Information: The Industrial Maintenance practice test (or employment test) is for beginning and experienced mechanics to brush up on terminology and procedures. Some of the procedures are different for different companies, such as time for motor rotation or if they do motor rotation as a P.M. procedure. Some procedures are the same throughout the industry, such as "Lockout/Tagout procedures". These tests should help. Visit often as more tests and references are being added, including mechanical, electrical, hydraulic, general industrial tests and math for trades tests.

Industrial Maintenance practice test (It covers Electro-Mechanical and PLCs)
(85 questions)
Source = Industrial Maintenance practice test

39. The proximity switch _________
Ans. senses the approach of a metallic machine part either by a magnetic or high frequency electromagnetic field. when objects are near by
Proximity sensor
A proximity sensor is a sensor able to detect the presence of nearby objects without any physical contact.
What Are Proximity Switches?
Proximity switches are used to detect the "proximity" or presence of an object. Types of proximity switches; Optical Proximity Switches, Magnetic Proximity Switches, Ultrasonic Proximity Switches, Inductive Proximity Switches, Capacitive Proximity Switches

40. Calculate the synchronous speed of a rotating magnetic field created by the stator given the following information: # of poles: 4 frequency: 60Hz phases: 2
Ans. srpm=120xF/P 120X60/4=1800srpm

41. Four resistors having a value of 100 ohms each are connected in parallel. What is the total resistance of this circuit?
Ans. 1/100 + 1/100 +1/100 + 1/100= 25 ohms

42. Identify ohms law
Ans. V= IxR

43. What is the purpose of the test equipment Galvanometer?
Ans. Type of Ammeter
A galvanometer is a type of sensitive ammeter: an instrument for detecting electric current.

44. When using a multimeter to measure an output voltage, you should ensure that the dc voltage component does not exceed what maximum voltage?
Ans. .707% of full deflection

45. What is a coulomb?
Ans. unit of electric charge, equal to the quantity of electricity conveyed in one second by a current of one ampere.

46. What is the decimal value of the highest symbol in the hexadecimal system?
Ans. F=15 0-9A-F

1. Which device do you use to measure voltage?
Ans. multi meter
How to Use A Multimeter
introduces you to using a multimeter to make measurements from circuits
A typical multimeter would include basic features such as the ability to measure voltage, current, and resistance.

2. If you were asked to check out the I/O card on a plc, which card would you look at?
Ans. input card
PLC Input cards
PLC programming, tutorial, training, hints and tips.
PLC Programming ladder logic examples
Here you will find common PLC   programming ladder logic examples for programmable logic controllers I will also add descriptions and information later for operation and setup:
PLC Input/Output (I/O) Capabilities
Every programmable logic controller must have some means of receiving and interpreting signals from real-world sensors such as switches, and encoders, and also be able to effect control over real-world control elements such as solenoids, valves, and motors.

3. What does the term current refer to while dealing with electricity?
Ans. amps

4. On a hydraulic pump if you were told the pump is cavitating, what would you check for?
Ans. low fluid in the tank
Hydraulic Pumps & Cavitation
Causes: When the pump's fluid supply is not delivered appropriately, cavitation can occur. It can also be caused by low fluid levels or excessive resistance in the pump's supply lines.

5. In a 480 volt three phase system, what would your meter read if you went from one leg to ground?
Ans. 277 volts
What is the typical 460 3 phase voltage 1 leg to ground
In a transformer with a primary connected to 480V Delta and a secondary connected in 480V Star connection, the coil voltages to the star point (ground) are 277 volts 480/1.73 = 277 volts.


47. What term describes the use of four binary digits to represent on decimal digit?
Ans. BCD Binary Code Decimal

48. An electric motor has an apparent resistance of 15 ohms. If 8 amps of current are flowing through the motor, what is the connected voltage?
Ans. 120v

49. Newly installed motor runs in reverse direction, state the suspected fault?
Ans. leads L1 and L3 may need to be reversed

50. What test equipment is used to measure KW?
Ans. Wattmeter

* *51. What test equipment is used to measure kva
Ans. clamp on ammeter

52. What is the most common type of rotor used in a 3phase AC motor?
Ans. squirrel cage
AC motor
An AC motor is an electric motor driven by an alternating current (AC). It commonly consists of two basic parts, an outside stationary stator having coils supplied with alternating current to produce a rotating magnetic field, and an inside rotor attached to the output shaft that is given a torque by the rotating field.
Induction Motor
An induction motor has basically two parts: Stator and Rotor. The stator is made up of various stampings with slots to carry three phase windings. The rotor is the rotating part of the electromagnetic circuit. The most common type of rotor is the squirrel cage rotor.

