Distance and Cable Length Measurement System

A simple, economic and successful design for distance and cable length detection is presented. The measurement system is based on the continuous repetition of a pulse that endlessly travels along the distance to be detected. There is a pulse repeater at both ends of the distance or cable to be measured. The endless repetition of the pulse generates a frequency that varies almost inversely with the distance to be measured. The resolution and distance or cable length range could be adjusted by varying the repetition time delay introduced at both ends and the measurement time. With this design a distance can be measured with centimeter resolution using electronic system with microsecond resolution, simplifying classical time of flight designs which require electronics with picosecond resolution. This design was also applied to position measurement

Current Step Generation and Measurement with Rise-time in the Range of Nanoseconds

A current step generator based on a charged coaxial cable is designed and tested for characterizing impulse current shunts. This thesis has developed a traceable calibration infrastructure for fast shunts and other current sensors, defined measurement techniques for a current step and improved the test procedure and measurement capabilities. For calibration of shunts, current coil sensors are used in the measurement circuits. Since no calibration services are currently available for impulse current measuring systems, a best circuit combination is proposed for current step generation with a rise time of less than 5 ns, along with a proposed reference shunt that aims to provide the best and most stable measurement results with negligible noise, oscillations, and droop in the measured current step. Based on techniques found in the literature, current steps are generated, and different sensors were used to measure the generated steep front current steps. The generation system consists of a 110-m long, 50-Ω coaxial cable and a spark gap. Various spark gap switches, including the SF6 spark gap, are used for generating current steps. With the coaxial cable charged from one end, a current step is generated after reflecting back from the open end with a step length of twice the cable transmission delay. The cable is than discharged to the shunt (or coil) through the spark gap. The measurement system consists of shunts and coil current sensors, 5:1 and 6.6:1 attenuators based on the requirement of the sensors. The recording instrument is a 1-GHz, 8-bit, 1-GS/s digitizer. The proposed step generator can produce current steps with a stable current of up to 100 A. The rise time of the step varies from 1.6 ns to 15 ns, depending on the spark gap used for switching. The produced current is constant within 0.5% for a step length of 960 ns generated with a coaxial cable 110 m in length. To improve the test procedure and measurement capabilities, the thesis also analyzed factors affecting current step measurement, such as the type of coaxial cable, type of connection, extra shielding, clearances, interference sources, media of the spark gap, and the spark gap electrode distance (arc length). It is found that the measurement system and the rise time of current step is affected by many factors, including the coaxiality of the connection, impedance mismatch, interference, clearances, stray capacitances, and stray inductances. These results will enable future standardization of impulse current sensors

Design and Development of a Fiber Break Monitoring System in Optical Fiber Communications

Fiber optic cable has been used widely in network communications system.It has being a favorable choice since it offers many advantages,such as immunity to electrical interference, lightening, high bandwidth and security. Due to the massive deployment of optical fiber cable, networks based on this medium needs significantly good monitoring and protection scheme to ensure its availability, especially for critical networks.Current approach uses a system known as Remote Fiber Testing System (RFTS) or Remote Fiber Monitoring System (RFMS).RFMS allows an operator to remotely monitor the condition of a fiber cable by using Optical Time Domain Reflectometer (OTDR). The requirements to place OTDR permanently for continuous monitoring force the line owners to place a high investment to the system.Moreover, placing OTDR is overkill since most of the faults in the fiber optic cable are due to the fiber break.This thesis presents a new approach of monitoring and detecting fiber break by using a simpler device, significantly less expensive yet gives an appropriate measurement to the distance break in place of the OTDR–based RFMS. The design and development of the system, namely Fiber Break Monitoring System (FBMS) will continuously monitor the optical signals in the live fiber cable. The device automatically measures the distance when it detects the break. The distance is measured by analyzing the propagation time of the Fresnel reflection, occurred at the end of the surface break to be detected by the detector module inside FBMS. The study is carried out in both simulation and experiment. The typical performances for analyzing the performance of FBMS are the length resolution, event deadzone, sampling resolution, accuracy, dynamic range and pulsewidth. Those performances were compared to the typical OTDR. This study has proved that FBMS is practicable for a real time monitoring, detecting a fiber break and giving an acceptable result to the distance measure

