ABSTRACT
ABSTRACT: We present a high speed, low cost impedance spectroscope for metal oxide gas sensors. It uses an MLS (Maximum Length Sequence) excitation signal, provided by an FPGA (Field Programmable Gate Array), which is also used for data acquisition. To determine the impedance spectra, we use the ETFE (Empirical Transfer Function Estimate) method, which is used to calculate the impedance by evaluating the Fourier transformations of current and voltage. Thereby, an impedance spectrum with a range from approx. 60 kHz to 100 MHz can be acquired in approx. 16 μs. For the further development of the measurement principle a simulation of the transfer function was carried out using Simulink. Using the spectrometer we built a measurement system for combined TCO (Temperature Cycled Operation)—EIS (Electrical Impedance Spectroscopy) measurements. In such a combined system, impedance spectra should be acquired in a very short time, in which the sensor can be regarded as time-invariant. The system has been tested in exemplary gas measurement applications.
