50 years in pressure measurement technologies

Leading article in a German magazine, April 2004

It all started in 1964 with my first job at «Kistler AG». It was there that I came to the sobering realization that my schooling and university education had very little help in solving the tasks set before me. Much more useful was the advice to consider school as a place where you learn how to think, but not a place to accumulate knowledge. You just have to completely forget all school knowledge. I absorbed this truth. From that moment on, I focused on solving the problem as a police inspector focuses on solving a crime. Suddenly, the solution became crystal clear, and I asked myself: «How could I have been so blind?»

The same was true with design tasks. Only after long searches was a solution found, full of clarity, and I again and again asked myself: «Did we really learn to think in school if the solution could have been so close, but it was light years away from us?» Why did Copernicus have to take such roundabout ways to come to the conclusion that the Earth rotates? Shouldn't it have been obvious by itself, simply when we look at the clear night sky? After all, it is visible that a huge space rotates around us every day? Looking back 40 years at the history of pressure sensor technology, I ask myself the same question: «Why does it take so much time to produce $10 pressure sensors? Why haven't electrical manometers replaced mechanical ones back then?».

A look back

Earlier in the USA, the importance of sensors for the future was recognized. Engineers with experience in sensors were rare, and in 1966 I got a position at «Honeywell» in the research center in Minneapolis, where there was already a diffusion line for producing flat circuits. The theoretical basis for attempting to place diffusion resistance on pressure membranes had been prepared; now the technology had to be put into practice. Anthony Kurtz left the center long before I arrived and founded the company «Kulite», producing sensors based on flat diaphragms using metal or ceramics.

From «Honeywell», I was assigned the task of developing a more advanced technology. At the very beginning, I asked why we couldn't use silicon as the back surface for sensors? Art Zias, a well-known guru in this field, answered dryly and to the point: «Too expensive». That settled the matter for me. This was followed by a two-year investigation of alternative materials until in desperation, I turned again to silicon, initiating a technological breakthrough by obtaining a combined monolithic measuring cell. It consisted of silicon plates bonded to a silicon membrane (this design was later replaced by a glass Pyrex back panel combined with a silicon diaphragm).

Art Zias gave me a strange thought: «When you work with a sensor, you must imagine yourself in the position of the material, identify with it, become one with it if you want to perform it to the maximum of its capabilities” At first, I was skeptical of such an idea, but after several attempts the results were fruitful. It was amazing – the advice worked. Soon I was the “Wizard” in sensor manufacturing technologies.

In Minneapolis, I lived in a house equipped with a water supply system. There was a large tank in the basement, with an air cushion, a pump, and a pressure relay. Due to the need to measure pressure in house tanks, a request came from the civil construction division to «Honeywell» for ten-dollar sensors, which were intended to be used to regulate the pump after each use of water. The tank was supposed to hold only five liters of water, while the water jet force would always remain constant. The advantages were clear. And the demand for such sensors would be about a million units per year.

Although at that time an isolated sensor cost $500, I was convinced that such requests would be possible and many similar application areas for this product would be found. But I could not push this idea against the employees of «Honeywell» and returned to Switzerland, to «Kistler».

And so, in 1974, I started my own company with very limited resources. This had its advantages. The lack of money bred improvisation and creativity in our work. The limited stock of equipment forced us to develop in the direction of creating a modular design: one universal pressure cell could be installed in various housings. However, despite much lower prices, sales of our sensors were not successful. We had a product, but we had no market. Then the idea arose to offer pressure sensors without housing, allowing companies that had their own pressure transducer market to place them in their own housings.

Famous companies have now joined the fight, and they all wanted to absorb our company. When this failed, they began developing their own technologies. The company «Haenni», which at the time still had 700 people on staff producing pressure gauges, requested Keller to become the exclusive supplier in this field, but we refused. This was a step that accelerated competition and led to a rapid development in this area. Ten new sensors were born at each stage, although the price of a sensor chip at that time was only 2% of the price of an isolated sensor. The capacitive ceramic cell technology gained an advantage because none of the high-tech companies managed to create a practically applicable sensor housing. Thin-film technology was applied everywhere. And then the story awaited completely wild events, such as the creation of the ceramic bubble by «Bosch» or the sheet metal technology by «Valvo».

Residents of companies such as «Hottinger Baldwin», «Bell & Howell», «Schaevitz», «Sedeme» suddenly saw that their hopes could be swept away and tried to adapt their technologies to new requirements. But it was already too late.

Today there are 200 companies developing their own pressure sensor technologies. Many «live» surprisingly long, thanks to the lack of transparency so common in niche markets. Many of them have changed hands several times and always found foolish buyers. Often these buyers purchase more than one sensor at a time in an attempt to gain competence in the field. It all started in the late 70s with «Schlumberger», «Haenni», and «Legris (Bourdon Sedeme)». Now the largest corporations – «GE», «Honeywell», «Texas Instruments» – have been struck by the fever and started producing sensors. This could not end well. If you let a puma, tiger, panther lose their prey, everyone will try to drive it first into their own territory, where they can handle it better.

Sensor technology needs freedom, sovereignty, and independence. To date, there is no worthy product in our field that was conceived and designed within a corporate group. Tony Kertz from «Kulite» and I myself are the last of a dying breed, for whom money is a means to an end, a way to make a real thing, not the other way around. But at some point, we too will have to leave, leaving behind a rather thin broth instead of soup.