About the dial of a chronograph watch -2-

Introducing the functions of chronograph watches


Soon the accuracy of simply dividing the time into 1/5th of a second became unsatisfactory and later a mathematical method was required to measure all events. So a scale/ruler was developed that could be read visually without the need for complicated mathematical procedures.

The most common thing we see is a scale that allows us to measure distance in kilometers (km) under certain conditions.

On or near the dial, there is a scale marked in kilometers, and the word "TELEMETER" is written. The first "tele" means distance, and when combined with "meter", it means "something that measures distance". Distance is measured based on the speed at which sound travels through the air.

For example, if you see lightning far away, you can measure the time it takes to actually hear the sound of thunder. Multiplying this time by the speed of light, which is 333 m/s, will give you the distance to the lightning.

In 1892, Theodore Schaedeli of La Chaux-de-Founds patented a pocket chronograph capable of measuring distances to an accuracy of 51 metres (m). Distance was measured by pointing the 30-second chronograph hand directly onto the fine graduations in metres (Z14). The graduations printed were based on a temperature of 16°C, where the speed of sound is 340.67 m/s. Schaedeli also included corrections to allow distance measurements at other temperatures.

This is how the measured distance is modified depending on the temperature.

Temperature 20°C +0.50m/100m

Temperature 16 degrees +0.00m/100m *Speed ​​of sound 340.67m/s

Temperature 10 degrees -0.56m/100m

Temperature 5 degrees -1.50m/100m

Temperature 0 degrees -3.00m/100m

The distance that sound travels in one second at a temperature of 20 degrees is calculated as 340.67m + (3.467 x 0.5)m = 342.37m, which is 342.37m. On the other hand, at 0 degrees, it only travels 340.67m - (3.467 x 3)m = 330.47m. These corrections take into account the humidity of the air, but not the air pressure.

Most wristwatch chronographs, like the Z15, have a telemeter based on the speed of sound of 333.33 m/s. The dial is therefore scaled in increments of 0.1 to 0.5 km to allow accurate readings up to 20 km. The speed of sound of 333.33 m/s is the correction value for an environment with a temperature of approximately 5 to 10 degrees. Therefore, accurate distance measurements at normal temperatures of 20 to 30 degrees require the corrections already mentioned.

At normal atmospheric pressure of 760 Torr, the speed of sound (m/s) changes as follows:

-40 degrees 306.5m/s

-20 degrees 319.3m/s

-0 degrees 331.8m/s

+20 degrees 343.8m/s

+40 degrees 355.3m/s

+100 degrees 387.2m/s

The telemeter scale is usually located on the outermost edge of the dial.

It is written as "Telemeter" or "Telemetre" and often uses blue text.

The maximum readable distance (20km) is calculated as 333m/s x 60s = 19,980m or 20km, since it takes 60 seconds for the chronograph hand to complete one revolution.

Export watches are measured in miles. The dials of these watches are marked with the German word "Telemeile" or 12.62miles. This is because 1 mile is equal to 1609.3m, and the speed of sound is 333m/s=0.2069miles/s, which is 12.415 miles in 60 seconds.

The dial will show 12.625 or a number close to it, which already takes into account the correction factor: 12.625 miles is calculated from the speed of sound of 338.59 m/s at a temperature of 15 degrees.


The second scale commonly found on wristwatch chronograph dials is the tachymeter, which can be used for cars, cyclists, and pedestrians. The prefix tacho/tachy is also used for other terms that describe speed. From this scale, you can read the speed v of an object (v=s/t), where s is the distance and t is the time it takes to travel s. For short distances between 200m and 1000m, this can be read directly from the scale. For example, if a car travels 60km at a constant speed for one hour, then the speed is 60kph or 60,000m/3600s. A distance of 1000m takes 3600s/60=60s.

If you drive at twice the speed, 120km, in one hour, it takes 3600s/120=30s to travel 1000m. On the tachymeter scale, you can easily read numbers such as 60, 80, 120kph, etc. (Z17).

Around 1900, Leon Guinand of the Swiss company Brenets obtained a patent for the tachymeter chronograph (No. 21709). This chronograph could display speeds directly on the dial, from 10 kph to 150 kph (Z16), allowing for a wide range of time measurements from short to long. Naturally, the chronograph hand had to complete one revolution in six minutes. As was customary at the time, the seconds hand was graduated every second, not every fifth of a second, which would have been very inconvenient. Modern tachymeter chronographs can read off speeds directly from the scale, from 60 kph to 1000 kph.

