Novel radio-frequency-based gas sensor with integrated heater

Abstract

Abstract. Up to now, sensor applications have rarely used materials whose dielectric properties are a function of the gas concentration. A sensor principle, by which this material effect can be utilized, is based planar radio-frequency sensors. For the first time, such a sensor was equipped with an integrated heater and successfully operated at temperatures up to 700 ∘C. This makes it possible to apply materials that show gas-dependent changes in the dielectric properties only at higher temperatures. By coating the planar resonance structure with a zeolite, ammonia could be detected. The amount of ammonia stored in the sensitive layer can thereby be determined, since the resonant frequency of the sensor shifts with its ammonia loading. Desorption measurements showed a dependence of the storage behavior of the ammonia in the gas-sensitive layer on the operating temperature of the sensor. Thus, it was possible that by operating the sensor at 300 ∘C, it only shows a gas-concentration-dependent signal. At lower operating temperatures, on the other hand, the sensor could possibly be used for dosimetric determination of very low ammonia concentrations.

B4.4 - Dielectric Properties of Materials used for a Radio-Frequency based NOx Dosimeter

“…The sensor setup, as shown in Fig. 1, is modified compared to a previous design in [1]. The stripline to excite the resonant structure is now shielded on both sides by a ground plane.…”

Characterization and Neural Modeling of a Microwave Gas Sensor for Oxygen Detection Aimed at Healthcare Applications

“…[ 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 ], as well as in therapeutic applications [ 14 , 15 ]. In recent years, various sensors based on microwave devices have been developed to be used for gas sensing purposes [ 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 ]. Compared to their conventional counterparts based on resistive, capacitive, and amperometric effects [ 18 ], sensors based on microwave transducers show better performance, i.e., they have lower power consumption, a shorter response time, and a lower operating temperature [ 16 , 18 , 19 , 20 , 21 , 22 ].…”

“…Therefore, the changes in the target gas concentration influence the changes in the electrical response of the sensor. Often, the propagative structure is realized in the microstrip technology, such as microstrip patch antennas [ 24 , 25 , 26 ], microwave resonators [ 20 , 27 , 28 , 29 , 30 , 31 , 32 ], and other microstrip structures [ 35 , 36 ]. Among the various exploited structures, sensors based on the use of interdigital capacitors (IDCs) as propagative structures have been proposed [ 30 , 37 ].…”

The quality monitoring of paracetamol medicament using a noninvasive microwave sensor

“…In the context of drugs and equivalent substances, many interesting technologies can be found in the literature for qualitative online analysis, such as optical and infrared spectroscopy 11 , chromatographic analysis 12 , and microwave sensing spectroscopy 13 . Microwave sensing technology has long been utilized as a fast and accurate method in research and industrial equipment, such as medical devices for glucose measurement [14][15][16] , gas sensing 17,18 , humidity sensing 19 , or breast tumors 20,21 . This technique may offer an effective way to monitor drug quality in real-time and consequently reduce the time required for this task.…”