Name: Class: Date: MECH 1500 Midterm Review True/False Indicate whether the statement is true or false. 1. Normally, a binary 1 represents the presence of a signal, while a binary 0 represents the absence of a signal. 2. All gates are devices that have one input with which they perform logic decisions and produce a result at one or more of their outputs. 3. All inputs to an AND gate must be 1 to produce a 1 output. 4. All inputs to a NAND gate must be 1 to produce a 1 output. 5. Only one input to an OR gate must be 1 to produce a 1 output. 6. All inputs to a NOR gate must be 1 to produce a 1 output. 7. Inverting the output of an OR gate will result in creating a NOR gate. 8. The AND function, implemented using switches, will mean switches connected in parallel. 9. A two input OR function, expressed as a Boolean equation, would be Y= AB. 10. Hardwired logic refers to logic control functions determined by the way devices are interconnected. 11. Hardwired logic can be implemented using relays and relay schematics. 12. Hardwired logic is fixed and is changeable only by altering the way devices are connected. 13. Programmable control is based on logic functions that are programmable and easily changed. 1
Name: 14. There is no difference between a relay schematic and a ladder logic program. 15. On some PLCs, only one output is allowed per ladder logic rung. 16. One of the most common PLC programming languages is ladder logic. 17. Ladder logic is a graphical representation of a user program. 18. The decimal system uses the number 9 as its base. 19. All digital computing devices perform operations in binary. 20. The base of a number system determines the total number of unique symbols used by that system. 21. In any number system, the position of a digit that represents part of the number has a weighted value associated with it. 22. Usually a group of 8 bits is a byte, and a group of one or more bytes is a word. 23. To express a number in binary requires fewer digits than in the decimal system. 24. The octal number system consists of digits 0, 1, 2, 3, 4, 5, 6, and 7. There are no 8's or 9's. 25. The hexadecimal number system consists of 16 digits including the numbers 0 through 9 and letters A through F. 26. In the Gray code there is a maximum of one bit change between two consecutive numbers. 27. The radix of a number system is the same as the base. 28. Binary number systems use positive and negative symbols to represent the polarity of a number. 2
Name: 29. RAM memory is nonvolatile. 30. Digital modules are also called discrete modules. 31. The number and type of I/Os cannot be changed in a fixed PLC. 32. The scan time is the time required for one complete execution of the user program. 33. A personal computer communicates with the PLC processor via a serial or parallel data communications link. 34. The programmable controller operates in real time. Multiple Choice Identify the choice that best completes the statement or answers the question. 35. A gate is a device that: a. allows current flow in one direction only. b. changes alternating current to direct current. c. performs a logical decision based on its inputs. d. performs a logical decision based on its outputs. 36. The basic rule for an AND gate is: a. if all inputs are 1, the output will be 1. b. if all inputs are 1, the output will be 0. c. if all inputs are 0, the output will be 1. d. both a and b. 37. The basic rule for an OR gate is: a. if one or more inputs are 1, the output is 1. b. if one or more inputs are 1, output is 0. c. if one or more inputs are 0, the output is 1. d. both band c. 3
