Variable differential transformer

Linear-Variable-Differential-Transformer and Reluctive Pressure Transducers. In ahnear-vatiable-differential-transformer (LVDT) pressure transducer, the pressure to be measured is fed to a Bourdon tube or diaphragm. The motion of this element is transferred to the... 

Inductive Displacement Sensors and Linear Gaging Sensors linear variable differential transformer principle Micro-Epsilon transSENSOR... 

A TMA analyser will need to measure accurately both the temperature of the sample, and very small movements of a probe in contact with the surface of the sample. A typical analyser, as illustrated in Figure 11.20(a) and (b), uses a quartz probe containing a thermocouple for temperature measurement, and is coupled to the core of a linear variable differential transformer (LVDT). Small movements at the sample surface are transmitted to the core of the LVDT and converted into an electrical signal. In this way samples ranging from a few microns to centimetre thicknesses may be studied with sensitivity to movements of a few microns. For studying different mechanical properties the detailed construction of the probe will vary as is illustrated in Figure 11.20(c). 

Linear-variable-differential-transformer (LVDT) transducers, 20 652-653 Linear velocity, exponents of dimensions in absolute, gravitational, and engineering systems, 8 584t Lineatin, 24 473 Line-block coders, 7 691 Line-edge roughness (LER), 15 181 Line exposures, in photography, 19 209-210 Linen... 

LVDT—linear variable differential transformer, A/D—analogue to digital, VDU—visual... 

An associated type of transducer is the Linear Variable Differential Transformer (LVDT) which is essentially a transformer with a single primary winding and two identical secondary windings wound on a tubular ferromagnetic former. The primary winding is energised by an a.c. source (see Fig. 6.13). 

FlO. 6.13. Linear variable differential transformer (LVDT) using C-type Bourdon tube as... 

As the density of the liquid increases the float also rises and lifts the chain. The float continues to ascend until the additional weight of the chain raised equals the additional buoyancy due to the increased density. The reverse occurs when the density of the liquid is reduced. The position of the float is detected by a linear variable differential transformer (LVTD) in which the movement of the ferromagnetic core of the displacer changes the inductance between the primary and secondary windings of a differential transformer (see also Fig. 6.13). Such meters... 

A device which provides accurate position indication throughout the range of valve or control rod travel is a linear variable differential transformer (LVDT), illustrated in Figure 6. Unlike the potentiometer position indicator, no physical connection to the extension is required. 

The position can also be determined in a resistive or voltage mode. In the resistive mode, a current is sent to the center tap and to one of the end terminals, whereas the resulting voltage drop is measured by the transmitter. A potentiometer has an infinite resolution. Linearity for a precision rotary potentiometer can be as good as 0.25%. However, due to linkages and gears, the linearity for the entire assembly usually is about 0.5-1%. A linear variable differential transformer (LVDT) is mostly used in linear motion applications and also inside some pressure transmitters (Figure 3.131). 

The operating principle of an (linear variable differential transformer) LVDT-type sensor. 

The operation of proximity sensors can be based on a wide range of principles, including capacitance, induction, Hall and magnetic effects variable reluctance, linear variable differential transformer (LVDT), variable resistor mechanical and electromechanical limit switches optical, photoelectric, or fiber-optic sensors laser-based distance, dimension, or thickness sensors air gap sensors ultrasonic and displacement transducers. Their detection ranges vary from micrometers to meters, and their applications include the measurement of position, displacement, proximity, or operational limits in controlling moving components of valves and dampers. Either linear or angular position can be measured ... 

Mechanical properties of the composite materials were tested by a hydraulic-driven MTS tensile tester manufactured by MTS Systems Corporation, Minneapolis, Minnesota. A strain-rate of 5x 10 5 s 1 was used. During deformation, the linear actuactor position was monitored and controlled by a linear variable differential transformer (LVDT), while strain was measured using MTS-brand axial and diametral strain-gauge extensometers. The axial extensometer serves to measure the tensile deformation in the direction of loading while the diametral extensometer serves to measure the compressive deformation at 90° to the loading axis due to Poisson s contraction. All tensile tests were performed at 23 °C and in accordance to ASTM D3518-76. 

A cutaway drawing of the rotating-cylinder reactor is shown in Fig. 35. The mechanical aspects of the reactor system were designed to provide temperature control, fluid containment, and process measurements. The apparatus consists of a stainless steel (SS) holder and glass cylinder in which rides an SS piston, sealed by two Viton O-rings. Piston movements is monitored by a linear variable differential transformer (type 250 HCD, Schaevetz Engineering) attached to the piston and fixed relative to the cylinder. 

Linear variable differential transformer (LVDT, Fig. 2) is a device that produces voltage proportional to the position of a core rod inside a cylinder body. It measures displacement or a position of an object relative to some predefined zero location. On tablet presses, LVDTs are used to measure punch displacement and in-die thickness. They generally have very high precision and accuracy, but there are numerous practical concerns regarding improper mounting or maintenance of such transducers on tablet presses. 

The instruments have a furnace, and mostly a linear variable differential transformer (LVDT) to produce an electrical signal from a linear movement. An additional unit controls the force applied. Special attachments allow the same instrument to work in different modes such as elongation, compression, penetration, or tension. 

A dilatometer constructed by Sauer is shown in Fig. 45. The sensing element is a linear variable differential transformer, whose rectified output is recorded directly. A pivot arm connects the transformer (A) to the bearing arm (B) and a micrometer screw allows for calibration and adjustment of the transformer. By adjustment of the compensating screw, the pivot arm can be moved so that the contact point (B) is exactly one sample length from the fulcrum. Temperatures above and below ambient can be obtained by circulating gas round the specimen. 

Tensile and compressive tests were performed at room temperature with a tensile testing machine (DY25, Adamel-Lhomargy). For the tensile tests, strain measurements were performed with an extensometer (EX-10) at a strain rate of 3.3 x 10-4 s-1, using ISO-60 standard specimens. Samples of dimension 20 x 12 x 6 mm were deformed in a compression cage between polished steel plates. The nominal strain was determined by averaging the results from two linear variable differential transformer (LVDT) transducers. The strain rate used was 8.3 x 10"4 s-1. 

Instrumentation - load cell, linearly variable differential transformer (LVDT), clip gage, etc. 

A widely used sensor in physiological research and clinical medicine is the linear variable differential transformer (LVDT). It is used to measure pressure, displacement and force (Reddy and Kesavan 1988). The LVDT is composed... 

Allard E M 1962 Sound and pressure signals obtained from a single intracardiac transducer IRE Trans. Bio-Med. Electron. BME-9 74-7 van Citters R L 1966 Mutual inductance transducers Methods in Medical Research vol XI, ed R F Rushmer (Chicago Year Book), pp 26-30 Reddy N P and Kesavan S K 1988 Linear variable differential transformers Encyclopedia of Medical Devices and Instrumentation ed J G Webster (New York Wiley) pp 1800-6... 

Thermal expansion coefficients are measured with a dilatometer, which is essentially a high-temperature furnace from which a rod sticks out (Fig. 4.9). One side of the rod is pushed against the sample for which the thermal expansion is to be measured, and the other side is attached to a device that can measure the displacement of the rod very accurately, such as a linear variable differential transformer or LVDT. In a typical experiment, the sample is placed inside the furnace and is heated at a constant rate, while simultaneously the displacement of the push rod is measured. Typical curves for a number of ceramics and metals are shown in Fig. 4.4. 

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