Industrial and Control Chapter1

HW and Quiz practice problems

If all units are in a fixed enclosure, the PLC is:

fixed

There are four main components of a PLC’s power supply:

• varistor (line conditioner)

• full bridge rectifier

• RC filter

• ?

zener diode

_ is a semiconductor device that can maintain a steady state voltage

zener diode

__converts digital to analogue signals

digital to analogue converters

the __ segment holds the ladder logic program

user memory

the section of the PLC memory that holds the discrete input ports is the __ status

input

T/F: One benefit of PLCs over electromechanical relay logic systems is PLCs require minor wiring and can be

modified and reprogrammed within a few hours.

T

T/F: Discrete input ports are ports that are either open (off) or closed (on).

F

T/F: Static RAM (SRAM) stores data in the form of charge on capacitors.

F

T/F: The arithmetic logic unit (ALU) carries out math and logic instructions.

T

T/F: When selecting PLCs that meet your needs, you should consider manufacturer’s support, serviceability, and

programming software.

T

T/F: The user memory segment stores information needed to execute the user program.

F

T/F: Simplex channeling occurs when the DTE either transmits data to or receives data from the DCE.

T

T/F: In half duplex channeling, the DTE transmits data to and receives data from the DCE through two separate

transmission lines.

F

T/F: Sourcing occurs when the current flows out of the PLC port and sinking occurs when the current flows into

the PLC port.

T

What is the difference between a discrete PLC input port and a variable PLC input port?

• Discrete ports are either open or closed

• Variable inputs have variable input voltages or currents (0-5V and 4mA-20mA)

What is the difference between a Fixed PLC system and a Modular PLC system?

• Fixed PLCS: CPU, power supply and ports all in one housing

• Modular PLCs: CPU, power supply and ports are in separate slots

What are the four major components of a PLC device?

• CPU

• Power supply

• Input/output modules and chassis

What is the difference between system PLC memory and user PLC memory?

• system memory holds data for program execution

• user memory holds data for plc program

List five data held in PLC memory

• flag status file

• input file

• output file

• bit file

• timer

• counter file

• integer file

• control file