Description

Electromechanical counters are used to detect, totalize, and indicate a sequence of events. They typically accept electric or electronic inputs to operate mechanical outputs such as rotating wheels or knobs. These devices may count UP and/or DOWN, support multiple functions, and provide reset capabilities

Electromechanical counters are often used on assembly lines or in manufacturing applications. For example, a device that counts the number of units filled from a hopper may be part of a larger system that determines when the hopper needs to be refilled.  Unlike electronic counters, however, most electromechanical devices  do not display data with LEDs or LCDs.

Types

There are four basic categories of electromechanical counters: devices that accumulate counts (counters), devices that accumulate counts and control equipment (presets and totalizers), position indicators, and counter/timer combinations. 

The GlobalSpec SpecSearch database contains products in each of these categories, and further divides them into the following types.

• Batch counters count in one direction only – UP.  Typically, they can be pre-set so that when the required number of batches or pieces is complete, the process stops automatically.
• Event counters are designed to count the occurrences of a specific condition or event, such as lightning strikes or machine shutdowns.
• Frequency counters are used to display frequency, the number of cycles per second of a waveform, in Hertz (Hz). Typically, they are used as test equipment in the electronics industry.
• Pulse counters are designed to count a momentary but sharp change in current and voltage. Because pulses are digital signals, the voltage or current is either ON or OFF.
• Preset counters can control an external circuit when the counted total matches user-entered preset limits. Typically, counting is subtractive (DOWN) in preset mode.
• Count totalizers both accumulate counts and control machines. They can track counts over relatively long periods of time and are often pre-settable.   
• Position indicators can accept, process and/or display angle or travel data.  They may be used with encoders, valves, and pneumatically-operated linear actuators.

Specifications and Features

Electromechanical counters may have multiple analog and/or digital input channels and accept signal, sensor, or specialized inputs. Available outputs include voltage, current, frequency, and serial or parallel outputs. The user interface is also important to consider, especially in low-light or noisy environments. Some electromechanical timers are equipped with an explosion-proof housing or have audible or visual alarms. 

References

https://www.electronics-notes.com/info/t_and_m/frequency_counter/counter_basics.php