What Is a Stopwatch?
A stopwatch is a measuring instrument used to measure time during various experiments or evaluations. It typically measures time from 0 seconds to 60 minutes in 1/100th of a second increments.
Standard features include a start button to begin timing, a stop button to end timing, and a reset button to clear the recorded time. The timer increments when the start button is pressed or counts down from a preset time, emitting an audible alarm when reaching 0 seconds. Some models also have a dial knob for easy time setting.
Uses of Stop Watches
Stopwatches are essential in troubleshooting, for instance, in product design. If a defect is known to occur within a specific period under certain conditions, accurately measuring this duration is crucial. Typically, the defect’s duration is measured by manually starting and stopping the watch, which may not be highly accurate. However, repeating the measurement several times and taking the average can provide reasonably accurate data. This method can identify delay times in circuits or response times, aiding in pinpointing the defective circuit part.
Principles of Stop Watches
A stopwatch consists of a battery, quartz crystal, liquid crystal display, and a system on chip (SoC). The SoC divides the oscillation pulses of the quartz crystal, counts them, and displays the time on the liquid crystal display.
Pressing a button on the watch sends a signal to the SoC, which identifies whether it is a start, stop, or reset command. The start button initiates timing, the stop button ceases it, and the reset button clears the internal timing data. The core component, the crystal unit, generates an oscillation frequency when voltage is applied, determined by the crystal’s shape. Common oscillation frequencies range from several hundred KHz to a hundred MHz, with an accuracy about 0.001%, significantly higher than ceramic resonators. Although more expensive, these crystals ensure precise timekeeping. A 32.768 KHz crystal, divided to mark one-second intervals, is typically used for timing.