Timers: Choose and Use Guide

There are a number of different timers and stopwatches available, each with a unique function or combination of functions. Besides the obvious categories of mechanical (spring wound or motor driven) and digital (crystal time-based circuitry), there are four main functions that our timers can be said to perform:

Count up (elapsed time):
Typically a stopwatch function that answers the question, "How long did that take?" Starting from zero, the timer is initialized at the beginning of an event, and then stopped when the event is finished. The reading on the timer is the elapsed time, and represents the duration of the event. The advantage of using a count up stopwatch instead of a standard watch or clock is that the stopwatch (or timer) can be set to zero, eliminating the need to manually subtract the start time from the finish time to calculate the elapsed time. Also, most stopwatches will give elapsed time in increments of 1/100 of a second, far greater than a watch or clock.

Count down:
Useful when you want to perform a task for a known, preset duration. Cooking is a common example; rice cooks for fifteen minutes, etc. You would program the duration into the timer, and it would count down and then alarm when the timer reaches zero. Most count down timers can be set in increments down to one full second.

Clock:
A clock is a device that tells the time. In addition to our Wall Clock, many of our stopwatches and timers also feature built in clocks, and some stopwatches even have alarm clocks.

Mechanical control:
Can be accomplished using a timer that switches an AC outlet. This can be used to turn a dosing pump on and off, to control lighting for a hydroponics experiment, and many other applications. The older mechanical timers use a rotary dial with "trippers" that can be set in fifteen-minute increments, up to four on/off operations every 24 hours. The digital version allows up to six on and six off switches every 24 hours, and specific configurations can be set to a particular day of the week, or to groupings of days, such and Monday through Friday, or Saturday and Sunday.