53. What is the formula required to calculate the proper Phase voltage across single phase to neutral, and what voltage indicates a good reading, given its rating: 3phase 4wire, 240V motor.
Ans. 240/1.73=138 volts

6. Which tool is used when measuring Screw Pitch
Ans. thread gage
How to Measure Bolt Thread Size Measure the thread pitch. If you have a thread pitch gauge, mesh the serrated edge of each gauge arm in turn with the bolt thread. Note the value stamped on the arm that meshes tightly with the thread.

7. What is a circuit breaker?
Ans. an automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit.
Circuit breaker
A circuit breaker is a manually or automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit.

8. What does a D.P.S.T. switch refer to?
Ans. double pole single throw
"Equivalent to two SPST switches controlled by a single mechanism. The number of "poles" is the number of separate circuits which are controlled by a switch. For example, a "2-pole" switch has two separate identical sets of contacts controlled by the same knob. The number of "throws" is the number of separate positions that the switch can adopt. A single-throw switch has one pair of contacts that can either be closed or open. A double-throw switch has a contact that can be connected to either of two other contacts.

9. How many teeth are on a 40B12 sprocket?
Ans. 12
Roller Chain & Sprockets
12 Tooth, No. 40, 1/2" Pitch, Steel Min. Plain Bore Sprocket & Hub, 40b12
40B12 Sprocket, 2.17" OD, 12 Teeth, #40 Chain Size
Resource Center - Various Helpful Information: formula to find belt or chain length; nema electric motor frame chart; stuff you need to know (conversions, calculators, dictionary and more)

10. The BCD equivalent of 1247 converts to_____.
Ans. 0001 0010 0100 0111


54. What is the purpose of a steam trap?
Ans. discharge condensation and non condensables

55. State the formula and SI units for PRESSURE
Ans. P=F/A F=PxA

56. State the formula and SI units for AREA OF A TRIANGLE
Ans. A=1/2xBxH

* *57. State the formula and SI units for AREA OF A CIRCLE
Ans. A=PIxR,2

* *58. State the formula and SI units Volume of cylinder
Ans. V=PIxR,2xH

59. A fundamental rule of liquids that makes them suitable for use in hydraulic operations is that liquids are essentially _____.
Ans. Incompressable

60. List 3 primary reasons for lubrication.
Ans. seal out dirt and contaminants. reduce friction. prevent corrosion

11. What is the binary value of the following terms: Word and Nibble
Ans. 16 digit and 4 digit
What is mean by bit,byte,nibble and word?
Your talking about binary...A single digit of a binary number is a bit, A nibble is 4 bits (half a byte)...A byte is 8 bits... A word is 2 bytes (16 bits)

12. What type of programming is used by PLCs.
Ans. ladder logic
Types of PLC Programming
At present there are three different techniques in which PLC programming operates: ladder logic, state logic and traditional programming.

13. What is the Octal and Hexadecimal= 0-9,A,B,C,D,E,F equivalent for the decimal numbers
Ans. 1-15... 0-7, 10-17, 20... and 0-9,A,B,C,D,E,F

14. Typical BCD input devices include ____.
Ans. thumbwheel switches.
PLC BCD input devices
Binary-Coded Decimal (BCD) are decimal numbers where each digit is represented by a four-bit binary number. BCD is commonly used with input and output devices.


61. What does “N.P.T.” stamped on the side of a Tap stand for
Ans. National Pipe Thread
National pipe thread
National Pipe Thread Taper (NPT) is a U.S. standard for tapered threads used on threaded pipes and fittings. In contrast to straight threads that are found on a bolt, a taper thread will pull tight and therefore make a fluid-tight seal.