Name: 38. The NOT function can be thought of as: a. a FALSE-to-TRUE converter. c. an inverter. b. a changer of states. d. all of these. 39. The logic symbol shown is that of the: a. AND function. c. NOT function. b. OR function. d. NAND function. 40. The Boolean equation for the logic symbol is: a. Y= A + B c. Y= A B b. Y= AB d. either b or c. 41. The logic symbol drawn is that of the: a. AND function. c. NOT function. b. OR function. d. NOR function. 42. The Boolean equation for the logic symbol is: a. Y= A+B+C c. Y= (AB)+C b. Y = ABC d. Y = (A B)C 4
Name: 43. With reference to the logic circuit, the output Y will be at a logic 1 when: a. inputs A and B are logic 1. b. input A or B is logic 1. c. input A is at logic 1 and input B is at logic 0. d. input A is at logic 0 and input B is at logic 1. 44. The logic symbol drawn in that of the: a. AND function. c. NOR function. b. OR function. d. NAND function. 45. The logic symbol drawn is that of the: a. NOT function. c) NAND function. b. NOR function. d) OR function. 46. The Boolean expression for the logic circuit drawn is: a. Y = ABC c. Y = (A + B)C b. Y=A+B+C d. Y=AB+C 5
Name: 47. The Boolean expression for the logic circuit drawn in is: a. Y = (A B)(CD) c. b. d. Y= ABC + D 48. The Boolean expression for the logic circuit is: a. c. b. d. 6
Name: 49. Which of the hardwired relay schematics of is being implemented by the PLC program shown? a. (a) c. (c) b. (b) d. (d) 50. A OR gate operates on the same principle as: a. a series circuit. c. a series-parallel circuit. b. a parallel circuit. d. none of these. 51. A NOR gate is: a. an AND gate with an inverter connected to the output. b. an OR gate with an inverter connected to the output. c. equivalent to a series circuit. d. equivalent to a parallel circuit. 52. The number 12 is: a. 12 in any number system. c. 12 in binary. b. 12 in decimal. d. all of the above. 7
Name: 53. The octal number 153 would be written in binary as: a. 011 101 001. c. 011 111 101. b. 001 101 011. d. 010 100 011. 54. The hexadecimal number 2D9 would be written in binary as: a. 0010 1101 1001. c. 1100 1111 0010. b. 1001 1011 0010. d. 0010 1011 1001. 55. One byte of the data shown is represented by: a. No. 1 c. No. 3 b. No. 2 d. No. 4 56. A is an example of an actuator that could be controlled by a discrete output from a PLC. a. pushbutton c. limit switch b. motor starter d. all of these 57. A/An input or output is a continuously variable signal within a designated range. a. discrete c. BCD b. digital d. analog 58. Which of the following input field devices would most likely be used with an analog interface input module? a. Pushbutton c. Selector switch b. Limit switch d. Thermocouple 8
Name: 59. The schematic diagram shown is that of a(n): a. discrete output module. c. discrete input module. b. analog output module. d. analog input module. 60. The purpose of the filter section is to: a. aid in fault diagnosis. b. set the minimum level of voltage that can be detected. c. protect against electrical noise interference. d. separate the higher line voltage from the logic circuits. 9
Name: 61. The purpose of the zener diode (Z D ) is to: a. aid in fault diagnosis. b. set the minimum level of voltage that can be detected. c. protect against electrical noise interference. d. separate the higher line voltage from the logic circuits. 62. High-density I/O modules: a. may have up to 64 inputs or outputs per module. b. require more space. c. can handle greater amounts of current per output. d. all of the above. 63. Discrete I/O modules can be classified as: a. bit oriented. c. processor oriented. b. word oriented. d. power supply oriented. 64. Batteries are used in a PLC's processor to a. maintain data in volatile memory when line power is removed from the processor. c. maintain data in nonvolatile memory when line power is removed from the processor. b. operate the status lights LEDs. d. maintain outputs through a power failure. 10
