Here is a little history about an Elapsed Time Meter. It was first described by Marcus Vitruvius Pollio, he was a Roman Author Architect, Civil Engineer and Military Engineer during 1st century BC around 27 and 23 BC. It is believed that the actual Inventor may have been Archimides of Syracuse (c.287 BC-c. 212 BC) It was based on the Chariot Wheels Turning 400 times in one Roman Mile. Each Revolution a pin on the axle engage 400 tooth cogwheel, thus turning it in one complete revolution per mile. This engaged another gear with holes along the circumference where pebbles were located that were to drop one by one into a box. The distance traveled would this be given simply by counting the number of pebbles.
The odometer was also independently invented in ancient China possibly by the profuse Inventor and early scientist Zhang Heng (78 AD-129 AD) of the Han Dynasty (202 BC-220 AD)
The purpose of an Elapsed Time Meter it tracks the hours of a pump operations. One purpose is the ability to determine when preventative maintenance of the pumps is required. A second purpose is to calculate the volume of flow which has passed through the treatment system.
We also use Electronic timers which are essentially quartz clocks with special electronics, and can achieve higher precision than mechanical timers. Electronic timers have digital electronics, but may have an analog or digital display. Integrated circuits have made digital logic so inexpensive that an electronic timer is now less expensive than many mechanical and electromechanical timers. Individual timers are implemented as a simple single-chip computer system, similar to a watch and usually using the same, mass-produced, technology.
Many timers are now implemented in software. Modern controllers use a programmable logic controller (PLC) rather than a box full of electromechanical parts. The logic is usually designed as if it were relays, using a special computer language called ladder logic. In PLCs, timers are usually simulated by the software built into the controller.