Top Most Asked PLC DCS SCADA Questions In Interview

Q-1 what are the 5 main components of PLC?
Ans-1 : Power Supply, Processor, Memory, Input section & Output section

Q-2 what are the 4 main PLC programming languages?
Ans : Ladder Logic, Function Block Diagram, Structure Text & Sequential Flow Chart

Q-3 what is the purpose of PLC battery?
         Option (A) To provide the power to input section
         Option (B) To provide the power to output section
         Option (C) To provide the power necessary to retain the contents of CPU memory if power is removed from the PLC.
         Option (D) None of above
Ans : Option C

Q-4 How many types of memory in PLC?
          Option (A) RAM & ROM Memory
          Option (B) Volatile & Non-volatile Memory
          Option (C) All of the above
          Option (D) None of above
Ans : Option C

Q-5 How many data files are already created by default in rslogix500 programming software?
          Option (A) From 0 to 8
          Option (B) From 1 to 9
          Option (C) From 9 to 255
          Option (D) None of above
Ans : Option A

Q-6 what is NO in PLC?
          Option (A) normally opened
          Option (B) If examine if close
          Option (C) If the corresponding memory bit is a “1” (on), this instruction will allow rung continuity and outputs will be energized
          Option (D) All of the above
Ans : Option D

Q-7 what is NC in PLC?
          Option (A) normally closed
          Option (B) If examine if Open
          Option (C) If the corresponding memory bit is a “1” (on), this instruction will not allow rung continuity and outputs will be de-energized.
          Option (D) All of the above
Ans : Option D

Q-8 what is OTE (output Energize coil) in PLC?
          Option (A) This instruction set the specified bit, when rung continuity is achieved
          Option (B) This instruction set the specified bit, when input condition goes true.
          Option (C) All of the above
          Option (D) None of above
Ans : Option C

Q-9 How to do sinking type wiring of a push button in PLC?
          Option (A)     
         
          Option (B) 
         
          Option (C) All of the above
          Option (D) None of above
Ans : Option A

Q-10 what is sinking type wiring in PLC?
          Option (A) Sinking input module will have the current flowing into it
          Option (B) In sinking type wiring: the input sensing device will connect with the voltage and common connect with no-voltage.
          Option (C) Sinking input module will have the current flowing out of it
          Option (D) A and B is correct
          Option (E) B and C is correct
Ans : Option D

Q-11 what is sourcing type wiring in PLC?
          Option (A) Sourcing input module will have the current flowing into it.
          Option (B) In sourcing type wiring: the input sensing device will connect with the No voltage and common connect with voltage
          Option (C) A Sourcing input module will have the current flowing out of it.
          Option (D) A and B is correct
          Option (E) B and C is correct
Ans : Option E

Q-12 which software is used for programming Allen Bradley MicroLogix PLC?
          Option (A) CCW
          Option (B) RSLogix5
          Option (C) RSLogix500
          Option (D) SIMATIC STEP 7
Ans : Option C

Q-13 what is upload and Download in PLC?
          Option (A) Upload means transfer program from Computer to PLC and download means transfer program from PLC to Computer
          Option (B) Upload means transfer program from PLC to Computer and download means transfer program from PLC to Computer.
          Option (C) All of the above
          Option (D) None of above
Ans : Option D

Q-14 what is OTL (Output Latch) in PLC?
          Option (A) This instruction set the specified bit, when input condition goes true & once a bit is set it is “latched” on. Once bit has been set “on” (1 in the memory) it will remain “on” even if the rung condition goes false
          Option (B) This instruction reset the specified bit, when input condition goes true & once a bit is reset, it is “Unlatched”. Once bit has been reset “off” (0 in the memory) it will remain “off” even if the rung condition goes false.
          Option (C) All of the above
          Option (D) None of above
Ans : Option A

Q-15 what is OTU (Output Unlatch) in ladder logic
          Option (A) This instruction set the specified bit, when input condition goes true & once a bit is set it is “latched” on. Once bit has been set “on” (1 in the memory) it will remain “on” even if the rung condition goes false
          Option (B) This instruction reset the specified bit, when input condition goes true & once a bit is reset, it is “Unlatched”. Once bit has been reset “off” (0 in the memory) it will remain “off” even if the rung condition goes false.
          Option (C) All of the above
          Option (D) None of above
Ans : Option B