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Position P (top) and uncertainty σP (bottom) vs time. Input signal from the waveform generator has f=1kHz and Vpp=8V.
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Linear variable differential transformer (LVDT) position sensors are widely used in particle accelerators and nuclear plants, thanks to their properties of contact-less sensing, radiation tolerance, infinite resolution, good linearity and cost efficiency. Many applications require high reading accuracy, even in environments with high radiation leve...
Citations
... Linear variable differential transformer (LVDT) sensors are the type of devices that are widely used in industry to measure displacement or linear position, due to their precision, reliability, and ability to operate in harsh environmental conditions [1,2]. They are typically deployed in measuring instruments where the accuracy of displacement or distance measurement is crucial, for example in thickness gauges, micrometers and other measuring tools [3], and can be used to monitor and control the positions of moving parts in industrial machines, such as pistons, shafts, and guides, or to control the positions of valves, trolleys, robot arms and other components. This allows for precise adjustment of production processes and increased machine efficiency [4]. ...
This paper presents the procedure for determining the upper bound on absolute error (UBAE) for linear variable differential transformer (LVDT) sensors without inter-winding capacitance. This procedure is based on the results of a parametric identification of the sensor, from which the coefficient values of the corresponding transfer function are obtained. The UBAE is then determined by a simulation experiment using dedicated computational software. The error value and the shape of the input signal, which is constrained in magnitude, are determined. The calculations and additional validation of the procedure presented in this article are carried out using the MathCad 5.0 program. As the basis for the proposed procedure, we review issues related to the modelling of LVDT sensors without inter-winding capacitance. The solutions presented here can be used to determine the UBAE, which can then be used to assess the accuracy of these types of sensor and their mutual comparability in terms of dynamic accuracy.
... • Linear Variable Differential Transformers (LVDTs): This passive displacement measuring system may be placed on the sides between the Target Assembly back plate and the HFTM/STUMM, as widely used in many mechatronic systems in particle accelerators [44]. Although radiation campaigns shall be performed to verify their resistance when exposed to the hundreds of MGy/fpy expected around the Target Assembly and HFTM/STUMM. ...
The IFMIF-DONES Facility is a unique first-class scientific infrastructure whose construction is foreseen in Granada, Spain, in the coming years. Strong integration efforts are being made at the current project phase aiming at harmonizing the ongoing design of the different and complex Systems of the facility. The consolidation of the Diagnostics and Instrumentation, transversal across many of them, is a key element of this purpose. A top-down strategy is proposed for a systematic Diagnostics Review and Requirement definition, putting emphasis in the one-of-a-kind instruments necessary by the operational particularities of some of the Systems, as well as to the harsh environment that they shall survive. In addition, other transversal aspects such as the ones related to Safety and Machine Protection and their respective requirements shall be also considered. The goal is therefore to advance further and solidly in the respective designs, identify problems in advance, and steer the Diagnostics development and validation campaigns that will be required. The present work provides an overview of this integration strategy as well as a description of some of the most challenging Diagnostics and Instruments within the facility, including several proposed techniques currently under study.
... Sensor instruments typically consist of signal conversion, signal conditioning, and display unit blocks, each of which is needed to achieve error-free measurements. In Ref. 15, the design of a signal conditioning circuit using an amplifier, filter, and other elementary components is reported. The output of an LVDT is conditioned using modulation and demodulation circuits to obtain a calibrated result. ...
Background: Displacement is often used as an indirect indicator for monitoring multiple parameters, i.e. force, velocity, acceleration, and weight, making it an important variable for the measurement and control of processes. Sensors such as Linear Variable Differential Transformers (LVDTs) play a primary role in the design of any displacement measuring instrument. Calibration of an instrument is carried out to produce accurate results from the measuring instrument.
Methods: The objective of this study is to calibrate the output of LVDT by designing a signal conditioning circuit so as to extend the linearity range of the sensor to 100% of the full scale input range, and also allows the measurement technique to adapt to variations in the physical parameters of the LVDT, the supply frequency, and the temperature. An optimized neural network is trained to produce linear and adaptive output from the raw data obtained from LVDT. Optimization is achieved by choosing the best neural network algorithm, number of hidden layers and transfer function of neurons which produce the least mean square error. The optimized neural network algorithm is implemented on a Field Programmable Gate Array (FPGA) chip for testing and validation in real life.
