Introduction to Industrial Automation

2.3.6   Counters and Hour Meters

In many industrial applications, it is necessary to count pulse-type events such as strokes, rotations, 

“product passing”, ON-OFF changes of devices, etc. The simplest way to achieve this is to use an 

electromechanical counter, like the one shown in Figure 2.65a. Counting only has an indication 

purpose, unlike counting-value processing. Conventional automation systems are unable to pro-

cess counting values. However, in the case of PLCs that contain many digital counters, it is pos-

sible to both indicate and process counting values. Electromechanical counters are often referred 

as “totalizing” counters, since they display a total quantity. For example, in counting bottles, the 

(a)

(b)

Figure 2.64  Solenoid actuators for current breaker operation, shunt trip coil (a) and under-