Virtual instrument for power quality research

Peer Reviewe

Improving the resolution in direct inductive sensor-to-microcontroller interface

Postprint (author's final draft

Microcontroller-based interface circuit for inductive sensors

This work proposes a fully-digital interface circuit for the measurement of inductive sensors using a low-cost microcontroller (µC) and without any intermediate active circuit. Apart from the µC and the sensor, the circuit just requires an external resistor and a reference inductance so that two RL circuits with a high-pass filter (HPF) topology are formed. The µC appropriately excites such RL circuits in order to measure the discharging time of the voltage across each inductance (i.e. sensing and reference) and then it uses such discharging times to estimate the sensor inductance. Experimental tests using a commercial µC show a non-linearity error (NLE) lower than 0.5%FSS (Full-Scale Span) when measuring inductances from 1 mH to 10 mH, and from 10 mH to 100 mH.Peer ReviewedPostprint (published version

Improving the single point calibration technique in direct sensor-to-microcontroller interface by increasing nonlinearity

Peer Reviewe

Differential inductive sensor-to-microcontroller interface circuit

This paper proposes a low-cost interface circuit for differential inductive sensors where the sensor is directly connected to a microcontroller unit (MCU) without any active intermediate electronics in between. The timer embedded into the MCU is employed to measure the discharging or charging time interval of two passive RL networks formed by each sensor coil and an external resistor. Two topologies of the circuit are presented, evaluating their advantages and drawbacks. One of the topologies is implemented using a low-cost 8-bit MCU (Atmel ATmega328P) and its transfer characteristics is evaluated when measuring a commercial displacement inductive sensor. Experimental results show that, in a range of ±25 mm, the non-linearity error is smaller than 1%, and the resolution is 9 bits for an overall measuring time of a few milliseconds.Peer ReviewedPostprint (published version

Differential inductive sensor-to-microcontroller interface circuit

This paper proposes a low-cost interface circuit for differential inductive sensors where the sensor is directly connected to a microcontroller unit (MCU) without any active intermediate electronics in between. The timer embedded into the MCU is employed to measure the discharging or charging time interval of two passive RL networks formed by each sensor coil and an external resistor. Two topologies of the circuit are presented, evaluating their advantages and drawbacks. One of the topologies is implemented using a low-cost 8-bit MCU (Atmel ATmega328P) and its transfer characteristics is evaluated when measuring a commercial displacement inductive sensor. Experimental results show that, in a range of ±25 mm, the non-linearity error is smaller than 1%, and the resolution is 9 bits for an overall measuring time of a few milliseconds.Peer Reviewe

Generation of Long-time Complex Signals for Testing the Instruments for Detection of Voltage Quality Disturbances

Software supported procedure for generation of long-time complex test sentences, suitable for testing the instruments for detection of standard voltage quality (VQ) disturbances is presented in this paper. This solution for test signal generation includes significant improvements of computer-based signal generator presented and described in the previously published paper [1]. The generator is based on virtual instrumentation software for defining the basic signal parameters, data acquisition card NI 6343, and power amplifier for amplification of output voltage level to the nominal RMS voltage value of 230 V. Definition of basic signal parameters in LabVIEW application software is supported using Script files, which allows simple repetition of specific test signals and combination of more different test sequences in the complex composite test waveform. The basic advantage of this generator compared to the similar solutions for signal generation is the possibility for long-time test sequence generation according to predefined complex test scenarios, including various combinations of VQ disturbances defined in accordance with the European standard EN50160. Experimental verification of the presented signal generator capability is performed by testing the commercial power quality analyzer Fluke 435 Series II. In this paper are shown some characteristic complex test signals with various disturbances and logged data obtained from the tested power quality analyzer