Petr Neumann

Improved design of the uninterruptable power supply unit for powering of network devices

Paper describes suggestions on the improvement of the common On-line structure of the uninterruptible power supply units used for powering of network devices. According to these suggestions a prototype circuit able to deliver the output power up to 150 W was constructed. The topology was optimized in order maximum efficiency was achieved when the output is fed by an accumulator in order the operating time was as long as possible.

Influence of the Antenna’s Height to the Standing Waves Ratio When Performing the Electromagnetic Susceptibility Tests in Anechoic Chambers

Immunity tests to radiated electromagnetic field are one of the most common tests performed within the framework of the electromagnetic compatibility. These tests are performed inside a shielded chamber provided the requirements given by the appropriate standards are kept. As the levels of the generated fields can be high and the output power of the transmitting amplifiers cannot be infinite, it is necessary to achieve a good performance of the transmitting antenna. By means of the real experiment the author of this paper shows how the height of the antenna placed above the conductive floor can affect the antenna’s voltage standing waves ratio and how this phenomenon affects the parameters of the whole measurement system.

The Microcomputer Application in Physical Principles Demonstration Model Design

The article describes a design of a microcomputer system which is realized in the educational scale model control for physical principles demonstration. That particular design project was a part of the educational facility complex project called Experimentarium aiming at basic school and high school students. The article introduces two racing car models controlled by a microcomputer. The first model set demonstrates the speed and acceleration calculation based on a real time measurement. That calculation result can be compared with results obtained during a running man experiment. The second car model set demonstrates a downforce keeping the car riding the ceiling with wheels upside down. The microcomputer control system is based on microprocessors by Atmel, and the system is described in details including illustrative pictures, schematics and graphs.

The Gas Tiny Flow Measurement Instrumentation.

The paper presents the design and experimental experience with the gas flow measurement instrument for the range of (5 – 25) ml/hr. The aimed application area is in a biochemical laboratory for the study of reaction kinetic of sediments decomposition in waste water. The time – of – flight type of sensor with one upstream and one downstream temperature sensor has been chosen for the study. We explain the basic operation principles of the tiny flow measurement and the sensor structure. In the numerical model paragraph, we are describing the basic configuration model and the modelling results. As the three – dimensional simulation would be very time consuming process, we have simplified the simulation for only two – dimensional task. The presented diagrams are derived for different gases (air, nitrogen, carbon oxide and chlorine) and sensor tube materials, namely steel, copper, and plexi-glass. We present also the experimental set – up including the design and sensor parameters. The paragraph with experimental results and discussion on them illustrates the good correspondence with expected values. The paper concludes with the employment of designed gas flowmeter in the biochemical laboratory. INTRODUCTION The accurate measurement and control of tiny liquid flows in the amount of nanoliters up to milliliters per minute is becoming more and more important for a lot of applications in the life science. In some applications, such as process control in precise semiconductor manufacturing, chemical and pharmaceutical industries and biochemical engineering, miniaturized liquid flow sensors are more and more encountered. Most of them operate on the method of thermal transport and are fabricated from a silicon crystal by using micromachining technology. The thermal devices for flow measurement may be grouped in two different classes. The first class groups thermal mass flowmeters that are measuring the effect of the flowing fluid on a hot body (the increase of heating power with constant heater temperature, the decrease of heater temperature with constant heating power). They are usually called hot – wire, hot – film sensors or hot – element sensors. The resistive element is used both as heater and as sensor simultaneously. The temperature can be obtained from its electrical resistance. The second class group thermal mass flowmeters that measure the displacement of temperature profile around the heater which is modulated by the fluid flow. These sensors are called calorimetric sensors. The special type of thermal mass flowmeters in the class mentioned above is thermal mass flowmeter that measure the heat pulse passage time over a known distance. They are usually called time – of – flight sensors [1]. Many of the microflow sensors use a thermopile as a temperature sensor; however, the thermoelectric coefficient of the standard elements used in the integrated circuit is smaller than that of conventional thermocouples. Thus, a resulting output signal may be very small which requires amplifiers integrated directly into the sensor [2]. Up to now, very few of nowadays commercially offered flow sensors are equipped with the features mentioned above. One of possible method of liquid flow measuring is presented in this paper. The properties of a time – of – flight sensor are studied. The FEMLAB program was used for the study of flow sensor properties. SENSOR STRUCTURE AND BASIC OPERATING PRINCIPLE The flow sensor consists of a heater and one or more downstream temperature sensors, as shown in the Figure 1a. The heater is activated by current pulses. The transport of the generated heat is a combination of diffusion and forced convection. The resulting temperature field can be detected by temperature sensors located downstream. The detected temperature output signal of the temperature sensor is a function of time and flow velocity. The sensor output is the time difference between the starting point of the generated heat pulse and the point in time at which a maximum temperature at the downstream sensor is reached, Figure 1b. This type of sensor has the same constraints as the intrusive type of calorimetric sensors: corrosion, Proceedings 29th European Conference on Modelling and Simulation ©ECMS Valeri M. Mladenov, Petia Georgieva, Grisha Spasov, Galidiya Petrova (Editors) ISBN: 978-0-9932440-0-1 / ISBN: 978-0-9932440-1-8 (CD) erosion and leakage [3]. Since the signal processing needs some time to measure the time difference, this sensor type is not suitable for dynamic measurement. On the other side, the advantage of this type of flow sensor is the independence on the fluid temperature in the wider flow range. The influence of fluid properties on the mass flow sensor output is described in [4]. Flow T Q Temperature sensor Heater Temperature