62. Which motors are associated with the term Slip
Ans. Synchronous. The difference between the synchronous speed of the magnetic field, and the shaft rotating speed is slip

63. Needle Valve
Ans. Regulate accurate flow control
Needle valve
A needle valve is a type of valve having a small port and a threaded, needle-shaped plunger. It allows precise regulation of flow, although it is generally only capable of relatively low flow rates.

64. Ball Valve
Ans. Quick acting, 90* on/ off control. No Pressure drop
Ball valve
A ball valve is a valve with a spherical disc, the part of the valve which controls the flow through it. The sphere has a hole, or port, through the middle so that when the port is in line with both ends of the valve, flow will occur. When the valve is closed, the hole is perpendicular to the ends of the valve, and flow is blocked. The handle or lever will be inline with the port position letting you "see" the valve's position.

65. Gate Valve
Ans. Used for isolation during fluid flow
Gate valve
The gate valve is a valve that opens by lifting a round or rectangular gate/wedge out of the path of the fluid. The distinct feature of a gate valve is the sealing surfaces between the gate and seats are planar, so gate valves are often used when a straight-line flow of fluid and minimum restriction is desired.

15. The BCD equivalent of 1247 converts to_____.
Ans. question 10

16. BCD code stands for _____.
Ans. binary coded decimal
Binary-coded decimal
In computing and electronic systems, binary-coded decimal (BCD) is a class of binary encodings of decimal numbers where each decimal digit is represented by a fixed number of bits, usually four or eight

17. The decimal 1000 has a Weighted Value Position of ______.
Ans. 3
Place Value
Each position in a decimal number has a value that is a power of 10. A decimal point separates the non-negative powers of 10 (10^0=1, 10^1=10, 10^2=100, 10^3=1,000, etc.)

18. If in binary a zero signifies an OFF state a one signifies____________.
Ans. an ON state

19. How many symbols are in the octal number system?

20. To convert from binary to octal, you select bits in groups of ____
Ans. 3
How to Convert Binary to Octal Number
1. Block off the digits of your binary string into sets of three starting from the right.
2. Convert the rightmost three digit block (or less) to a single value,
3. Because a set of three digits in binary will always be between 0 and 7, the result will be an octal value.


66. Globe Valve
Ans. A linear motion valve used to stop, start, and regulate fluid flow. Most common valve in a propulsion plant
Globe valve
A globe valve, different from ball valve, is a type of valve used for regulating flow in a pipeline, consisting of a movable disk-type element and a stationary ring seat in a generally spherical body.

67. Check Valve
Ans. used to prevent backflow. Fluid flows in one direction
Check valve
A check valve, clack valve, non-return valve or one-way valve is a valve that normally allows fluid (liquid or gas) to flow through it in only one direction.

68. butterfly valve
Ans. Start, stop, and regulates large flow at low pressure
Butterfly valve
A butterfly valve is a valve which can be used for isolating or regulating flow. The closing mechanism takes the form of a disk.

69. A device used to transfer heat energy from one fluid to another without direct contact is called
Ans. heat exchanger
Heat exchanger
The counter current design is the most efficient, in that it can transfer the most heat from the heat (transfer) medium due to the fact that the average temperature difference along any unit length is greater.

70. Fluid power which uses compressed air to affect mechanical motion is called _____________________.
Ans. Pneumatics
Pneumatics is a section of technology that deals with the study and application of pressurized gas to produce mechanical motion.

21. A register or word is composed of ____.
Ans. sixteen bits or two bytes.
PLC Basics
the Programmable Logic Controller (or PLC) has become an essential aspect of any automated manufacturing process. PLCDev has developed this instruction manual "PLC Basics" in hopes it will serve the beginner to the advanced user.
Introduction to PLCs
Programmable Logic Controllers, also called Programmable Controllers or PLCs, are solid state members of the computer family, using integrated circuits instead of electromechanical devices to implement control functions.
PLC Technical Terms
Glossary of PLC hardware and programming technical terms

22. What type of programming is used by PLCs
Ans. ladder logic
Types of PLC Programming
A programmable logic controller (PLC) is a type of computer used particularly for industrial purposes, such as the automated processing of electromechanical activity on factory machinery.

23. The two basic sections of a PLC are the _____.
Ans. the central processing unit (CPU) and the input/output system
What is a PLC?
A PLC consists of two basic sections: CPU and Input/Output.

