Sodium chloride sensing by using a near-field microwave microprobe

The authors observed the NaCl concentration of solutions using a near-field microwave microprobe (NFMM). Instead of the usual technique, they take advantage of the noncontact evaluation capabilities of a NFMM. A NFMM with a high Q dielectric resonator allows observation of small variations of the permittivity due to changes in the NaCl concentration. By measuring the reflection coefficient S-11, they could observe the concentration of NaCl. The measured signal-to-noise was about 53 dB and the minimum detectible signal was about 0.005 dB/(mg/ml). In order to determine the probe selectivity, they measured a mixture solution of NaCl and glucose. (c) 2006 American Institute of Physics.