors and actuators
Q1When is an inductive proximity sensor used?
It detects nearby metallic objects without physical contact.
Q2What is the purpose of an interlock?
It prevents two incompatible or unsafe operations from occurring at the same time.
Q3Why is electrical isolation used between a PLC and a power circuit?
It protects low-voltage control electronics and users from high voltage, transients and ground-potential differences.