Chronograph Watches: What is it & How Does It Work?

What is a Chronograph Watch?

A chronograph is essentially a stopwatch integrated into a watch or timepiece. It allows the measurement of elapsed time with precision. The term “chronograph” is often used interchangeably with “stopwatch” because both refer to devices used for timing events.

A chronograph typically has a central seconds hand that can be started, stopped, and reset using push-buttons or pushers on the watch’s case. In addition to the central seconds hand, there are usually sub-dials on the watch face that measure minutes and hours. These sub-dials enable the tracking of longer durations, providing additional functionality beyond a basic stopwatch.

Chronographs are commonly used in various fields and activities, including sports, aviation, motorsports, and scientific experiments, where accurate timing is crucial. The ability to measure and record elapsed time with precision makes chronographs versatile tools in many applications.

How Does it work?

Operating a chronograph watch can vary slightly depending on the specific model and brand, but here are the general steps to operate a chronograph:

1. Start the chronograph: To start the chronograph, press the top push-button. The central seconds hand should begin moving, indicating that the chronograph is in operation.

2. Stop the chronograph: To stop the chronograph and record the elapsed time, press the top push-button again. The central seconds hand will halt, and you can note the elapsed time on the corresponding sub-dial.

3. Reset the chronograph: To reset the chronograph back to zero, press the bottom push-button. This action will return all the chronograph hands—seconds, minutes, and hours—to their starting positions.

4. Use the additional sub-dials: The sub-dials on the watch face indicate the elapsed time in minutes and hours. The seconds sub-dial usually corresponds to the central seconds hand. The sub-dials may have small hands or rotating discs to track the elapsed time.

5. Measure longer durations: If you need to measure durations longer than a minute, use the minutes or hours sub-dials. The minutes sub-dial often tracks up to 30 or 60 minutes, while the hours sub-dial can measure longer periods.

A chronograph watch may also be accompanied by a bezel, which is a ring that surrounds the watch face. Bezels on chronograph watches serve various functions and can add additional features and capabilities. Here are some common types of bezels found on chronograph watches:

1. Tachymeter bezel: A tachymeter bezel is often found on chronographs and allows the wearer to measure speed over a known distance. The bezel is typically marked with a scale that enables the calculation of speed based on the time taken to cover a specific distance.

To use the tachymeter scale on a watch, follow these steps:

• Determine the purpose: Decide whether you want to measure speed or distance using the tachymeter scale.
• Start the stopwatch: Start the stopwatch as the event begins.
• Measure the elapsed time: Allow the event to proceed, and stop the stopwatch when the event ends. Take note of the elapsed time in seconds.
• Read the tachymeter scale: Look for the tachymeter scale. It is typically marked from 60 to 400 or higher, and it may be labeled with units such as kilometers per hour (km/h) or miles per hour (mph).
• Find the corresponding value: Locate the point on the tachymeter scale that aligns with the elapsed time you measured on the stopwatch. This point represents the speed or distance based on the chosen unit of measurement.
• Interpret the result: Depending on whether you’re measuring speed or distance, you can use the tachymeter scale value to calculate the corresponding quantity.
• For measuring speed: If the tachymeter scale is labeled with kilometers per hour (km/h), and the point aligns with the elapsed time of 20 seconds, it means the speed is 180 km/h. Adjust the calculation if the scale is labeled differently.
• For measuring distance: If you want to measure the distance traveled, you’ll need to know the time taken and the speed. Use the formula distance = speed × time to calculate the distance.

Remember to consider the unit of measurement used on the tachymeter scale and adjust your calculations accordingly.

It’s important to note that tachymeter scales are typically designed for measuring events that last less than a minute. For longer events, the accuracy of the tachymeter scale may decrease, and alternative methods or devices may be more appropriate for accurate measurements.

2. Telemeter bezel: A telemeter bezel is a feature found on some watches that allows you to measure the distance between you and a visible event based on the speed of sound. It is typically marked with a scale on the outer edge of the watch dial.

Here’s how you can use a telemeter bezel:

• Identify the event: Determine the event you want to measure the distance to. It could be a visible occurrence that produces both a visual and audible effect, such as lightning and thunder.
• Start timing: When you see the event occur, start the stopwatch or note the time on your watch. This is the starting point of the measurement.
• Stop timing: As soon as you hear the sound associated with the event (e.g., the thunderclap following a lightning strike), stop the stopwatch or note the time on your watch. This is the ending point of the measurement.
• Calculate the distance: To calculate the distance to the event, you need to know the speed of sound, as it is a constant. The speed of sound is approximately 343 meters per second (or 1,125 feet per second) at standard atmospheric conditions.

