PLC Chapter 2 Review
#1 What is the function of a PLC input interface module? - Answer-To accept signals from the machine
or process devices and to convert them into signals that can be used by the controller
#2 What is the function of a PLC output interface module? - Answer-To convert controller signals into
external signals that are used to control the machine or process
#3 With reference to a PLC:
What is a remote rack?
Why are remote racks used? - Answer-a) A rack that is located away from the processor module near
the field devices
b) To minimize the amount of wiring required
#4 How does the processor identify the location of a specific input or output device? - Answer-By its
address
#5 List the three basic elements of rack/slot-based addressing. - Answer-Type refers to an input or
output
Slot refers to the physical location of the I/O module
, Word and bit refers to the actual module terminal connection
#6 Compare bit level and word level addressing. - Answer-Bit level addressing specifies a discrete device
that is connected to a specific terminal. Word level addressing specifies an analog device connected to a
module that uses a word of information.
#7 In what way does tag-based addressing differ from rack/slot-based addressing? - Answer-In tag-
based addressing you use a tag (alphanumeric name) to address data (variables). In rack/slot-based
addressing a fixed numeric format is used to identify the address data.
#8 What do PC-based control systems use to interface with field devices? - Answer-An input/output PC
interface card
#9 What type of I/O modules have both inputs and outputs connected to them? - Answer-Combination
I/O modules
#10 In addition to field devices what other connections are made to a PLC module? - Answer-
Connections for the power supply
#11 Most PLC modules use plug-in wiring terminal strips. Why? - Answer-For ease of wiring and
replacing modules
#13 With reference to PLC discrete input modules:
What types of field input devices are suitable for use with them?
List three examples of discrete input devices. - Answer-ON/OFF devices such as selector switches,
pushbuttons and limit switches
#14 With reference to PLC output modules:
#1 What is the function of a PLC input interface module? - Answer-To accept signals from the machine
or process devices and to convert them into signals that can be used by the controller
#2 What is the function of a PLC output interface module? - Answer-To convert controller signals into
external signals that are used to control the machine or process
#3 With reference to a PLC:
What is a remote rack?
Why are remote racks used? - Answer-a) A rack that is located away from the processor module near
the field devices
b) To minimize the amount of wiring required
#4 How does the processor identify the location of a specific input or output device? - Answer-By its
address
#5 List the three basic elements of rack/slot-based addressing. - Answer-Type refers to an input or
output
Slot refers to the physical location of the I/O module
, Word and bit refers to the actual module terminal connection
#6 Compare bit level and word level addressing. - Answer-Bit level addressing specifies a discrete device
that is connected to a specific terminal. Word level addressing specifies an analog device connected to a
module that uses a word of information.
#7 In what way does tag-based addressing differ from rack/slot-based addressing? - Answer-In tag-
based addressing you use a tag (alphanumeric name) to address data (variables). In rack/slot-based
addressing a fixed numeric format is used to identify the address data.
#8 What do PC-based control systems use to interface with field devices? - Answer-An input/output PC
interface card
#9 What type of I/O modules have both inputs and outputs connected to them? - Answer-Combination
I/O modules
#10 In addition to field devices what other connections are made to a PLC module? - Answer-
Connections for the power supply
#11 Most PLC modules use plug-in wiring terminal strips. Why? - Answer-For ease of wiring and
replacing modules
#13 With reference to PLC discrete input modules:
What types of field input devices are suitable for use with them?
List three examples of discrete input devices. - Answer-ON/OFF devices such as selector switches,
pushbuttons and limit switches
#14 With reference to PLC output modules:
