Ioan Ciascai

Low–cost capacitive sensor for wells level measurement

The proposed system wants to efficiently substitute the existing level sensors mounted in the dam wells based by its low cost and better precision. The system is been designed around a special designed capacitive sensor composed of eight independent copper pour areas distributed in mirror on from each other. The unknown variables of the resulted mathematical equations are the capacitances and the height of the liquid column (the level of the liquid). The capacitances are been calculated by implementing a measurement system around and AVR microcontroller and a very fast LT1011 comparator.

Statistical analysis of experimental data obtained from the optical pendulum

The experimental measurement devices, in this case optical pendulum is tested to determine the system parameters and also to evidence the system performance. Experimental data obtained from measurement system is affected by errors. It is important to take steps to minimize the errors and also to understand them in order to be better understand the result of the experiment. The statistic analyze of experimental data is used to identify the errors and to reject them. The errors are caused by human inaccuracies like a wrong experimental setup or by the measurement systems errors. A used method is Chauvenets criterion. This can identify the bad data or wild point and discard them from experimental series. Applying a normal statistical test certifies the normal distribution of data and also estimates the confidence level of variance of the experimental data. The transfer function of optical pendulum is a polynomial parametric equation with parameters obtained from experimental data. Erroneous parameters affect the performance of the measurement device. Experimental data processing was done in MATLAB. The measurement system accuracy is by ±55μιη on OX and ±150μιη on OY direction.

Building management system based on image sensor

Physical parameters measures in activity of building management have slow variations. Some of parameters measures are temperature, pressure, movement of some building element. Taking in consideration this hypothesis the measurement system rate acquisition is low. The central unit can be a low speed programmable integrated circuit (IC) like a microcontroller. The low cost and low power consumption of image sensors and the possibility to be ease handled in measurements circuits, recommends the image sensors to be used in building managements. The linear image sensor is high speed device and is used for position detecting. To explore such application in this paper is designed and prototyped an experimental system measurement. The central unit of experimental measurement device is used a FPGA. Image sensor output is an analog voltage; this is easy interconnected with a high speed ADC. The operation frequency of acquisition frequency is established by light integration time. The expose time is computed in concordance with light intensity. The usual operation frequency of FPGA is 50MHz, implementing a soft clock divider the work frequency can be adjusted in same way to not saturate de sensor. The soft application for data acquisition and data analyze are developed in LabView FPGA and, LabView.

A Correlation Method for Improving Temperature Sensors Measurements

The monitoring of hydro-energetic dams implies the permanently checking of the physical parameters that affect its safety. The precision of monitoring depends on the measurement accuracy of the electronic systems. The improper functioning conditions of the measuring system prompt for some sensors the appearance of nonsystematic error. The detection and analysis of these errors has been done. In this paper a method for verifying the correction of temperature measurement is shown. The adjustment of dates is obtained using a correlation method which likens the evolution of temperature from inside of building to a polynomial function. To verify this correction method, the data obtained after processing can be correlated with ambient temperature and with temperature measured by the neighboring sensors. After processing the above mentioned data a correlation value is obtained plusmn1. This value indicates that the sensors function has a very close following of the ambient temperature function and the neighboring sensors function. To improve the results obtained using the correlation method an additional filter is applied to the data source.

Multi - Capacitor sensor algorithm for water level measurement

The water level calculation technique is based on the capacitance measurement of a multi - capacitor sensor partially immersed into the liquid. Every capacitance can be expressed from the mathematical point of view in terms of liquid column height by the geometrical parameters of every capacitor formed. The formula takes into consideration all parasitical effects due to geometrical limitations. The level is calculated using two different algorithms and the compared with a industrial level sensor and a ruler. Finally, the capacitance - level formula is plotted for fastening the level “reading” procedure.

Parasitic influences in a capacitive transducer behavior

The most common parasitic effects involved in a capacitive measurement process are the fringing phenomenon, the error due to unparallel armatures, the capillarity phenomenon, the temperature and humidity influence and the electrical parasitic capacitances induced by the PCB connection traces. The main purpose of this article is to evaluate and extract the total value of those undesired effects from the capacitance measured value, to obtain the correct capacitance value. By combining a mathematical approach with the measurement procedures, the parasitic capacitances were deducted.

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

Electrical model of a capacitive based level sensor

The capacitance level measurement process involves first of all knowing the capacitance of the sensorial part of the built system. For the parallel plate capacitive sensor behavior modeling, it is mandatory to take into consideration the influence of the dielectric materials between the plates. Also, knowing the dielectric position in respect with the capacitors plates, respectively the total parasitic capacitance, the electrical model of the multi-capacitive sensor can be revealed.

Real-time sensor acquisition interfacing using MatLAB

One of the most important procedures which must be done in the dams monitoring process, from the dam behavior point of view, is the analysis of the data acquired from the sensors mounted inside or in the proximity of the dam. The analysis can be done in two ways: real-time - using a direct dedicated interfacing algorithm with one or more sensors, respectively a so called historical analysis - using large data packets acquired during long time periods. The first acquisition procedure shows the behavior of a sensor at an exact moment, while the second reveals - in the end - the dam behavior and suggests the proper actions that must be taken to secure the dam infrastructure.

Sensor measurement errors detection methods

This paper studies the methods of gross errors identification of transducer measurements from hydro energetic building especially from dams. The transducer used in dams monitoring is read every day during the year. The obtained information with one transducer can be seen as the discreet answers of a system. The erroneous measurements appear as a large variation from normal characteristics. The correction methods are mainly based on digital signal processing and approximation function. This paper proposes three method of correction: digital low pass filter, adaptive filter and approximation function. For low pas filtering is used a FIR (Finite Impulse Response) filter with Hamming window. An FIR filter is always stable, realizable, and provides a linear phase response under specific condition. These characteristics recommend FIR filter many filter design. Ambient temperature is the cause of the physical parameter variation detected with transducer. For error correction is applied an adaptive filtering, using the desired response. The approximation method function is less exhaustive and is based on the velocity of variation of result data from day to day. The data which is not respecting these conditions is removed. These three methods are used to determine a maxim correlation between results signals and original signal.