This Portion of Electrical and Electronic Instrumentation contains Automatic Process Control MCQs (Multiple Choice Questions and Answers) / Objective Type Questions and Answers.
This Section covers below lists of topics.
- Programmable Logic Controllers
- Advantages of PLCs
- The Control Program
- Function of each Part in PLC
- Hardware of PLC
- System Addressing
- PLC Operation and Program Scan
- Implementation of Control Programs in PLC
- More in Ladder Logic
1. PLCs are ___________ designed for use in the control of a wide variety of manufacturing machines and systems.
- special-purpose industrial computers
- personal computers
- electromechanical systems
- all of the above
A. special-purpose industrial computers
2. The first company to build PLCs was
- general motors
- Allen Bradley
- square D
- Modicon
D. Modicon
3. Which of the following statements is not correct?
- The PLC rung output [-( )-] is a discrete output instruction or bit in memory
- Each rung of the ladder logic represents a logical statement executed in software—inputs on the right and outputs on the left
- Input and output instructions in ladder logic do not directly represent the switches and actuators.
- PLC input instructions are logical symbols associated with voltage at the input module terminals.
D. PLC input instructions are logical symbols associated with voltage at the input module terminals.
4. Which of the following statements is NOT correct?
- The status of each input can be checked from one location and outputs can be forced on and off
- All symbols in the RLL represent actual components and contacts present in the control system
- PLCs are not as reliable as electromechanical relays in RLL
- Input (-| |-) and output (- ( ) -) instruction symbols in the ladder logic represent only data values stored in PLC memory
C. PLCs are not as reliable as electromechanical relays in RLL
5. When a relay is NOT energised
- there is an electrical path through the NO contacts
- there is an electrical path through the NC contacts
- neither the NO or the NC contacts have an electrical path
- both the NO and the NC contacts have an electrical path
C. neither the NO or the NC contacts have an electrical path