Results: Experimental results show that the proposed technique was able to extend the linearity of LVDT and make the output adaptive for variations in physical parameters of LVDT, supply frequency and temperature.
Conclusions: Accurate measurement of displacement is essential in many process applications, and a good calibration technique is required to produce accurate measurement. The presented calibration technique using optimized neural network algorithms has produced reliable measurements as desired.
... Basic design considerations for LVDTs are given in [50]. The output signal of LVDT sensors is often processed by PSD (phase-sensitive detector = synchronous rectifier, lockin amplifier), but ratiometric processing is used more often [51,52]. Synchronous demodulation is less noisy and is more resistant against interference, but requires phase corrections. ...
Magnetic position sensors are popular in industrial and automotive applications since they are robust, resistant to dust and oil and they can be cheap. However, precise magnetic position sensors can achieve 0.015 % accuracy and 10 nm resolution. The maximum achievable range is about 20 m. DC magnetic position sensors are using a permanent magnet as a field source. As a field sensor, magnetoresistors are often used instead of traditional Hall sensors. Eddy current sensors work also with non-magnetic conduction targets. Magnetostrictive sensors are based on the time-of-flight of the elastic wave excited in the magnetostrictive material. The sensors can be several meters long and their applications range from level meters to hydraulics. Magnetic trackers and long-range position sensors utilize AC field sources, which are detectable from distances up to 20 m. Compared to optical instruments magnetic trackers do not need direct view. Their applications include surgery, mixed reality, and underground and underwater navigation.
... Other techniques are based on the use of a temperature-sensitive device to compensate the temperature effect. (27)(28)(29) However, the temperature-sensitive device requires similar behavior to the transducer, which is inconvenient and unsuitable for commercial transducers. Approaches using the output signal of a transformertype transducer to determine the temperature effect have recently been presented. ...
... In the light of these, Masi et al. chose a three-parameter sine-fit algorithm to regenerate the output signal of LVDT and ratiometric algorithm to read the exact position of the core. These techniques allows them to tune the device locally and read the position of the core with aa accuracy of a few micrometers even low-signal-to noise ratio (Masi et al., 2014). ...
... The conditioning module has nearly 45nm/C position drift after room temperature of 25C degree. They said that, for the radioactive environment, standard LVDT signal conditioning modules are not effective and sufficient (Masi et al., 2014). introduces (Coppo, Dongiovanni, & Negri, 2007). ...
In present study, a sensor, Accuciser, is presented to know the position of sliding valves which have ferromagnetic or diamagnetic guide. The main objective is to develop a sensor, which has low cost and high resolution, that measures the displacement of engine valves or SCR injectors which are used in especially in the automotive industry. For now, the position of the valves, which are using in propulsion systems, or SCR injector cannot be known with a signal from an analog sensor. Instead of analog sensor, the mapping is used from experimental data. However, this mapping gives inaccurate results due to driving style or usage of the system. After seeing the gap in these systems, the sensor was developed, and it fulfils this gap. The sensor is developed based on Faraday’s Law of Induction which was discovered by Michael Faraday in 1830. The sensor consists of two coils and one coil located on top of the other. The most important property of the proposed sensor is working with a direct current. In fact, if the valve is actuated by an electromagnetic force, there is no power consumption on the sensor. The experimental results, for the latter property, are corroborated by theoretical calculations. The output of the sensor is directly proportional to the displacement of the core and it has high signal-to-noise ratio because of the nature of magnetism. The results show that using Accuciser, the proposed sensor, to monitor valve displacement gives more reliable results than current technology.
... The reason that EFPI sensors are designed and used to measure the shrinkage of mortar specimen is the high resolution compared with commercially available LVDTs. LVDT displacement sensor operates on electromagnetic coupling principles between the primary coil and the two secondary coils in a friction-free structure, therefore, it has theoretically infinite resolution [54]. However, in practice, its resolution is limited by the external output electronics, the physical suspensions, the signal-to-noise ratio of the system, or in one word, the data acquisition system [55]. ...