In 1907, F. Amez-Droz of Geneva patented the so-called "snail tachymeter" (Z18) with a spiral (no. 39276). It was used on pocket watches with dials on both sides of the front and back of the watch. The seconds hand completes one revolution in 2 minutes, making 5.5 revolutions in the spiral. The direction of the hand is counterclockwise because the tachymeter is on the back of the watch. The measurement range is 5 kph to 60 kph. This snail tachymeter was later widely used in wristwatch chronographs, so it was displayed on the front dial. Accordingly, the outermost scale was reduced in size from a maximum of 1000 kph to 60 kph (60 seconds = 1 revolution) and the spiral scale was reduced to 2 or 3 revolutions. This limited the measurement range to 20 or 15 kph.

Generally speaking, the scale of a tachymeter, or more precisely the maximum speed that can be read and marked on a tachymeter, reflects the era in which the chronograph was made. Wristwatch chronographs made in the 1920s are marked up to 300kph or 360kph, in the 1930s you will find 400kph, and around the 1940s you will find 500kph. By 1950, speeds had risen to 750-800kph, and by the mid-1950s, 1000kph. As the speeds of cars and planes increased, so did the measurable speeds. Advances in chronograph manufacturing not only changed the mechanism, but also the dial indications.

Naturally, readings from such small scales were less accurate than those from larger pocket watches made for them. Nevertheless, tachymeter chronographs could measure speeds over distances of up to 1000m, usually indicated by "BASE 1000" or "KM1000" printed on the scale. Some are also stated in miles for export purposes. Often telemeter and tachometer scales are displayed on the same dial, which looks very technical at first glance but is not particularly useful.

Pulse Meter

The third scale, often found on the dials of wristwatch chronographs, is called a "doctor's watch" and was used to measure the patient's heart rate. The heart rate is usually affected by the patient's health and illness. In the absence of a dedicated watch, the number of pulses is counted over a period of time (20 to 30 seconds) and the number of pulses per minute is calculated. Although not a particularly difficult calculation, the pulsometer (Z19) makes this task easier or even unnecessary. The dial is usually marked "Calcule sur 30 pulsations", "gradue pour une observation de 20 pulsations", or "Gradue pour 30 pulsation" (Z20). The numbers 20 and 30 indicate the number of pulses to be counted. Obviously, a person with a high heart rate will take less time to reach 20 or 30 beats than a person with a low heart rate.

This means that you press the start button on a chronograph with a pulsometer, measure the time it takes for 20 or 30 pulses, and the scale on the chronograph will tell you the number of beats per minute.

Breath-counting chronograph ( asmometer )

For athletes and doctors, it is important to measure respiration rate. To measure respiration rate, there are sometimes scales on the dial similar to a pulsometer. This allows you to measure the time it takes to take a few breaths (5 breaths) and read the number of breaths per minute from the dial.

The measurement range is usually between 60-14 and 40-10 breaths per minute, which are normal for human breathing rates. Often the dial has both a breath register and a pulse meter, since breathing rate and heart rate are often related.

Production Counting Chronograph

Industrialization led to the mass production of many different products. This was not only a result of increased demand, but also the need for practical production plans for mass production. To create these plans, the production times of each individual part had to be calculated and every step of the process had to be examined.

This is easy to do if you want to know the production time of just one part, say 30 minutes. But if several small parts are produced at the same time, either manually or automatically, each taking a minute, the exact time each one takes is no longer a simple calculation. In these situations, the production counting chronograph (Z21) is used.

The production counting scale serves to determine the production capacity of the individual parts in the production series. At the beginning of the production of a mass-produced part, a chronograph is started and stopped at the end of the production run. On the production counting scale, the chronograph hand indicates the number produced per hour, provided the measurement time is within 60 seconds. In the case of the Z22, the chronograph hand finally indicates 750 pieces, which means that 750 pieces of a particular part can be made per hour.

If the production time for one piece is about 1 second or less, it is better to use the total production time of several pieces in a row (for example, 10 pieces). In this case, the production volume per hour is 10 x 750 = 7500 pieces. If the production time for one piece is more than 60 seconds, for example, 80 seconds, then dividing 1 hour (3600 seconds) by 80 seconds gives you 45. This number means that you can produce 45 pieces per hour.