24. State the primary sections of PLCs .
Ans. Input modules, (CPU) Central Processing Unit, Output modules, Programming device, Operator Interface Device
Knowing the basics of PLCs
Common to all PLCs are four sections. These primary sections include the power supply section, the program software section; the CPU module, and the I/O section.


71. A type of bearing used to withstand axial forces which push or pull along the bearing axis is called a __________________.
Ans. Thrust bearing
Thrust bearing
A thrust bearing is a particular type of rotary bearing. Like other bearings they permit rotation between parts, but they are designed to support a predominately axial load.
How Does a Thrust Bearing Work?
Thrust bearings absorb axial loads from rotating shafts into the stationary housings or mounts in which they are turning.

72. A type of bearing designed to withstand forces perpendicular to the axis or shaft is called a __________________.
Ans. Radial bearing
Radial Bearings
The purpose of a radial bearing is to reduce rotational friction and support loads. This is achieved by using two races to hold the balls and to spread the load through the balls.
Ball bearing
The purpose of a ball bearing is to reduce rotational friction and support radial and axial loads. It achieves this by using at least two races to contain the balls and transmit the loads through the balls.

73. A type of bearing which uses long, thin cylinders to move in an oscillary motion rather than rotary__________________.
Ans. Needle bearing
Needle Roller Bearings
Needle roller bearings incorporate rollers that are three to ten times longer than their diameter and exhibit a relatively large radial load capability
Needle roller bearing
A needle roller bearing is a bearing which uses small cylindrical rollers.The difference of a needle roller bearing and roller bearing is the ratio of diameter and length of their rollers, when the ratio of the diameter and the length of roller of a roller bearing is between the interval of 0.4 to 0.1, that roller bearing is called as needle roller bearing.

74. It is stated that 1 cubic foot of water weighs 62.4 pounds. Using Pascal’s law for force, calculate the pressure on the bottom of the container.
Ans. 62.4/144in= .433lbft

75. What are the five basic components associated to a Hydraulic system and discuss each of their functions?
Ans. 1.Reservoir-Holds the hydraulic fluid. 2.Pump-generates flow in the system. 3. Valves- Controls the hydraulic fluid. 4 Actuators- Cylinders and Motors. 5- Connectors/Conductors-hook components together to form a system.
Operation of Hydraulic Components
To transmit and control power through pressurized fluids, an arrangement of inter- connected components is required. Such an arrangement is commonly referred to as a system.
Hydraulic System Components and How they Work
Hydraulic systems perform an important role in today's machinery and equipment. Hydraulic systems allow the relatively efficient transfer of large amounts of power and force via a hydraulic fluid.

76. Name 4 types of liquids used with Hydraulic systems.
Ans. petroleum based, phosphate ester, synthetic- fire resistant, water based- fire resistant
Types of Hydraulic Fluids
Types of Hydraulic Fluids. There have been many liquids tested for use in hydraulic systems.

25. PLC Input modules convert_______________
Ans. signals(analog or discrete/digital) provided by various switches and sensors into logic that can be used by the CPU
Digital Input
Digital Input Module for PLC/PAC/DCS – System Block Diagram. Digital input modules capture and measure digital input signals from a wide variety of sensors like proximity switches, limit switches and push button switches. Inputs typically are 0-24V with tolerances up to 30V.

26. What solid state device is associated with the term “avalanche effect”?
Ans. Zener diode
Zener diode
A Zener diode is a diode which allows current to flow in the forward direction in the same manner as an ideal diode, but also permits it to flow in the reverse direction when the voltage is above a certain value known as the breakdown voltage.

27. The SCR is equivalent to what electronic device?
Ans. thyristor
A thyristor is a solid-state semiconductor device with four layers of alternating N and P-type material. They act as bistable switches, conducting when their gate receives a current trigger, and continue to conduct while they are forward biased
Silicon-controlled rectifier (SCR)
A silicon-controlled rectifier (or semiconductor-controlled rectifier) is a four-layer solid state current controlling device. The name "silicon controlled rectifier" is General Electric's trade name for a type of thyristor.

