Function Principle

The same type of standard electrochemical sensor normally used in analyzers for diving is used to determine the oxygen content. The helium content is determined on the basis of measuring the speed of sound in the analyzed mixture.

The speed of sound depends on the content of helium and oxygen, and on the temperature of the mixture. The dependence of the speed of sound on pressure is marginal and can be ignored under normal atmospheric pressure. At 0°C the speed of sound is approximately 970 m/s in pure helium, 330 m/s in air, and 315 m/s in pure oxygen. Raising the temperature by one degree raises the speed of sound by approximately 0.175%. The speed of sound in the mixture is described as a non-linear equation of temperature, oxygen content and helium content.

The speed of sound is measured directly as the time it takes for an acoustic impulse to travel between two microphones. This measurement is taken alternately in both directions so that it will be possible to eliminate the influence of the gas flow-rate.

Every analyzer produced is tesed in the complete range of acceptable oxygen and helium values. In addition to the testing of air, pure oxygen and pure helium undergo testing with 12 different calibration mixtures.

Calibration mixtures are gravimetrically mixed from pure basic gases and are exact to withing two decimal places. In addition to exactness, the accuracy of compensation for the influence of the flow-rate of the analyzed gas is also tested.

We deliver the analyser in the new version with Oled Display, together with a simple flow limiter.

Optional is the Set with professional flow limiter, connection hose, power adapter and spare set of O-rings. And of course - watertight case.