Counters are used in applications that require items or products to be counted.

  • Counter instructions contain three words. The bits and words of counter instructions have addresses that can be used in the program of a PLC.
  • All counter instructions consist of three words: word 0, word 1, and word 2. Each word contains 16 bits.Word 0 contains five bits that are available for use in a PLC program:
    • bit 15—Count up (CU) enable
    • bit 14—Countdown (CD) enable
    • bit 13—done (DN)
    • bit 12—overflow (OV)
    • bit 11—underflow (UN)

Counter in PLC: Count up (CTU) instruction


  • A count up (CTU) instruction is a PLC programming instruction used to count the number of operations or products produced by a system.
  • A CTU instruction counts up on every false to true transition of the logic preceding the instruction on a rung.
  • The accumulated value of a CTU instruction increases by one for every false to true transition.
  • A CTU instruction will allow a counter to continue to count past the preset value. An identically addressed RES instruction is required to reset a CTU instruction.

Counter in PLC : Countdown(CTD) instruction


  • When used together, CTD and CTU instructions have the same address, similar to OTL and OTU instructions.
  • CTU and CTD instructions share the same status bits, preset values, and accumulated values. However, each counting instruction has its own logic.
  • A CTD instruction counts down on every false to true transition of the logic preceding the instruction on a rung.
  • The accumulated value of a CTD instruction decreases by one for every false to true transition of the logic preceding a CTD instruction on a rung. Conversely
  • A CTU instruction causes the accumulated value of a CTD instruction to increase. A single identically addressed RES instruction is required to reset CTD and CTU instructions.here below image show CTD instruction and related bit


 

3 COMMENTS

    • Thanks, Suraj For Your Comment. Actually, we explain common timer operation of all plc, so anyone can understand basics operation, But as per your request
      we are send you detail on your mail id.

    • Thanks, Suraj For Your Comment. Actually, we explain common timer operation of all plc, so anyone can understand basics operation, But as per your request
      we send you detail on your mail id.

LEAVE A REPLY

Please enter your comment!
Please enter your name here