Liviu Viman

Behavioral model and a MatLAB simulation interface of vibrating wire transducers

This article wants to reveal a new method to measure and moderate a vibrating wire transducer. Combining a complex measuring procedure that includes data acquisition and a MatLab application, it is possible to calculate the transducers impedance. Furthermore, using higher frequencies (as the resonance frequency), respectively lower frequencies signals, the technique above evaluates correctly some parameters that where previously unavailable and also calculates the impedances real and imaginary parts. The above processes are fully automated under MatLAB platform so the transducers impedance to be efficiently calculated.

Wireless data logger for thermal validation systems

This paper describes the software and hardware approach for building a wireless data logger for thermal validation systems. It must meet international and European regulations for validation of pharmaceutical, biotechnology and medical device (EN 285, EN 554, HTM 2010). The temperature range is from −60°C to 150°C with total system measurement accuracy of 0.1°C for all range of measurements. These equipments must measure and function in the specified temperature range.

Electrical model for two coils vibrating wire transducers without mutual couplings

The vibrating wire transducer represents, basically, a damped oscillating resonant circuit tuned on the vibrating wire mechanical resonant frequency. Determining the equivalent electrical circuit for vibrating wire transducers without mutual couplings is a very important step because implementing PSPICE models for the behavior analysis cannot be made correctly with mutually coupled impedances. The electrical models have a major impact in choosing the excitation method to be used and establishing the best criteria that reveal the main transducer parameters as well. This paper is a follow up of our previous work presented in [3], in which we introduced and validated the electrical coupled model for two coils vibrating wire transducers.

Techniques to implement A/D converters using minimal hardware and software

Many products currently take advantage of microcontroller and are capable of creating an analogue - to - digital (A/D) converter with very little extra hardware or software. In effort to make the design more competitive, the typical successive approximation A/D converter (ADC), on board, can be replaced by several low - cost A/D PWM converter structure. The designer must first determine the true system requirements and then select an approach that best meets those requirements. Quite often when a discrete ADC is designed, tradeoffs must be made between parameters such as speed versus resolution and high accuracy versus low cost. Besides the actual input signal parameters (rate of change and range) and converter parameters (accuracy and resolution), other tasks that need to be performed by the microcontroller circuit (real -time monitoring /control) often play a major role in witch method is optimum.

An accurately method for measuring resistive transducers from hydro-energetic constructions

To ensure the hydro-energetic building reliability, specific quantities need to be monitored. The temperature, pressure, deformation, mechanical stress, etc. are often measured using resistive gauges, spread in the whole structure of the construction. The resistive transducers are based on the resistive variation and constructive are realized by one or two resistances in serial connection. To measure the resistive transducer can be used the consecrate method, Wheatstone bridge. To define the Wheatstone bridge is used one or two resistances from transducer, and other two is the reference resistor, located on the measurement system, which complete the circuit. Because the measurement is make different atmospheric condition (summer, winter), reference resistances are changing the value. For this cause using the reference resistor introduce the measurement errors. An embedded microcontroller system with a programmable analog to digital converter, which used only the transducer resistances, eliminates the error dependents by temperature and compensate the connection wires. The purpose of this article is a measurement method using a 16 bit sigma delta converter, which give the 0.001% precision for obtain values

PCB design considerations for wireless Data Logger used for thermal validation system

Printed circuit board layout becomes more complex because of the increased devices pin density and system frequency, respectively. A successful high-speed board must effectively integrate devices and other elements while avoiding signal transmission problems associated with high-speed I/O standards. This paper provides guidelines for effective 2.4GHz wireless Data Logger used to measured temperature, regarding the following issues: PCB material selection, transmission line layouts, routing schemes for minimizing crosstalk and maintaining signal integrity, and electromagnetic interference. The Data Logger temperature range is from −60°C to 150°C with accuracy of 0.1°C for each measurement.

Impedance Meter based on IQ Demodulators

The paper is focused on using quadrature demodulators in a measurement system. Quadrature demodulators are widely used in radiofrequency and communication fields. By using those demodulators, the measurement system is able to detect and quantify phase shift between the voltage and the current that flows through an unknown impedance.

Flat pipe cooling system for SMD chips

This paper describes a specific cooling system based on forced convection. The main purpose of the system is to evacuate the heat generated by power surface mount components like: high speed converters, high frequency clock synthesizers, linear circuits etc. During the study, the main heat transfer types as conductive and forced convection were described using a mathematical model of the system. Due to the fact that forced convection heat transfer is one of the most used cooling solutions in electronic design, the actual paper focuses on the design and implementation of a cooling system based on a flat aluminum pipe as airflow guidance element. A comparison between different materials and filling techniques for thermal via in order to achieve small thermal resistance was made as well.

Implementation of a microwave elliptical low pass filter with radial stubs

Actual paper describes two implementation methods of an elliptical low pass filter using copper disc sectors on a PCB substrate. The main idea was to replace the series resonant branches of the filter circuit with radial stubs, which have the same equivalent circuit at high frequencies. Different approaches of the shapes and placement of the radial stubs were made during the study. Substrate material of the printed circuit board and the dielectric permittivity variation as a function of frequency were also characterized. Radial stubs are largely used for decades in microwave applications and they created a solid background for further studies or scientific research.

XpertTrack: Precision Autonomous Measuring Device Developed for Real Time Shipments Tracker

This paper proposes a software and hardware solution for real time condition monitoring applications. The proposed device, called XpertTrack, exchanges data through the GPRS protocol over a GSM network and monitories temperature and vibrations of critical merchandise during commercial shipments anywhere on the globe. Another feature of this real time tracker is to provide GPS and GSM positioning with a precision of 10 m or less. In order to interpret the condition of the merchandise, the data acquisition, analysis and visualization are done with 0.1 °C accuracy for the temperature sensor, and 10 levels of shock sensitivity for the acceleration sensor. In addition to this, the architecture allows increasing the number and the types of sensors, so that companies can use this flexible solution to monitor a large percentage of their fleet.