Jaeger-LeCoultre’s Master Compressor Diving Pro Geographic

Jaeger-LeCoultre’s history in dive watches stretches back to 1959, when it created the world’s first dive watch with an alarm that could be set to signal the end of elapsed dive time, named the Memovox Deep Sea. Then, in 2007, Jaeger-LeCoultre launched a new dive watch that, again, catapulted the manufacture to leading position in mechanical dive watches: the Master Compressor Diving Pro Geographic.

With this watch, your eyes are naturally drawn to the left-hand side of the titanic 46.3 mm case, where the pressure-sensing device for measuring depth is placed. What Jaeger-LeCoultre refers to as the watch’s membrane comprises 24 elements, and represents 1,500 hours of research and development.

The pressure contracting membrane is innately connected to Jaeger-LeCoultre’s history. One of the brand’s most famous innovations is the Atmos clock, that requires no winding and which derives energy purely from tiny variations in environmental temperature or pressure.

Like the Bourdon Tube, Jaeger-LeCoultre’s membrane system relies on varying degrees of deformation caused by water pressure to derive a depth reading. But it differs from the Bourdon Tube device in three very significant ways. First, the entire system remains outside of the watch, meaning that water never enters the watch, as it does in the GST Deep One.

Second, while the Bourdon Tube relies on the elastic property of metal to return to shape consistently, constancy of the membrane’s variable geometry is controlled by a special spring. This offers greater ease in achieving consistency, and also greater ease in repairing or calibrating the system.

Finally, because the membrane system has a finite travel, after which additional pressure has no effect on it, the watch can be brought beyond its 80-meter maximum displayed depth, with no ill effect. The maximum pressure that can be exerted on the head is 9.9 kg, which corresponds to the 80-meter depth limit of the gauge.

While much has been made of the fact that pressing the head of the gauge allows you to demonstrate the principal of this extraordinary function to friends, a critical benefit to this has been somewhat overlooked.

In other watches with depth gauges, the wearer must actually descend to depth or be fitted with an additional apparatus to determine if the depth gauge is functioning. With the simple yet innovative design architecture of Jaeger-LeCoultre’s depth gauge, you can test if your depth gauge is functioning by simply pressing on the head of the system and observing the movement of the depth gauge hand. This adds a huge margin of safety during pre-dive safety checks.

Panerai Luminor 1950 Submersible Depth Gauge

Founded in 1860, Panerai first developed its expertise in patented luminous substance and the creation of military devices, one of which was the depth gauge. So successful were Panerai’s depth gauges that they formed the cornerstone of the trittico: a combination of dive watch, compass and depth gauge that was standard-issue equipment for Italy’s naval commandos during the Second World War.

Panerai’s depth gauges were calibrated in two versions, both using the Bourdon Tube system. The first version read depths to 15 meters and was used primarily for attack missions where divers would swim out to enemy objectives at relatively shallow depths, to either place ordinance on hulls, or guide their torpedoes to deadly destinations. The second version was rated to 30 meters and used for what the Italian Navy termed “defense missions”.

The idea of combining two of the key components of Panerai’s legendary trittico was certainly not lost on its dynamic CEO Angelo Bonati. He explains, “We worked on the Submersible Depth Gauge for a good five years. It took such a long time because we wanted to attain the certification as a professional diving instrument from the Swiss Federal Office for Metrology (METAS) in Bern.”

Bonati had several mechanical depth gauges tested before deciding on an electronic one. The Luminor 1950 Submersible Depth Gauge watch, at 47 mm in diameter, features a titanium case and a uni-directional rotating bezel. The depth gauge registers pressure using a silicon diaphragm that interacts with water pressure through the thin fins in the watch back. But the movement driving the time and date indications is mechanical — a reliable Valjoux-7750-based caliber with its chronograph functions suppressed.

The depth scale is located on the outer perimeter of the dial. At the end of the scale is the “off position” resting place for the depth gauge. When you press the small push-piece at ten o’clock, the gauge is activated, and its hand automatically travels to the deepest dive reading during the previous dive. Press it again for six seconds; it returns to zero, and you can begin your dive.

The watch takes a measurement for depth every 1.25 seconds with a margin of error of about 20 centimeters. At any time during the dive, you can check your maximum dive depth by pressing the push-piece at ten o’clock.

After six seconds, the hand will return to your current depth. The maximum dive time is four hours, and the battery of the depth gauge mechanism is good for 500 hours. When battery life is diminished, the depth gauge hand will move slowly between the off and zero positions.

While the implementation of electronic technology is markedly different from the depth gauges created in its past, Panerai’s history in the creation of the devices gives it great legitimacy to create this type of timepiece.