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Pulse‐echo methods as used for distance measurements are generally based on the determination of the time of flight between a transmitted pulse and its echo. It is quite easy to measure the exact moment of pulse transmission. However, the moment of arrival is difficult to measure with high accuracy because of interference and noise.

The purpose of this study is to demonstrate the usage of three-dimensionally (3D) printed polylactic acid (PLA)-carbon black (CB) conductive polymer composite in the measurement of the void fraction and liquid level.

PLA-CB conductive polymer composite is 3D printed through fused deposition modelling (FDM) technique and used as a capacitive sensor for void fraction measurement and liquid level sensing. The sensitivity of 3D printed ring and concave type capacitive sensors are compared for void fraction measurement. The effect of electrode length, thickness and pipe dimension on the capacitance achievable for the particular void fraction is studied. Concept of fringing capacitance is used for the sensing of liquid level.

Compared to the concave design comprising four electrodes, the ring-type capacitive sensor produced better results in void fraction measurement. Increase in pipe diameter and electrode length results in the enhancement of capacitance arising from specific void fraction. For a 100 mm diameter pipe, the capacitance of the 150 mm-long concave electrode (0.4 mm thick) increased from 9.98 to 67.77 pF as the void fraction decreased from 100% to 0%. Development of the fringing capacitance in 3D printed PLA-CB composite helps in the measurement of liquid level. Both parallel finger topology and interdigital electrode configuration are able to sense the liquid level.

Ability of the 3D printed conductive PLA-CB composite to act as a capacitive sensor is experimentally analysed. Performance of different electrode configuration is tested for both void fraction measurement and liquid level sensing. Results of experimentation prove that FDM printed PLA-CB composite is suitable for the void fraction and liquid level measurement.

This article describes a new humidity sensor using the technique of differential thermal analysis (DTA). The energy of water vaporisation is estimated via the measurement of the Seebeck voltage of miniature thermocouples used in differential mode on a Peltier module causing condensation from the ambient air. This sensor uses the sensitivity of alloys V2VI3 containing [Bi, Te, Sb, Se], 400‐440μV.K^–1. Experimental measurements have been performed in a climatic chamber at constant temperature. The time variation of the differential Seebeck voltage with relative humidities H_R varying from 10 to 90 per cent makes it possible to identify with precision the point of water evaporation. For each value of the relative humidity, it is directly a function of the condensate mass. The integration of these curves over time makes it possible to calculate the energy of vaporisation and the condensate mass.

This paper presents some aspects of the research activities on sensors for robots, developed in the Instituto de Automatica Industrial (IAI) during the last years. The demand for greater precision in the measurement of distances using US techniques, makes it necessary to compensate for alterations in the sound‐speed in the interposed medium due to temperature. In this paper we will describe a method for calculating this correction in order that no other external sensor be necessary. The method is based on the resonance‐frequency variation of the piezoelectric elements with temperature. The accuracy reached with this correction is higher than normally would be needed in robotics applications.

The purpose of this study is to develop a robot for non-destructive testing of the pipelines to improve its reliability and reduce the loss of products due to cracks, corrosions, etc.

In this study, an inline inspection robot was developed for crack and corrosion detection in the pipeline. The developed robot consists of ultrasonic sensors to avoid obstacles, a visual aid with high resolution to view real time images and colour sensors for corrosion detection. The Autodesk inventor software was used for the drafting and solid modelling of the robot. A dummy pipe of 500 mm diameter and 2,000 mm length with induced cracks and corrosion was fabricated to test the robot. The colour sensors placed at each side of the robot were used to detect corrosion in the dummy pipe whilst the image processing was done to analyse the crack, as well as the type and depth of corrosion present in the dummy pipe.

The results obtained show the ability of the developed robot to detect cracks and determine the crack growth in the pipeline in addition to its ability to determine corrosion.

Hence, the study provides a diagnostic tool for detecting pipeline defects and analysing the extent of defects to determine the fatigue rate and the useful life of the pipeline.

The novelties of this study is based on the fact that it was designed to avoid obstacles and check for cracks, leakage and corrosion in pipelines autonomously. It has visual aid that makes it possible to see the interior of the pipe. This makes it easier to identify the defect and the location of the defects before a catastrophic failure. The device is also equipped with sensors, which can detect defects and send the signal to a control system, as well as a Bluetooth device so the operator can have real time information about the state and integrity of the pipelines. The system is also integrated with a Bluetooth device, which permits its compatibility with Android and other mobile applications. Thus, the enabled user can send a command to query the state of the pipeline at any location with the feedback received in the form of short message service. Hence, this study offers contribution in the development of an independent (self-governing) system with the capability to autonomously detect defects in pipe walls and effectively communicate feedback to the authorised users. The prototype model for the evaluation of pipeline integrity will bring about a more proactive way to detect pipeline defects so that effort can be geared towards its restoration before it becomes a major problem, which will subsequently affect productivity and incur losses.

In this work an original humidity sensor is described. It is based on the study of Seebeck voltage evolution during the water evaporation of a micro‐module Peltier (MMP). The measurement principle is to detect (after cooling) the small temperature decrease created when total water evaporation occurs over the MMP. All the active thin layers of the sensor are made from (Bi₂Te₃)_0.9(Bi₂Se₃)_0.1 (N) films and (Bi₂Te₃)_0.25(Sb₂Te₃)_0.75 (P) films flash evaporated. Experimental measures were performed in a climatic chamber for several values of relative humidity (50 to 90 per cent). The phenomenon (evaporation) appears after a delay time τ. This delay time is the response time of the sensor. Therefore it is possible to draw the evaporation delay time as a function of relative humidity.