From the Dive Computer to the Pressure Gauge

KELLER played a key role in the production of the very first dive computer. The components of the dive computer would later be used to create the very first digital pressure gauge. Learn more about this story, which begins with the first ever dive computer and continues with today's KELLER pressure gauge series.

The origins of the dive computer and the connection with KELLER

The story of electronic decompression dive computers begins with Albert A. Bühlmann, a Swiss professor of medicine. He worked at the University of Zurich, where he set up a pressure chamber laboratory in 1960. He became known for his research in the field of diving medicine, especially decompression theory. He developed decompression tables and models for calculating saturation processes in the human body. These models were later used as the basis for the development of many dive computers.

Decompression

Decompression is the term used to describe the controlled reduction of pressure when diving. Decompression is managed using empirical «decompression tables» or with the help of dive computers. These are based on the decompression model. Dive time, dive depth and other factors determine how much inert gas (primarily nitrogen) accumulates in the body and thus how much decompression time is required.

In 1981, Jürgen Hermann at ETH Zurich managed to successfully implement the decompression model on an Intel microcomputer. This resulted in the first decompression computer that calculated not only the no-decompression limit, but also the decompression levels for complex multi-level dives in real time. The miniaturisation of the hardware resulted in a lightweight, energy-efficient dive computer known as the «Hans Hass Deco Brain». The «Deco Brain» simulated twelve different types of body tissue and went into production in 1983 in partnership with the company Divetronic AG. KELLER’s PA-10/20 bar (today’s 10L series) was used for depth measurement. The dive computer was manufactured at KELLER's site in Winterthur.

Tissue saturation

The body is divided into different tissue types. The saturation time varies for each tissue type, with this being determined by blood flow. Saturation of the tissue is exponential. These saturation times are expressed as «half-times». They indicate the period of time in which a tissue becomes 50% saturated with an inert gas.

Rapidly saturating/fast tissue  
Nerves, brain, spinal cord, blood, kidneys                     
Half-time: 3–15 min.

Medium tissue 
Muscles, skin, stomach, intestine                                 
Half-time: 20–150 min.

Slow tissue      
Bones, cartilage, fatty tissue                            
Half-time: 150–360 min.

Silent bubbles and decompression sickness

Some of the excess nitrogen dissolves into microscopic pockets of gas that form tiny bubbles. These tiny bubbles can grow into larger, but still harmless «silent bubbles». These bubbles then make their way to the lungs. If the silent bubbles join together to form larger ones or if large bubbles form directly, this causes decompression sickness.

The resulting bubbles of gas can cause mechanical injury to the tissues or joints. A gas embolism can form inside blood vessels, causing a localised interruption to the blood supply. In the brain, blockages of the blood supply can trigger a stroke.

In 1985, the first successor model, the «Deco Brain II», was created. It was based on an optimised calculation model. The use of NiCd batteries increased the maximum possible operating time to 80 hours. One year later, the material used to make the Deco Brain housing was changed from aluminium to a cheaper plastic. However, this proved to be a grave error. Contact with soap or shampoo and large fluctuations in temperature caused stress cracks to appear in the housing. During dives in cold environments, such as winter diving in mountain lakes, the water in the housing’s pressure inlet would also freeze. As water expands greatly when it turns to ice, many sensors were placed under excessive mechanical strain, causing the measuring cell to break. This led to shockingly high replacement and repair costs and a great deal of damage to the product’s image. Just one year later, in 1986, production of the «Deco Brain» was discontinued entirely.

The «Senso Brain» innovation and development of the «Micro Brain»

In 1987, Hermann developed the «Senso Brain», a revolutionary innovation. It was the world's first IC sensor signal processor and it served as the link between sensor and microprocessor. Around the same time, Divetronic developed the «Micro Brain» model for Dacor, a former diving equipment manufacturer. The «Micro Brain» was equipped with KELLER’s TAB1 sensors.

Takeover by KELLER and bankruptcy of Divetronic AG

Due to the loss of image suffered and the steep repair costs, Divetronic AG owed KELLER more than 10,000 sensors in 1985. This corresponded to a value of more than one million Swiss francs. KELLER took over the company before having Divetronic AG file for bankruptcy. KELLER sold the remaining tools and systems to Dacor.

Development of the first intelligent pressure gauge

Following Divetronic AG’s bankruptcy, KELLER had around 10,000 displays in stock. There were two options: throw away the displays or use them for another product. For Hannes W. Keller, founder of KELLER Druckmesstechnik, the choice was obvious. KELLER did not have any budget-friendly pressure gauges in its product portfolio at that time. So that Divetronic's displays could be put to further use, plans were made to develop a simple gauge with a peak value memory. This pressure gauge was given the name «Piccolo» and sold exceptionally well.

KELLER therefore started developing the first «intelligent» digital pressure gauge, based on the «Senso Brain». The «Intel-Mano», a name that is still in use at KELLER today, was an innovation that took the market by storm in 1992. The one-button operation was revolutionary at the time, but users had to use the device regularly in order to learn how to navigate the menu structures. KELLER sold more than 8000 of these over the years.

The housing was initially made from milled aluminium, although this was later replaced by plastic housing. KELLER’s LEO1, LEO3, LEO-Record and LEX1 pressure gauges still retain this same basic shape.