PLC Counters

Introduction :

Counters track the number of events that take place in a process. Common applications of counters include counting the number of finished products that leave an assembly line, the number of defective parts and inventory tracking.

There are two basic types of counters namely: 

UP Counter

DOWN counter 

which are available with every PLC manufacturer. The other 2 counters are such which are made available or not made available by few manufacturers, which are as follows: UP/ DOWN counter and HIGH SPEED Counters.

UP Counters: Counts from 0 up to the preset value, i.e. events are added until the number reaches the preset value. When the counter reaches the set value its contact change and done bit is set. Common applications of up counters are in assembly lines and packaging plants

DOWN Counters: Count down from the preset value to 0, i.e., events is subtracted from the set value. When the counter reaches the 0 value its contact change the state

UP-DOWN Counters: Combination of both up and down counter. These counters are commonly used to track inventory such as the number of products that enter and leave an assembly line. These counters also track defective parts

HIGH SPEED Counters: Count input pulses that are too fast separately from normal input points and modules. E.g. Input from turbine flow meter