PLC Flashcards
PLCs are used to control electrical circuits that have DC, AC, or AC and DC current.
True
? grounding is the connection of machinery electrical systems to earth ground to reduce the chance of electrical shock by grounding all non–current-carrying exposed metal.
Equipment
Sources use electron flow through a(n) ? .
PNP Transistor
An automatically operated switch is a switch that is activated independent of a person or object.
True
Direct hardwiring decreases the difficulty of troubleshooting or modifying a circuit.
False
Terminal strips increase the ease of circuit modifications because most of the wires required to make a change are disconnected and reconnected at the terminal strip.
True
The number and type of I/Os cannot be changed in a fixed PLC.
True
The standard unit of memory for a PLC is the byte.
False
Personal computers (PCs) are the most common programming device used with PLCs.
True
PCs are used as programming devices on all sizes of PLCs.
True
Pushbuttons, selector switches, limit switches, and proximity switches are common input devices.
True
Input devices can be programmed in series, parallel, or in series/parallel combinations.
True
The placement of programming instructions can be used to minimize CPU scan time.
True
The ? file contains the following system-related information: CPU type, I/O configuration, and passwords.
System Program
Counter instructions are located in data table file 5.
True
A TOF instruction starts timing when the logic preceding the instruction on the rung changes from false to true.
False
A break is the number of contact positions per pole.
False
Contactors are required between a PLC output section and high-power load.
True
? relays draw high current when energized and produce high voltage spikes when deenergized.
Solid-State
For individual conductors, the color blue is used to identify AC wiring and the color red is used for DC wiring.
False
The model, rating, and configuration of the PLC and any accessories should be checked against the purchase order.
True
Program backup is the final step in PLC maintenance.
True
A test instrument with a rating of CAT III or higher must be used when taking measurements on an electrical system that includes a PLC so the instrument can be used anywhere within the indoor electrical circuits.
True
When the type of voltage (AC or DC) is unknown, a measurement should be taken with the meter set to measure DC voltage.
True
In-line current measurements can be taken only on DC circuits.
False
An undervoltage occurs when there is more than a 10% decrease in voltage for 0.5 cycles to one minute
False
An overvoltage occurs when there is more than a 10% increase in voltage for longer than one minute.
True
The output voltage from a transformer should not drop more than 15% from a no-load condition to a fully loaded condition.
False
When a PLC supplies an output voltage, the output power supply will have both a voltage rating and a current rating.
True
Digital circuits turn loads fully on or fully off.
True
A variable frequency drive cannot accept an analog signal from a 1-kiloohm to 10-kiloohm variable resistor (potentiometer), a 0-volt DC to 10-volt DC voltage source, or a 4-milliampere to 20-milliampere current source as a control signal.
False
A digital electrical circuit is a circuit in which the load can be in any operating condition between and including fully on and fully off.
False
A variable frequency drive outputs an analog signal to a motor that changes the speed of the motor by changing the frequency and current applied to it through its operating range.
False
Digital circuits operate using binary signals that have only ? operating states
2
Analog sensors can only be connected to analog input terminals on a PLC.
True
A relay that uses electronic switching devices in place of mechanical contacts
solid-state relay
A system that interconnects two or more primary systems to combine the individual advantages of each system to meet the requirements of a given application
Combination system
A primary system in which electricity is monitored and controlled to send and/or receive information, produce sound or vision, store data, control circuits, or perform other work
Electronic System
The number of time base interval a timer instruction is programmed to accomplish
timer preset value
A PLC programming instruction used to track the length of time a machine has been operating or to shut down a process after and accumulative time period of recurring faults.
retentive time (RTO) instruction
The number of counts a counter has recorded
counter accumulated value
A type of programming timer that is continuously timing because the XIO instruction preceding the timer is always true
free running (repetitive) timer
A PLC programming instruction used to keep track of the number of items involved in sinprocess
count down (CTD) instruction
The section of software that contains information on the processor mode, edit status, force status, and communication drivers of a PLC
online bar
A button that is animated when a PC is online with a PLC
Online Icon
The rapid making and breaking of mechanical switch contacts when switch contacts are closed
contact bounce
A symbol in a flowchart that indicates the beginning and end of a section of a chart.
ellipse symbol
A PLC state of operation where the operating cycle of the PLC is not running, but the CPU is ready to accept information
Program mode
A PLC software operation where a PC is monitoring the PLC program and graphically displaying the state of all input and output terminals.
On-line monitoring
Maintenance that verifies that the master control relay (MCR) is functioning correctly, voltages are within specified range, and no abnormal conditions exist.
energized maintenance
The ability of carious pieces of equipment to work together with carrying level of noise emission immunity
electromagnetic compatibility(EMC)
A check that verifies that a PLC program functions properly without the application or process the PLC controls actually being run
program check
A set of procedures consisting of systematic checks
PLC startup
A check that verifies that all output components function properly and are wires to the correct PLC output terminal
output section check
A digital data signal from an external source
serial communication signal
A voltage that originates outside a PLC enclosure, such as voltage from an eclectic motor drive
foreign control voltage
A place on a contact that opens or closes an electrical circuit
break
The movement of a load (in pounds) over a distance (in feet)
Work
A system or device that allows primary systems to work and/or communicate as one.
interfacing system
A primary system that monitors operations, displays quantities (values), and indicates the status of machines and processes
information system.
