Marek Vondra

Noise in amperometric NO2 sensor

Nitrogen dioxide (NO2) is a highly toxic gas harmful to the environment, which can be threat to human health even at low concentrations. To overcome limitations of standard solid NO2 sensors based on inorganic materials, a new sensor with solid polymer electrolytes (SPE) was developed. Our study deals with investigation of fluctuation phenomena in the electrochemical NO2 sensor, which is based on three-electrode topology and solid polymer electrolyte. Experimental result shows that generation-recombination (G-R) noise seems to be main components of current fluctuations in this sensor. The concentration of detected matter affects noise spectral density of sensor. As the concentration increases, G-R noise rises and is supposed to be connected with chemical processes on active layer of sensor. The shift of G-R component is supposed to be caused by increased flux density between active layer and environment.

Contact quality analysis and noise sources determination of CdZnTe-based high-energy photon detectors

Experimental studies of the transport and noise characteristics of a cadmium-zinc-telluride (CdZnTe) crystal with symmetric gold contacts and a guard ring electrode have been carried out. The current–voltage (IV) characteristics and the noise spectral density were measured at room temperature in the dark. The sample with a disconnected guard ring electrode showed symmetric characteristics for both bias voltage polarities. The shape IV characteristics indicated the presence of carrier injection, leading to IV characteristics nonlinearity. The semiconductor surface has been identified as the main noise and leakage current source. After connecting the guard ring electrode, the leakage currents were suppressed by two orders and the noise spectral density decreased by five orders. In the case of the connected guard ring electrode, the asymmetry of IV characteristics was observed. The contact with worse rectifying properties had a higher contribution of noise to the detector system. Increasing bias voltage causes steeper detector additive noise growth when the guard ring electrode is disconnected.

A FPGA-PC Based Acoustic Emission System with Logarithmic Preamplifier for Fracture Monitoring

Acoustic emission (AE) is one of the most used nondestructive technique since it offers a great potential due to its ability of quantitative evaluation such as source location and source characterization. A common set of recorded acoustic emission signals has an extraordinarily wide dynamic range. Thus, the input gain of the A/D converter plays a key role due in information loss considering limitation of high signal amplitudes and domination of quantization noise at low levels. The usage of a logarithmic preamplifier extends the dynamic range of conventional A/D converters, thus increases the accuracy and signal-to-noise ratio of weak acoustic emission signals.