28. What does the PLC Central Processing unit ( CPU) do?
Ans. evaluates the status of inputs, outputs, and other variables as it excutes a stored program. The CPU then sends signals to update the status of outputs.
Programmable Logic Controller (PLC)
Central Processing Unit (CPU) The CPU controls and supervises all operations within the PLC, carrying outprogrammed instructions stored in the memory. An internal communications highway, or bus system, carries information to and from the CPU, memory and I/O units, under control of the CPU

29. Describe the function of Output Modules
Ans. Output Modules convert control signals from the CPU into digital or analog values that can be used to control various outputs
PLC/DCS I/O Module: Analog Output
Analog output modules are used to drive and control actuators and other machines and form part of an overall control system. Current-loop outputs typically range from 4-20mA while voltage outputs range from 0-5V, 0-10V, +/-5V and +/-10V.
What you need to know about PLC Outputs
PLC Outputs are the control circuits of the PLC and also refers to the devices controlled by the PLC. Be aware when talking about PLCs the devices like motors and lights are also referred to as PLC Outputs. Devices called actuators convert the electrical signal of the PLC to a physical movement for instance a valve solenoid stoke or a motor contactor.
Troubleshooting PLC Digital Output Modules, Part 1
As with the input modules, your first step in troubleshooting is to determine what power should be present and where it comes from. Your second step is to check the output module fuse indicator. It's possible the indicator is faulty, so check the fuse directly if there's no “fuse blown” indication. Then, use a DMM to verify that the module power is what it’s supposed to be (e.g., 120V) at the terminals.


77. What is the most commonly used Hydraulic fluid and what some of its advantages?
Ans. mineral oil- petroleum based
Hydraulic fluid
Common hydraulic fluids are based on mineral oil or water

78. In a pipe kit, what is the function of the Die?
Ans. rethread male outside threads
Tap and die
Taps and dies are cutting tools used to create screw threads, which is called threading. A tap is used to cut the female portion of the mating pair (e.g., a nut). A die is used to cut the male portion of the mating pair (e.g., a screw).

79. What type of caliper is used for finding shaft centers or locating shoulders?
Ans. vernier
A caliper is a device used to measure the distance between two opposite sides of an object. Types: Inside calipers are used to measure the internal size of an object. Outside calipers are used to measure the external size of an object. The vernier, dial, and digital calipers give a direct reading of the distance measured with high accuracy and precision

80. What is meant by the schedule number marking found on a pipe, and what formula is used to determine the standards?
Ans. standardizing pipe thickness
schedule 40 and schedule 80 pvc
the very basic difference is that schedule 80 is thicker and stronger than schedule 40 pvc.
Markings on PVC Pipe
Standard plumbing grade pvc pipe is is marked with a universal standard code that tells you several things about the pipe.

81. Magnets only stick to ferromagnetic metals like iron, cobalt, and nickel. Magnets will not attract non-ferrous metals. List 3 types of non-ferrous metals.
Ans. Aluminium and its Alloys. Copper. Brass
Non-ferrous metal
In metallurgy, a non-ferrous metal is any metal, including alloys, that does not contain iron in appreciable amounts. Generally more expensive than ferrous metals, non-ferrous metals are used because of desirable properties such as low weight (e.g., aluminium), higher conductivity (e.g., copper),[1] non-magnetic property or resistance to corrosion (e.g., zinc).[2]

82. A gear with a small number of teeth (under approximately 20-25 teeth) is called a ______________________.
Ans. pinion
A pinion is a round gear usually the smallest gear in a gear drive train

83. A __________________ prevents a gear from sliding endwise.
Ans. setscrew

84. When two spur gears are in mesh, the number of teeth in one gear divided by the number of teeth in the other is called the ____________ _______________.
Ans. gear ratio
Gear ratio
The gear ratio of a gear train, also known as its speed ratio, is the ratio of the angular velocity of the input gear to the angular velocity of the output gear. The gear ratio can be calculated directly from the numbers of teeth on the gears in the gear train.

85. Why is flux used when soldering?
Ans. To prevent the formation of metal oxides at extreme temperatures
What Is Solder Flux Used for?
Solder flux is a type of metallurgy component used when soldering two metals together. The flux is an inert substance that prevents the formation of metal oxides at extreme temperatures.