A Model Of Small Airship's Propelling

For the purposes of development of a small and autonomously operated airship, a need to create a model of its propelling and motion has arisen. Being described within this paper, the model defines the requirements that are imposed to motors, propellers and the airships controlling system. The model is based on a typical design of a small airship, that consists of two main propellers, being placed symetrically according to the gondola beneath the airships bladder, and one tail propeller that is placed transversely at the airships tail. According to this model, forces needed to move the airship in the desired direction can be estimated as well as the power consumption of the motors and angular velocity of the propellers. Although the dynamic model of the airship would exceed the framework of this paper, it is also described in broad terms and the results of two main simulations are presented hereby. The simulations describe the behavior of the airship in case of forward acceleration and braking as well as in case of yawing with such braking that ensures reaching of the desired yawing angle.

Industrial process in laboratory environment

This contribution is focused on technical design, development and operation of real time laboratory model which demonstrates principles of industrial automation. The model uses specific multilevel interconnection (Internet/Ethernet - ASI bus) as an example of a higher level of communication between automation systems. The model consists of three interconnected reservoirs where the fluid levels are controlled. Height of the fluid column is measured by modern capacitive sensors and regulated at a constant level by actuators (pump and valves). Inputs and outputs of the system are connected to the central unit, PLC Simatic S7-200 from SIEMENS. Software tools correspond to the type of PLC, specifically a development environment STEP7 - Micro/Win is used. Data transfer from the central unit to the PC server of LABI system is via the LAN/Ethernet and OPC server software.

MODELLING AND DESIGN OF MICROFLOW SENSORS BASED ON MEASURING OF TEMPERATURE FIELD

Abstract This article describes modelling and measurement of tiny liquid flows of the order of microlitres through mililitres per minute. The measurement of mentioned flow range is becoming more and more important for a lot of applications in the life science, analysis, biotechnologies, synthesis (of e.g. pharmaceuticals) and nanotechnology markets. Accompanying demands to flow sensors suited for this low flow range are an extremely small internal volume, the use of for instance PEEK and fused silica as wetted material for the flow sensor tube (instead of stainless steel), and a modular set-up of the instruments, so they can be easily exchanged and adapted to a new need.

B18: Multichannel analog-to-digital converter module with variable gain

Abstract For measurement of some analog signal as voltage, current, resistance etc. and for a different input signal level on multichannel single-ended analog-to-digital converter is necessary to have a variable gain for all input channels. The proposed solution is based on an instrumental operational amplifier on an input stage, where gain level reaches value of 384. An operational amplifier with gain level between 1 and 30 and with offset voltage control is used in the middle stage. Module is ended by 16-bit analog-to-digital converter with a parallel interface compatible with digital signal processors, microcontrollers etc.

Small Gas Flow Measurement - Microcomputer Application in Education

Abstract This paper is focused on education in the field of small gas flow measurement. Students obtain theoretical knowledge in flow and they acquaint with different types of flowmeters. The Department of Automatic Control of Tomas Bata University is equipped with the thermal mass flowmeter (time - of - flight sensor). The theoretical education is on a basis of the mathematical model of energy and temperature balance simulated in the FEMLAB. Students use various constructional materials for design of the thermal mass flowmeter and they verify the properties of designed flowmeter on laboratory models.