Everyone knows what a stopclock or stopwatch is, however many different varieties area available for use in the science classroom and prices and specifications vary greatly. The stopclock you choose to but will depend on your specific requirements.
Analogue stopclocks and watches have been used for many years in schools. They consist of two moving hands, one takes an hour and one a minute to complete a full sweep.
Digital stopclocks and stopwatches are obviously more accurate and usually have two buttons; reset which resets the display to zero and start/stop which with the first press starts the timer and with the second pauses it.
Some types of stopclock have jack sockets which allow the counter to be started and stopped using an external switch. This can have benefits in physics for example when an external push switch could be depressed by a moving trolley.
Analogue stopwatches can be damaged if dropped and other digital stopclocks vary in their robustness. Many schools purchase desk mounted stopclocks for use in the classroom and smaller, more robust stopwatches for field work.
Batteries are another consideration when choosing stopclocks. Smaller stopwatches tend to use watch type disk batteries which are relatively expensive although can be bought cheaply in bulk from companies such as Rapid.
Desktop clocks may take 'AA' or 'AAA' type batteries. Most do not have on/off switches and so are always on. In any case if they incorporate a standard LCD display, battery life is very long.