30. What is the Programming Device used for?
Ans. it is used to enter or change the PLCs program or to monitor or change stored values. Once entered the program and associated variables are stored in the CPU
Programmable logic controller
PLCs are programmed using application software on personal computers, which now represent the logic in graphic form instead of character symbols. The computer is connected to the PLC through Ethernet, RS-232, RS-485 or RS-422 cabling. The programming software allows entry and editing of the ladder-style logic.

31. Discrete inputs and outputs, also referred to as digital inputs and outputs are_______________
Ans. either ON or OFF. High or Low
Digital I/O Fucctionality
In contrast to analog transducers that sense continuous variables such as pressure and temperature, many transducers provide an output that is one of two states: high or low, open or closed.

32. Pushbuttons, toggle, switches, limit switches, proximity switches, and relay contacts are all examples of______________
Ans. devices that are often connected to PLC discrete inputs.
PLC Based Automation
Pushbuttons, toggle switches, limit switches, proximity switches, and relay contacts are examples of devices often connected to PLC discrete inputs

33. Solenoids, relay and contactor coils, and indicator lamps are examples of______
Ans. devices often connected to PLC discrete outputs.
PLC Based Automation
pg.5 Solenoids, relay and contactor coils, and indicator lamps are examples of devices often connected to PLC discrete outputs

34. In the on condtion, a discrete input or output is represented internal to the PLC as_______
Ans. a logic 1
PLC Based Automation
pg.5 In the on condition, a discrete input or output is represented internal to the PLC as a logic 1.

35. In the off condition, a discrete input or output is represented as_____
Ans. a logic 0
PLC Based Automation
pg.5 In the off condition, a discrete input or output is represented as a logic 0.

36. Analog Inputs/Outputs are____________
Ans. continuous, variable signals
PLC Based Automation
pg.5 Analog Inputs and Outputs Analog inputs and outputs are continuous, variable signals. Typical analog signals vary from 0 to 20 milliamps, 4 to 20 milliamps, or 0 to 10 volts.

37. Typical analog signals vary from ________
Ans. 4 to 20 milliamps
PLC Based Automation
pg.5 Analog Inputs and Outputs Analog inputs and outputs are continuous, variable signals. Typical analog signals vary from 0 to 20 milliamps, 4 to 20 milliamps, or 0 to 10 volts.

38. Advantages of PLCs are____________
Ans. Smaller size, easier and faster system changes, integrated diagnostics, immediate documentation.
PLC Advantages and Disadvantages
Flexibility, Correcting Errors, Space Efficient, Low Cost, Testing, Visual observation.
Advantages of PLC
Following are just a few of the advantages of PLCs: • Smaller physical size than hard-wire solutions. • Easier and faster to make changes. • PLCs have integrated diagnostics and override functions. • Diagnostics are centrally available. • Applications can be immediately documented. • Applications can be duplicated faster and less expensively.



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PLCDev has developed this instruction manual "PLC Basics" in hopes it will serve the beginner to the advanced user. Our goal is to make it comprehensive as possible, providing not only the generic principles in all PLCs, but to give practical examples from many different PLC manufacturers.
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A programmable logic controller (PLC) is a digital computer used for automation of electromechanical processes, such as control of machinery on factory assembly lines, amusement rides, or lighting fixtures. PLCs are used in many industries and machines.
Programmable Logic Controllers CD/DVD
This highly innovative computer-based training (CBT) program combines advanced PLC simulation with one of the best-selling PLC books in history. Students learn the Logix 5000 PLC system – the industry standard with over 80% of the U.S. PLC market.
Programmable Logic Controllers (PLCs)
The PLC can be programmed like other computers using specialized “languages.” - Ladder Logic - a programming technique using a ladder-like structure. It was originally adopted because of its similarity to relay logic diagrams to ease its acceptance in manufacturing facilities. The ladder approach is somewhat limited by the lack of loops, etc. (although this is changing).
Glossary of Terms used in Programmable Controller-based Systems

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A PLC or Programmable Controller is a digital computer used for automation of electromechanical processes, such as control of machinery on factory assembly lines, amusement rides, or light fixtures.
Basics of plc
Welcome to another course in the STEP series, Siemens Technical Education Program. This course covers Basics of PLCs and related products.