Exactime.nl> Stopwatches & Timers

As there are many different kinds of stopwatches, it is recommended that you devote a little time to making sure you choose the one most appropriate for your particular purpose. It is suggested that you decide first on the time division you need, then on the functions and thirdly on the kind of display ("analog" with hands as in mechanical models or "digital" as in quartz electronic).

Time division

You will need to take into account:
- the length of the times you will normally wish to measure (e.g. under or over 10-15 mins., 30 mins., or 1 hour)
- the degree of accuracy you will require (e.g. 1/5, 1/10 or 1/100 second)
- the kind of calculations you may have to make with the results

1/5 second

Recommended for timing events in which extreme accuracy is not required. If event lasts more than 30 mins., you should choose a model with a 0-60 minute (central) register. For timing events over 1 hour, choose a model which records hours too. This is the division most frequently used for timing in laboratories, research and those sports where the results are not required in fractions of a second. It is only available with analog display.

1/10 or 1/100 second

Recommended when greater accuracy than 1/5 second is required. For example: short and middle-distance track events (under 1500 m), swimming and precise scientific measurements. 1/10 is available only with analog display and 1/100 both with digital and analog display. To decide between analog and digital, consult section headed "analog or digital display".

1/100 minute (decimal minute)

Recommended for industrial timing in which the minute is divided into 100 parts to facilitate the analysis of results and the conversion into cost and production-time averages. Available with both analog and digital display.

Functions

Most stopwatches are used to time one single uninterrupted event. For this purpose the simplest model of stopwatch is all you need: one with 1 crown and no side buttons. However, as it is sometimes necessary to measure more than just the duration of one uninterrupted event, there are stopwatches with a number of other functions.

Basic version

Recommended for all simple time measurements. The single crown is used to start, stop and return the hands to zero as well as wind the mechanism.

Time-out and safety-reset

If you wish, for example, to measure the time in which an event takes place including interruptions, a stopwatch with a time-out function will enable you to start the hands, stop them at the beginning of an interruption and restart them simply by pressing the crown. Known as safety reset or locked return, the hands can only be returned to zero if the stopwatch is first stopped, so that the timing is not affected by any accidental pressure on the side button. Standard for most analog stopwatches.

Time-out and fly-back return

Recommended for measuring successive cycles in time study or laboratory tests. As soon as one cycle has been completed and the time read off, a pressure on the side-button will send the hands back to zero from where they will start running again instantaneously as soon as the button is released. On some models the crown will activate the fly-back and instant restart feature, whereas a silent side-slide starts and stops the movement.

Split action

This is a typical function of a digital stopwatch and is used to "freeze" the display for a moment in order to read an intermediate time; internally the stopwatch goes on to measure the overall time for the event. Also available in mechanical models: the red hand is running together with the regular hand, this split-hand is stopped by depressing the pushbutton to read the time and will catch up to the regular hand by depressing the pushbutton again.

Lap action

It is used, for instance when timing a car in an automobile race. The unit it set in motion at the start and when the car completes a lap, the net laptime is recorded and simultaneously the timing of the next lap starts.

Analog or digital display

Analog (with hands) stopwatches are mechanical and are recommended:
- for timing sports events in which the results are not required in fractions of seconds
- for timing all events or activities in which the time still available (remaining) needs to be ascertained quickly (for instance when refereeing a football match, recording a TV program or carrying out a given number of exercises within a set length of time)
- for those who are timing in extremes of temperatures (-10°C or + 50°C)
- when batteries are difficult to obtain
Digital (with numbers) stopwatches are electronic. They use a quartz crystal and are recommended:
- when accuracy requirements are particular stringent
- when it is vital to avoid all risk of human error in reading the time
- when times to 1/100 second are required (for instance in short distance track races as 100-400 m)
- when split, lap or memory functions are required for timing races as in competitive swimming