If you’re using the metric system, multiply the time elapsed (in seconds) between the event’s visual occurrence and the sound reaching you by 343 to obtain the approximate distance in meters.

If you’re using the imperial system, multiply the time elapsed (in seconds) between the event’s visual occurrence and the sound reaching you by 1,125 to obtain the approximate distance in feet.

Adjust for echo or other factors (optional): If there are echoes or other factors that may affect the accuracy of the measurement, you can make adjustments accordingly. For example, if you hear an echo, you may need to consider that the sound traveled to and from the event, so you would divide the calculated distance by 2 to get the actual distance to the event.

It’s important to note that the telemeter bezel is a rough approximation and works best for relatively close events. Additionally, factors such as atmospheric conditions, temperature, and background noise can affect the accuracy of the measurement. Therefore, the telemeter bezel should be used as a general guideline rather than a precise measurement tool.  

3. Slide rule bezel: Certain chronographs, particularly those designed for aviation or scientific calculations, may feature a slide rule bezel. The slide rule is a mechanical computational tool that can perform various mathematical calculations, such as multiplication, division, unit conversion, and more. By rotating the bezel, users can align different values and perform calculations using the slide rule.

Here’s how to use a slide rule bezel:

• Familiarize yourself with the bezel: The slide rule bezel consists of two rotating scales, an outer and an inner scale. The outer scale is fixed, while the inner scale can be rotated.
• Understand the scales: The scales on the bezel are typically logarithmic and marked with various numbers, symbols, and units. Different models may have different scales, so refer to your watch’s manual to understand the specific markings on your bezel.
• Determine the calculation: Decide which type of calculation you want to perform using the slide rule bezel. The most common calculations include multiplication, division, and unit conversion.
• Align the values: For multiplication or division, align the desired numbers on the outer scale with the corresponding numbers on the inner scale. For example, to multiply 2 by 3, you would align the number 2 on the outer scale with the number 3 on the inner scale.
• Read the result: Look at the value on the inner scale aligned with the other number on the outer scale. This will give you the result of the multiplication or division calculation. Make sure to account for any decimal places or significant figures based on the scale and markings.
• Perform unit conversions: Some slide rule bezels have additional markings for unit conversions. To convert between units, align the starting value on the outer scale with the corresponding conversion factor on the inner scale. Then, read the converted value on the inner scale aligned with the desired unit on the outer scale.
• Practice and refer to the manual: Using a slide rule bezel may require practice and familiarity with the specific markings and scales on your watch. Consult your watch’s manual for detailed instructions and examples specific to your model.

Note that slide rule bezels can be quite complex, and mastering their usage may take time and practice. It’s advisable to refer to the manual and seek additional resources or tutorials to gain a thorough understanding of how to use the slide rule bezel on your particular watch model.

4. Dive bezel: In diver’s chronograph watches, the bezel is often unidirectional and used for timing dives. It typically rotates only counterclockwise to prevent accidental adjustments that could shorten the dive time. The bezel is marked with elapsed time in minutes and is used in conjunction with the chronograph to track the time spent underwater.

Here’s how to use a dive bezel:

• Set the starting position: Before entering the water, make sure the bezel is set to the starting position. The starting position is usually aligned with the 12 o’clock mark on the watch dial.
• Align the bezel with the minute hand: To measure elapsed time, rotate the bezel so that the current minute hand lines up with the zero mark on the bezel. Ensure the bezel rotates in the counterclockwise direction only, preventing accidental movement that could shorten the measured time.
• Start your dive: Once you begin your dive or any timed activity, such as underwater exploration or decompression stops, note the position of the minute hand on the bezel. This indicates your starting time.
• Track elapsed time: As time progresses, the minute hand on your watch will move along the dial. To measure elapsed time, observe the position of the minute hand relative to the bezel. The number on the bezel that aligns with the minute hand represents the elapsed time in minutes.
• Monitor remaining dive time: The bezel also helps you monitor your remaining dive time and calculate safe ascent times. As you progress through your dive, take note of your remaining available dive time by aligning the minute hand with the corresponding number on the bezel.
• Be aware of safety margins: Dive bezels often include markers or indicators to denote specific time intervals, such as decompression stops or no-decompression limits. These markers help divers adhere to safety guidelines and avoid exceeding time limits.

It’s important to note that dive bezels are a useful tool for tracking elapsed time during dives, but they should not be relied upon as the sole means of timekeeping. Divers should also use a reliable dive computer or dive watch with additional timing and depth measurement features to ensure accurate and safe dive profiles. Regular maintenance and calibration of your dive watch are essential to ensure its accuracy and functionality.

These are just a few examples of bezels commonly found on chronograph watches. The specific functionality and markings on the bezel may vary depending on the watch model and it’s intended