Name: 65. PLCs were originally designed as replacements for: a. microcomputers. c. analog controllers. b. relay control panels. d. digital controllers. 66. Which of the following is not an advantage that PLCs offer over the conventional relay-type of control system? a. Smaller size c. Higher current capacity b. Less expensive d. More reliable 67. The main difference between a PLC and relay control system is that: a. different types of input devices are used. b. different types of output devices are used. c. different input and output voltage levels are used. d. one uses hardwired relay control logic and the other uses programmed instructions. 68. The central processing unit: a. looks at the inputs, makes the decisions based on the program, and sets the outputs. b. looks at the outputs, makes the decisions based on the program, and sets the inputs. c. serves only to store the program in memory. d. serves only to supply power to the backplane. 69. The control plan stored in the PLC is called: a. a program. c. FORTRAN. b. a Boolean ladder. d. a microprocessor. 70. A human machine interface (HMI) a. allows the user to monitor a process. b. allows the user to control a process. c. can provide a graphical representation of a process. d. all of the above. 11
Name: 71. The voltage that would be present between the DC common and terminal 4 with the pushbutton closed would be approximately: a. 0 volts. c. 12 volts. b. 6 volts. d. 24 volts. 72. The devices connected to the terminals would be classified as: a. field input devices. c. field output devices. b. internal input instructions. d. internal output instructions 12
Name: 73. The diagram shown is that of a a. hardwired relay schematic. c. input module schematic. b. ladder logic program. d. output module schematic. 74. For there to be is a continuous logic path from left to right across the rung: a. I/1, 1/2, and 1/3 must all be at logic 1. b. I/1, 1/2, and 1/3 must all be at logic 0. c. I/1 and 1/2 or 1/3 must be at logic 1. d. I/1 and 1/2 or 1/3 will be at logic 0. Short Answer 75. Convert the binary number to a decimal number: 1111110 13
Name: 76. Convert the decimal number to a binary number: 20 77. Convert the Octal number to a binary number: 74 78. What is the 1s complement of 1001101? 79. Simplify, answer must be in binary. 100 +101 80. Simplify, answer must be in binary. 1101-0101 14
MECH 1500 Midterm Review Answer Section TRUE/FALSE 1. ANS: T PTS: 1 2. ANS: F PTS: 1 3. ANS: T PTS: 1 4. ANS: F PTS: 1 5. ANS: T PTS: 1 6. ANS: F PTS: 1 7. ANS: T PTS: 1 8. ANS: F PTS: 1 9. ANS: F PTS: 1 10. ANS: T PTS: 1 11. ANS: T PTS: 1 12. ANS: T PTS: 1 13. ANS: T PTS: 1 14. ANS: F PTS: 1 15. ANS: T PTS: 1 16. ANS: T PTS: 1 17. ANS: T PTS: 1 18. ANS: F PTS: 1 19. ANS: T PTS: 1 20. ANS: T PTS: 1 21. ANS: T PTS: 1 22. ANS: T PTS: 1 23. ANS: F PTS: 1 24. ANS: T PTS: 1 25. ANS: T PTS: 1 26. ANS: T PTS: 1 27. ANS: T PTS: 1 28. ANS: F PTS: 1 29. ANS: T PTS: 1 30. ANS: T PTS: 1 31. ANS: T PTS: 1 32. ANS: T PTS: 1 33. ANS: T PTS: 1 34. ANS: T PTS: 1 MULTIPLE CHOICE 35. ANS: C PTS: 1 36. ANS: A PTS: 1 37. ANS: A PTS: 1 1
38. ANS: D PTS: 1 39. ANS: B PTS: 1 40. ANS: A PTS: 1 41. ANS: A PTS: 1 42. ANS: B PTS: 1 43. ANS: C PTS: 1 44. ANS: D PTS: 1 45. ANS: A PTS: 1 46. ANS: D PTS: 1 47. ANS: B PTS: 1 48. ANS: C PTS: 1 49. ANS: B PTS: 1 50. ANS: B PTS: 1 51. ANS: B PTS: 1 52. ANS: B PTS: 1 53. ANS: B PTS: 1 54. ANS: A PTS: 1 55. ANS: A PTS: 1 56. ANS: B PTS: 1 57. ANS: D PTS: 1 58. ANS: D PTS: 1 59. ANS: C PTS: 1 60. ANS: C PTS: 1 61. ANS: B PTS: 1 62. ANS: A PTS: 1 63. ANS: A PTS: 1 64. ANS: A PTS: 1 65. ANS: B PTS: 1 66. ANS: C PTS: 1 67. ANS: D PTS: 1 68. ANS: A PTS: 1 69. ANS: A PTS: 1 70. ANS: D PTS: 1 71. ANS: D PTS: 1 72. ANS: A PTS: 1 73. ANS: A PTS: 1 74. ANS: C PTS: 1 SHORT ANSWER 75. ANS: 126 PTS: 1 2
76. ANS: 10100 PTS: 1 77. ANS: 111100 PTS: 1 78. ANS: 0110010 PTS: 1 79. ANS: 1001 PTS: 1 80. ANS: 1000 PTS: 1 3