The evolution of elapsed time indicators

People have always been interested in the passage of time, and methods to observe and record time, go back hundreds of years. Observation of the celestial bodies – the sun, the moon and the stars – was the first method used to measure time. Gradually, more sophisticated methods of depicting time and passage of time have evolved. The oldest of these devices is probably the sundial. Interestingly, some could also be used as a moon dial (such as the 17th Century one at Queen’s College, in Cambridge, England).

Other examples of large communal devices for telling time, and therefore acknowledging the passage of time, are clock towers, church bells, noon-day cannons, and the time ball. The primary purpose of the ancient carved stone obelisk was as a monument to commemorate a person or an event, but its long, tall, needle-like shadows could be used to show the passage of time using points on the ground.

On a smaller and more personal level, various types of simple clocks that relied on the movement of different substances, were invented and utilised. These included the water clock, candle clock, incense clock and hourglass and even a pocket-model sundial came into being. The courting candle is an especially interesting example of a device used to show the passage of time. Used in the 1600s to the 1800s by the father of a young girl to control the amount of time a suitor could spend courting his daughter. The father could lengthen or shorten the ‘courting time’ by providing a long or a short candle, according to his opinion of the suitor! Perhaps you have heard of the South African version, the opsitkers?

Time indicators have evolved from simple visual or audible indicators of the passage of time, to devices which are now either mechanical, analogue, chemical or electronic indicators, some of which can indicate accumulative time (such as the running time of an engine) in addition to the passage of time.

A coulometer is an analogue elapsed time indicator (ETI) which uses an electro-chemical plating process to integrate current over time. According to the manufacturer, Curtis Instruments, devices of this nature were used by NASA (National Aeronautics and Space Administration) in the Apollo Project to monitor all major electronic systems.

A research and development company in North Carolina, USA, has developed a device that allows users to monitor machines, motors and other expensive equipment remotely via the web. It allows them to check run hours and maintenance schedules remotely. In addition, the system can send e-mail alerts for real-time notifications.


ETIs can be used in many industries to improve efficiency, productivity, safety, and ultimately profitability, by enabling the following:

• Timely replacement of moving parts in machinery
• Timely replacement of filtering equipment (e.g. water filters)
• Timely servicing of equipment e.g. lifts, vending machines
• As a warning of impending expiry of warranties

As in the days of old, our interest in the passage of time, continues today, where elapsed time indicators (ETI’s) have found themselves a firm place across all industries in which total quality management (TQM) is a key objective.

We are proud to be the preferred supplier in Southern Africa of Timestrip UK (Pty) Ltd, who manufacture cost effective, elapsed time indicators. Contact us to find out more about this offering and how it can help your business.