The idea ...

As early as 1978, the American physicist J.A. Thornton came up with the idea of measuring the energy Influx using a small copper plate exposed to an energy beam. [20] If the heating and cooling curves are recorded, the energy input can be calculated from them. However, this probe has the disadvantage that the energy beam has to be switched on and off for the measurement. If the probe is coated during the measurement, there is another problem: the heat capacity of the sensor changes and with it the measured value.

Since that time there have been numerous attempts with other probes. All are characterized by the fact that some thermal effect is used, the intensity of which is measured and a connection to the energy Influx is established.

As early as 2008, as part of my dissertation, suggested by Prof. H. Kersten, University of Kiel, we had the idea that there should be another way.

First of all, we wanted to use a substrate heater whose energy balance is determined by its heating, its radiation and by energy Influx from outside. We tinkered with the theory and figured it should work.

A student from a recognized university of applied sciences was persuaded to build and test such a probe as part of his master's thesis.

The good result was: the principle worked. The less good: During the measurement, you had to wait about 20 to 30 minutes until a valid measured value was available. This was unacceptable, as was the complicated and delicate construction.

What now?

... the realization ...

I was of the opinion that we should apply for a funding project to develop our idea into a prototype for an industrially usable probe. I managed to persuade the director of my institute at the time, Prof. Weltmann, who was also committed to it.

The project was applied for and ... approved.

A total of five companies and two institutes were directly involved in the project. A large number of problems had to be solved during the project period of two years, e.g

• the reduction of the measurement time
• the elimination of unwanted drifts in the measured value
• the development of comfortable and powerful electronics to control the probe and obtain the measured value
• The development of an attractive design of the probe
• How large can the measuring range of the probe be?
• What temperatures can the probe be exposed to?
• Do different temperatures of the probe affect the measured value?
• Is it also possible to measure when the probe is coated?
• What happens when there is a voltage flashover from the plasma?

And many other questions.

At the end of the project, the prototype of a powerful measuring instrument was available, which was impressive and had proven its industrial suitability in many applications. The technology of manufacturing the probe had also been refined and tested down to the last detail.

In addition, other inventions were made during development, such as

• a novel control method by combining two-point control and pi control
• The possibility of a directional measurement
• The operation of the probe in "passive mode", with which energy Influxes can be measured up to almost an order of magnitude higher

After the end of the project, interest in the probe partially died out. No investor was found who was willing to take the risk of setting up industrial production of the probe. A few probes were used here and there. Especially in or through the companies and institutes involved in the project.

It was only a few years later, around 2019, that a Greifswald company decided to include the probe in its portfolio. I was asked if, as an employee, I would be responsible for setting up production, acquiring customers, sales and service. I agreed.

But it shouldn't cost much. Everything was on the back burner.