Lorentz contraction, Bell's spaceships, and rigid body motion in special relativity

The meaning of Lorentz contraction in special relativity and its connection with Bell's spaceships parable is discussed. The motion of Bell's spaceships is then compared with the accelerated motion of a rigid body. We have tried to write this in a simple form that could be used to correct students' misconceptions due to conflicting earlier treatments.Comment: Modified the discussion in Sec. 2. This version to be published in European Journal of Physic

On the Exploitation of Admittance Measurements for Wired Network Topology Derivation

The knowledge of the topology of a wired network is often of fundamental importance. For instance, in the context of Power Line Communications (PLC) networks it is helpful to implement data routing strategies, while in power distribution networks and Smart Micro Grids (SMG) it is required for grid monitoring and for power flow management. In this paper, we use the transmission line theory to shed new light and to show how the topological properties of a wired network can be found exploiting admittance measurements at the nodes. An analytic proof is reported to show that the derivation of the topology can be done in complex networks under certain assumptions. We also analyze the effect of the network background noise on admittance measurements. In this respect, we propose a topology derivation algorithm that works in the presence of noise. We finally analyze the performance of the algorithm using values that are typical of power line distribution networks.Comment: A version of this manuscript has been submitted to the IEEE Transactions on Instrumentation and Measurement for possible publication. The paper consists of 8 pages, 11 figures, 1 tabl

Evaluation of a Local Fault Detection Algorithm for HVDC Systems

A great increase in the amount of energy generated from clean and renewable sources integrated in the electric power system is expected worldwide in the coming years. High Voltage Direct Current (HVDC) systems are seen as a promising alternative to the traditional Alternating Current (AC) systems for the expansion of the electric power system. However, to achieve this vision, there are some remaining challenges regarding HVDC systems which need to be solved. One of the main challenges is related to fault detection and location in HVDC grids. This paper reviews the main protection algorithms available and presents the evaluation of a local fault detection algorithm for DC faults in a multi-terminal Voltage Source Conversion (VSC) based HVDC grid. The paper analyses the influence of the DC voltage sampling frequency and the cable length in the performance of the algorithm. © 2019, European Association for the Development of Renewable Energy, Environment and Power Quality (EA4EPQ).The authors thank the support from the Spanish Ministry of Economy, Industry and Competitiveness (project ENE2016-79145-R AEI/FEDER, UE) and GISEL research group IT1083-16), as well as from the University of the Basque Country UPV/EHU (research group funding PPG17/23)

Wireless distance estimation with low-power standard components in wireless sensor nodes

In the context of increasing use of moving wireless sensor nodes the interest in localizing these nodes in their application environment is strongly rising. For many applications, it is necessary to know the exact position of the nodes in two- or three-dimensional space. Commonly used nodes use state-of-the-art transceivers like the CC430 from Texas Instruments with integrated signal strength measurement for this purpose. This has the disadvantage, that the signal strength measurement is strongly dependent on the orientation of the node through the antennas inhomogeneous radiation pattern as well as it has a small accuracy on long ranges. Also, the nodes overall attenuation and output power has to be calibrated and interference and multipath effects appear in closed environments. Another possibility to trilaterate the position of a sensor node is the time of flight measurement. This has the advantage, that the position can also be estimated on long ranges, where signal strength methods give only poor accuracy. In this paper we present an investigation of the suitability of the state-of-the-art transceiver CC430 for a system based on time of flight methods and give an overview of the optimal settings under various circumstances for the in-field application. For this investigation, the systematic and statistical errors in the time of flight measurements with the CC430 have been investigated under a multitude of parameters. Our basic system does not use any additional components but only the given standard hardware, which can be found on the Texas Instruments evaluation board for a CC430. Thus, it can be implemented on already existent sensor node networks by a simple software upgrade.Comment: 8 pages, Proceedings of the 14th Mechatronics Forum International Conference, Mechatronics 201