Measuring Devices for Determining Sound Velocity in Liquids

When we noticed that the majority of density meters were used for measuring concentration, we researched for alternatives. In the process, we came across sound velocity, which was expected to show great changes depending on concentration. We could choose between two methods: Creating a standing sound wave between two reflectors and measuring the runtime of an acoustic pulse over a defined distance. We opted for the latter method with a variant we patented ourselves, whereby an electronic oscillator is synchronised over the runtime. The measurand is a frequency again, which can easily be digitally processed, similar to the way it is done in density measurement. Whereas density has been known and used as a fundamental measurand for hundreds of years, knowledge of sound velocity has not been a priori meaningful. We have explored different measurement problems from the perspective of measuring sound velocity in hundreds of laboratory measurements. It was rather by coincidence that we came across the problem of determining the original extract in completely fermented beer, which could be solved elegantly by measuring sound velocity. Then, the SPR (Schallprozessrechner), one of the devices we developed, started its triumph in all breweries of the world.
Professor Kenner (Department of Physiology of the Medical University of Graz) and Professor Leopold were working on the continuous measurement of blood density for determining the blood volume. (At first, only with rabbits). So when the problem of determining the hematocrit level in the blood of astronauts emerged, we were included in the research into this problem. At that time, the launch of our “Austronaut”, Dr. Franz Viehböck, was just being planned. But soon it turned out that density measurement was unfeasible in zero gravity. We achieved better results using a measuring cell on the basis of sound velocity and built a device in our workshop that finally facilitated the desired measurements in outer space. This was a next step after entering medical technology. We developed a device for determining the blood volume during the dialysis of patients with renal insufficiency. We soon realised that this project was out of our range. Fortunately, a competent company helped us out, which bought the licence for the device, took care of the clinical tests, and ultimately arranged the worldwide distribution of our method.