There are several different kinds of timers in use today. Basically, a timer is a special sort of clock. It keeps track of time as it counts down from a particular time interval. So, in other words, a timer differs from a stopwatch in the way that it counts.
A stopwatch starts at one second and goes up, while a timer might start at ten minutes and count down. You would use a stopwatch to time an Olympic runner, while you would use a timer to cook an egg that needs to be on the stove for 3 minutes.
Following are the primary different types of timers:
The first type of timer is the mechanical timer. These types are inexpensive and usually use a flat beater that spins against air resistance for operation. Some of them are more sensitive, and are built more like an alarm clock.
The second type of timer is the electrochemical timer. This type uses a thermal mechanism, and is usually used to measure intervals in things like Christmas lights and turn signals. These are commonly found around the home, and with home improvement projects.
The next type of timer is the electronic timer. These are basically quartz clocks that have special electronics inside of them. They are a lot more precise than mechanical timers, usually have digital displays, and are so inexpensive that they are now usually less expensive than mechanical timers. Plug-in timers fall into this category, as well as other types of personal electronic devices.
Computer times are the last type of timer that we will discuss. Computer timers are usually digital counters, and can be used to synchronize with certain computer functions or software. They can usually increment and decrement at a specific, set frequency, and this frequency is usually configurable. These types of timers are around you in everyday life, whether you realize it or not! The seemingly omnipresent in this day and age.
These are all of the major types of timers. One of the first types of timers was the hourglass; though the hourglass was very useful in its day, timers have come a long way since then!