This paper addresses the problem of fertiliser characterisation using optical and electrical impedance methods. Comparative analysis was performed to estimate the methods effectiveness for quantitative and qualitative characterisation of water diluted fertiliser. Characterisation using optical method within the ultraviolet range indicates the variability of features that was not observed when using the impedance method. The combination of both methods showed potential for more accurate qualitative analysis than each method alone. Both methods showed good sensitivity to fertiliser concentration variation.
COBISS.SI-ID: 12227668
In this paper an operational transconductance amplifier [1] with temperature compensation is presented. It is a voltage-controlled current source, which operates in an open loop configuration with a single output connected to a resistive load. The amplifier is internally compensated to keep the gain stable over the -40 °C to 125 °C temperature range. It features low input voltage noise and operates at supply voltages from 3 V to 5.5 V. Additionally, an internal 1.21 V bandgap reference is used to ensure a stable internal voltage reference point. The active area of the proposed integrated circuit designed with 0.18 µm Bipolar, CMOS, DMOS (BCD) technology is 750 µm x 260 µm. It consumes 423 µA of current and it has 8.87 nV/SHz of input noise at 500 kHz. The resulting simulated voltage gain is 40 dB and variations are less than ±0.3 dB over the temperature range of -40 °C to 125 °C.
COBISS.SI-ID: 11945300
The paper presents a methodology to design, model and efficiently simulate the MEMS electromechanical ?? modulator of the electromechanical analog-to-digital converter with high resolution and high accuracy. The methodology is based on a systematic transformation of a continuous time model of the mechanical part and a continuous time model of an additional electronic loop filter into a unified discrete-time model using an impulse invariant transformation. It can be used to design a MEMS sensor system working in a closed loop where the transfer function of the mechanical part does not provide enough attenuation of the quantization noise,making it impossible to build a high resolution electromechanical ?? modulator with no additional attenuation of the quantization noise. It enables a systematic treatment and fast and efficient simulation, thus providing the possibility to verify and optimize the characteristics of different architectures of the MEMS electromechanical sensor systems in a very short time.
COBISS.SI-ID: 11375956
This paper presents the design, modelling and optimization of a 3rd order, hybrid, ?? modulator with an optimized FIR-DAC filter in the feedback to reduce the effect of the clock jitter on SnR of the modulator. The FIR-DAC filter performs a digital-to-analog conversion (DAC) of the one-bit bit-stream, behaving as a multi-bit DAC, while keeping the one-bit linearity performances. The output signal of the modulator (one-bit bit-stream) is converted into a multi-bit output current, which reduces the effects of the clock jitter. The modulator’s performance is optimized by using high-level modelling of the circuits and jitter effects. The presented design, modeling methodology and optimized circuit of the FIR-DAC filter make it possible to reduce the jitter effect; SnR can be 110dB at a normalized jitter smaller than ?ji/Ts?10-5.
COBISS.SI-ID: 11607892
Design, implementation and high-level modeling and simulation of a multi-channel sensor system for the vapor trace detection of different molecules in the air are presented in the paper. The detection is based on the change of the capacitance when a target molecules adsorb to the surface of a chemically-modified COMB capacitive sensor. An integrated low-noise analog electronic circuit with corresponding digital signal processing algorithms measures a small capacitance change. The detection limit is in the range below 1aF/?Hz which makes it sure that the detection limit is in the range of three molecules of TNT in 10^12 molecules of the carrier gas in one second, which ranks the sensitivity among the best in the world. The array of differently modified sensors provides the possibility to improve the selectivity; the low-noise signal processing provides a low detection level while a digital signal processing assures a multichannel processing of the signals in real time. A comparison is made between the simulation and measurement results.
COBISS.SI-ID: 11375700