1.Basically, the function of a PLC is to:

Transcription

1 1.Basically, the function of a PLC is to: a.amplify various weak signal sources. b.control a high voltage output with a low voltage input. c.control the speed of motors. d.make logical decisions and provide outputs. 2. The scan time is the time required a. to record the status of all input devices. b. to record the status of all output devices. c. to execute one cycle of the total program. d. for the information to pass from one circuit to another within the PLC 1

2 3. Unlike general purpose computers, PLCs are a. very expensive. b. harder to program. c. designed for the industrial environment. d. all of the above. 4. A programmed normally closed PLC contact with a bit status of 1 will not allow current to flow through the contact. is examined for an OFF condition. is examined for an ON condition. d. both a and b. 2

3 5. Parallel connections of a ladder logic program are typically called rungs. b.networks. coils. d.branches 6. The last element to be entered in a ladder logic rung is a(n): coil. b.contact. EXAMINE IF CLOSED. d.examine IF OPEN. 3

4 7. Which module of the PLC is responsible for performing logical operations? Processor Input Output d. Power supply 8. The status bit of switches and pushbuttons connected to a PLC is stored in the: input image table output image table file user program d. all of the above 4

5 9. In ladder logic programs, all outputs are represented by: contact symbols coil symbols schematic load devices d. branches 10. The addressing format used with PLCs: is always a five digit code is always represented using the octal number system is standard for all manufacturers d. none of these 5

6 11. A rung consists of: a. one or more inputs and only one output b. a series of inputs and a series of outputs c. NC or NO contacts. d. push-buttons or toggle switches 12.. Each complete horizontal line of a ladder logic diagram is generally referred to as rung branch input d. output 6

7 13. The abbreviations NO and NC represent the electrical state of switch contacts when: power is applied power is not applied the switch is actuated d. the switch is not actuated 14. A limit switch is usually actuated by: hand pressure contact with an object d. an electromagnet 7

8 15. Solenoid valves are available to control: oil flow air flow c. water flow d. all of these 16.. Field or real world devices refer to input devices only output devices only load devices only d. all devices that are physically wired to the PLC. 8

9 17. The three main components of PLCs are the input module, CPU, and a. actuator module b.. output module c.. operator interface d.. input device 18.. Prior to PLCs, many control tasks were solved with a. hard-wired controls b. actuator-sensor controls c. programmable-logic logic d. computer-controllers controllers 9

10 19.. A signal which varies continuously is called a. digital b. analog c.. continuous d. variable 20. The binary concept makes use of the fact that certain information a. can exist in one of two possible states b.. can be broken down into smaller units for easier analysis c.. can be divided into two or more categories d. can be divided into two, or multiple of two, categories 10

11 21. In conventional logic circuits, binary 1 represents a. the presence of a signal b. a high voltage level c. the occurrence of some event d. all the above 22. A single rung of a ladder logic program is arranged with a. Input conditions connected from left to right, with the output at the far right. b. Input conditions connected from right to left, with the output at the far left. c. The output in the center and the input conditions to the left and right of it. d. All input conditions in parallel and all output conditions in series. 11

12 23. Which of the following is not a factor in determining the total scan time of PLC? a. Memory protection. b. Program content. c. Program length. d. Total number of inputs and outputs used. 24. Programmed counters can: a. count up. b. count down. be combined to count up and down. d. all of these. 12

13 25. The PLC counter instruction is similar to the: a. internal relay instruction b. transitional contact instruction c. relay coil and contact instruction d. timer instruction 26. Unlike the TON timer, the RTO timer requires a(n): timer reset instruction. input condition instruction. internal relay instruction. d. instantaneous contact instruction. 13