Measuring principle of the CGS

Fundamentals

The measuring tube of the CGS sensor is equipped with a temperature and a pressure sensor in order to capture all relevant operating conditions. Once the measuring tube of the CGS is submerged into the fluid, the gas concentration is determined by means of a completely new method which is based on measuring the complex fluid impedance inside the CGS-sensor. Inside the measuring tube, there are furthermore two isolated electrodes: one electrode functions as the sender while the other one functions as the data receiver. The measuring tube is then connected to a corresponding electronic unit. The CGS can be operated either in the stand-alone mode or via personal computer.

The measuring principle of the CGS system is based on the fact that the fluid always consists oftwo components, the unaerated fluid YF and the pure gas YG:

Y = YF + YG    

In practice, an aerated fluid will always be composed of both parts of admittance and can be described as a system between the following two system conditions:

  • no gas phase, which means that there is only unaerated fluid inside the measuring tube
  • no fluid phase, which means that there is only gas/air inside the measuring tube

Between those two extremes, the CGS system shows a linear alignment meaning that the accuracy of the measuring instrument stays constant throughout the entire measuring range.

The calibration procedure

As far as the calibration of the system is concerned, the admittance YG of the gas (100% air-/gas content) is already installed as the first extreme value by flucon. The second extreme value for the unaerated fluid (0 % air-/gas content) must be calibrated once only by the user. After that, the CGS system is ready for the continuous measuring of the gas concentration / the degree of foaming. The calibration procedure is very simple and needs to be carried out once only for each fluid since the corresponding data can be saved in the memory of the CGS and can be restored any time. It does not matter whether the CGS is operated in the stand-alone mode or whether it is controlled via computer using the comfortable and complementary software program.

Advantages of the CGS technology

The CGS system always displays the actual data of the gas concentration at operating pressure (CGp) and also calculates and displays the value for atmospheric pressure (CG0). The measurements are carried out without any unwanted effects on the measuring fluid and are completely independent of the direction of flow as well as of the viscosity of the fluid. These factors only influence the resulting operating pressure and therefore affect the actual gas content indirectly. The measuring tube itself is not dependent on the working temperature; the temperature dependency of the CGS system is only affected by the fluid and is determined during the calibration procedure.