EVALUATION OF MODELING ROUTINES FOR ONLINE IMPLEMENTATION OF THE OPEN-ENDED COAXIAL PROBE

Three different models giving the relationship between the complex ref lection coefficient and the complex permittivity have been evaluated f or use with an open-ended coaxial probe in an on-line measurement syst em: Cole's bilinear model (model 1) and the more sophisticated models of Marsland and Evans (model 2) and Marcuvitz (model 3). The frequency range considered is from 500 MHz to 40 GHz. The results are verified by tests on methanol/water mixtures. The results show that for the pur pose of on-line implementation, Cole's simple bilinear model does not give a significantly reduced precision compared to the more sophistica ted model for the open-ended probe and hence can be advantageously use d due to its simplicity and robustness.