The dials are displayed in various ways. For the Z22 chronograph, the range is from 60 to 3000. For the Z23, the scale is from 60 to 1800, with an inner scale marked 30 to 59 for the second revolution of the chronograph hand. These chronographs are industrial and often have a decimal notation, e.g. 1 minute = 100 seconds, 1 hour = 100 minutes. Such notations are written next to the usual sexagesimal notation.

Telephone unit counter

In the past, especially for international calls, the system of paying the fee in 3-minute increments from the post office was the norm for a long time. It was very convenient for a chronograph minute counter to display every 3 minutes when making a call, in addition to the usual minute count. Generally, the first 3, 6, and 9 minutes were indicated by lines that extended longer than the other marks (Z24). This allowed you to see at a glance how much more time you had left to talk. Later, when the calculation method for telephone charges changed, this type of clock became unnecessary and was no longer seen on the face of a clock.

Telephone unit counter Z24

Tide Chronograph ( Yachting Chronograph )

The Z25 chronograph shows two different displays: the auxiliary minute counter dial X is divided into six areas of five minutes each, each colored: the darker areas are blue, the lighter areas are the color of the dial itself, silver.

In a regatta, the yachts are not allowed to cross the starting line until the second signal sounds exactly five minutes after the first signal. In the five minutes between these two signals, the yachts make the necessary preparations to start at the right time. The colored areas are an essential display for this chronograph.

The auxiliary dial on the left represents the water level (tides). It tells us when high and low tides occur in a particular port or coastline. Nowadays, the so-called tide tables for a particular coast are represented by pre-determined marks. To observe the continuous tides, clocks were made to give advance notice of the times of high and low tides.

The tide dial is a 24-hour ring with a rotating disk divided into four areas. On this disk, two axes (needles) cross. As shown in Z25, the top and bottom are blue, which represent high tide. The left and right areas are yellow, which represent low tide. The Y disk moves along the lunar orbit, and the cross indicates the tides. This cross does not cross at exactly 90 degrees, but the two points pointing to opposite positions have a difference of 12 hours and 25 minutes, which is the tidal cycle. The Z push button on the side of the case allows you to set the tides at a specific location or coast. This tide display is not related to the chronograph function at all, but is very useful in boating sports such as yachting.

Rotating Bezel: Time Setting and World Time

Setting rings, rotating panels and glass bezels are not uncommon in wristwatches. They not only indicate the time, but also serve to wind the watch and set the hands. In 1941, Philippe Weiss of La Chaux-de-Fonds patented a watch with a 12-hour scale printed on the setting ring, which served two purposes (patent no. 215450). The Z26 diagram was used in the patent application. The patent was granted for the setting ring being attached by a wave spring (Z26, fig. 2 and 3) and for the ring's function in conjunction with the times around the world (Z26, fig. 1). The chronograph is represented by a 30-minute minute counter dial. At the same time, the setting ring is marked with hour and half hour scales, so that it can also be used as an hour counter by setting the hour hand to the 12th number after the chronograph has been started.

As you can see in Z26 fig.1, the names of cities in each time zone are written around the fixed dial. The time difference between two cities located exactly opposite each other on the dial is exactly 12 hours. For example, Singapore and New York are exactly 12 hours apart, so when it is 12 noon in New York, it is 6pm in Berlin, and 12 midnight in Singapore. Therefore, if you want to know the time in Sydney, Australia, for example, you set the 12 on the setting ring to Azores or Sydney, and read the clock (hour) hand on the setting ring. In Z26 fig.1, the current time is almost 10:30, but it is about 7:30 in Sydney.

This system is not 24-hour, so determining whether it is AM or PM requires some geographical knowledge. If the area you are interested in is east of your current location, think in the direction of noon moving forward into night, whereas if it is west of your current location, think in the direction of noon moving backward into morning.

Rotating bezel: chronograph with calculator

Many measurements, such as telemeters, tachymeters, and production registers, are based on mathematical calculations and are displayed on a scale. However, this has the disadvantage that you must know the basics of the calculation (for example, the distance from the sound source to the speed of sound). Even in such cases, multiplication and division are possible if you use a logarithmic scale such as a sliding ruler.