Sliding and displacement instruments based on extrinsic Fabry-Perot interferometer (EFPI) are proposed to simultaneously monitor shrinkage and the coefficient of thermal expansion (CTE) of mortar specimens at early stages. Mortar specimens with three water cement ratios are tested. The effect of surface roughness on the shrinkage of mortar specimen is considered by using grooved stainless steel molds. The shrinkage from displacement sensors are compared with that from traditional linear variable differential transformer (LVDT). The CTE of mortar specimens is also measured with EFPI displacement sensor. Results indicate that both EFPI sliding and displacement sensors are capable of measuring shrinkage of mortar beam with nanometer resolution, which is higher than micrometer resolution from LVDT. The shrinkage of mortar is dependent on water cement ratio, curing age and surface roughness. The evolution of the CTE of mortar specimens over curing time is successfully measured with EFPI displacement sensor.
... The working principle of LVDT is detailed in [1]. Many applications require reading uncertainty as low as a few micrometers and also may require the transducer to be located in harsh and crammed environments, for instance, the case of the Large Hadron Collider (LHC) collimators position survey system [2]. In such cases, locating the reading electronics far from the transducer might tamper the accuracy. ...
A novel Application-Specific Integrated Circuit (ASIC) based signal conditioning system for closed loop control of Linear Variable Differential Transformer (LVDT) for sensor interface application is presented in this paper. The LVDTs are used for measuring linear displacement in industrial, military, aerospace, sub-sea, downhole drilling, nuclear power and process control applications. The signal conditioning is achieved through an ASIC-based digital signal processing unit. The existing commercially available Integrated Circuits (ICs) for LVDT signal conditioning are mostly analog and additional external circuitry is required for processing. The proposed system is a digital implementation of the LVDT signal conditioner with a better dynamic response and linearity through closed loop control. A unique feature of this ASIC is the use of synchronous demodulation technique using ADC sampling, reducing the complexity involved in conventional AM demodulation circuits. One of the major advantages of digital implementation is that the system can be reconfigured through external supervisory control. In this implementation, this is enabled by a universal asynchronous receiver-transmitter (UART) interface. This makes the system suitable for a wide range of applications. The functionality of the system was verified through a Verilog implementation on ARTIX-7 Field Programmable Gate Array (FPGA). The ASIC design is implemented in SCL-180 nm technology with an area 1 mm X 1 mm and the power utilization is 285 \(\upmu \)W.
... A ratio-metric microcontroller based technique has been developed by Nandagopal and Boby [9] to measure a variable by using a differential inductive sensor in the form of digital signal which is clamed to be free from the effect of variation in the parameters such as excitation voltage, reference voltage, offset of the comparator of the microcontroller, etc. A radiation tolerant LVDT conditioning module has been developed by Masi et al. [10] using Commercial Off-The-Shelf (COTS) components. This technique consists of a three parameter sine-fit algorithm to reconstruct the signal from the LVDT secondaries where a ratio-metric formula is used to compute the value of the core absolute position. ...
The conventional LVDT is generally used as displacement transducer but has some limitations such as small linear range, measurement errors due to stray capacitance effect, electromagnetic interference effect, core loss effect etc. In the present work a modified LVDT type displacement transducer has been proposed in order to overcome these limitations of conventional LVDT. The proposed LVDT will consist of only two identical coils instead of three coils of conventional LVDT. This design does not require any excitation coil. In this design, two identical coils wound on a former made of ferromagnetic material act as displacement sensing inductive coils with specially designed movable core. The design has been analysed under three cases. It has been shown that the range of the displacement transducer is about 50% of the overall length of the sensor under two cases like conventional LVDT and is about 100% of the overall length of the sensor under the third case. So in the present work, a displacement transducer has been designed and tested experimentally considering only the third case with unlimited range equal to the entire length of the sensor. The transducer consists of an op-amp based differential inductance measuring circuit and an output instrumentation amplifier. The performance equations of this sensor under three cases and of the transducer under third case are derived in the paper. The experimental results reported in the paper are found to follow the derived equations with very good linearity and repeatability.
... The output signal produced indicates direction of core movements from the centre position [4]. These devices have capabilities of contact-less sensing, tolerance against radiations, infinite resolution, good linearity and are cost effective [5]. Researchers have been showing keen interest in studying and analysing performance of LVDT's due to their vast engineering applications. ...