Such a rotating logarithmic scale is attached to the opposite side of a fixed ruler, and this model was patented in 1941 by Graef & Cie. Fabrique MINO of La Chaux-de-Fonds, Switzerland (Patent No. 216202). Z27, figs. 1 to 3 reproduce the model at the time of the patent application. The patent was not for the logarithmic scale itself, but for a mechanical calculator already used by Jost Burgi (1552-1632) and J.Napier. The current push-button calculator was created by S.Partriges around 1662. The logarithmic ruler and rotating bezel are attached to a bezel fixed to the case, and the patent was granted for this method.

Figures 2 and 3 show the design sample when Graef & Cie applied for a patent. The setting ring 5 and glass plate 7 are attached to cover the case 14 and can rotate. One ruler is on the fixed dial 10, and the rotating ruler 6 is on the setting ring 5, so they are installed on the dial without any gap. As can be seen in Fig. 3, the surface of the dial 10 has a small step into which the ruler 13 of the setting ring 6 is fitted. The 1.0 to 9.9 logarithmic scale printed on the ruler 13 is protected from scratches and impacts by the glass plate 7.

By simply moving the ruler, you can read the scale accurately. This movable ruler can of course be used as a normal watch, but its usefulness is further enhanced when it is attached to a chronograph watch. A chronograph watch can measure small time intervals without losing track of the current time, so you can do calculations anywhere.

This watch can easily perform calculations related to exchange rates and increases/decreases in paper size (A4, B5, etc.). Calculator wristwatches were not widely used in the 1950s and 1960s, but pilots' aviation watches were equipped with calculation functions.

Chronograph with two crowns

Universal Perret and Berthoud Patents

All the functions of a watch cannot be operated by just two or three push buttons or one crown. Two companies came up with the idea of ​​adding a second crown at the same time and achieved success in a short time. Three patents were obtained by the Swiss company "Manufacture des Montres Universal Perret & Berthoud SA Geneve (Suisse)" on November 6, 1940 and September 22, 1941, and by the Swiss company "Excelsior Park, Le Fils de Jeannerer Brehm, St. ?Imier (Suisse)" on February 23, 1943. It is likely that Excelsior Park was aware of Universal Perret & Berthoud's new method and was looking for a similar method.

However, for Universal Perret & Berthoud to obtain a patent, they would have to invent a procedure different from those already patented, and of course there were ways to "circumvent" the patents that were already granted without breaking the law. It is noteworthy that the last patent was published on February 6, 1945, patent number 23507, and the other two were published on April 16, 1945, patent number 235608, and March 1, 1946, patent number 239879. As with ordinary watches, the method of placing the hands had already been developed, so there was nothing new and no longer a need for patent protection. The technique of attaching the second crown, as Universal Perret & Berthoud did, was designed to obtain a patent law. However, as is often the case, before it was published, their idea was circumvented by clever engineers who used the second crown for the same or similar purpose.

Universal Perret & Berthoud patented a function where the crown could be operated so that the seconds hand could act as a reminder (alarm function). These watches were named "Memento-Chronograph" by Ebauches SA and traded under this name. The Z28 fig.1 has the usual arrangement of hands for hours and minutes.

Additionally, below the 12 numbers there is a supplementary dial whose hands are operated by a second crown W (on the left side of the case) and move independently of the functioning of the watch. Once set, the hands remain stationary and are not connected in any way to the movement of the watch. Setting these hands is simply a "visual alarm". Z28 fig.2 shows the wheels below the dial, which are also patented (No. 235072). These wheels are set by the left crown, just like the crown on the right side of the case sets the time.

A later patent (No. 235608) was given to the Z29 fig.1-5, showing its detailed design and function. In Fig.1, we can see that the wheel train consisting of wheels 15, 16, 17 is installed next to the conversion wheel 13 of the wheel train consisting of wheels 11, 12, 14, because there is not enough space under the dial (inside the case). Fig.2 is a cross-section of Fig.1. Fig.3 and Fig.4 show how the setting stem 22 protrudes in the same way as the winding stem normally does. In this unique mechanism, the hands can be set by pulling the crown until it stops moving. This pull of the crown inserts the block 25 into an octagonal hole in the "hand setting wheel" 24.

The section 26, 27 in the setting wheel 22 (Fig. 2) controls the movement of the crown. Once the crown 18 is pushed back, it can rotate either towards or away from the watch, without accidentally resetting the alarm hand. Fig. 5 is a section based on Fig. 2, showing the octagonal hole in the hand setting wheel 23.