Linear position transducer

The most suitable type of glass cell for use with gas-liquid mixtures is illustrated in Fig. 5.9. The gas component is dried and degassed in the high-pressure apparatus shown in Fig. 5.8. The gas-liquid mixture is prepared in the autoclave in Fig. 5.9(a). The autoclave is flushed with the gas at atmospheric pressure. Then a defined amount of the degassed liquid is introduced into the autoclave with a syringe fitted with a hypodermic needle. The autoclave is closed immediately, and the gas is forced into the autoclave at the lowest pressure used later in the experiments. During this process the bronze bellows has to be kept in a contracted position which is controlled by linear-position transducers and regulated by the flow of standard-pressure liquid into the bellows. 

Linear position transducers The simplest form is a linear potentiometer, where the position of the slider is proportional to the output voltage. Linear variable differential transformers (LVDls) move a metal core between primary and secondary coils to produce a voltage proportional to core position. 

Linearity, in measurement systems, 1879 Linear models, 2524-2525 Linear optimization, see Linear programming Linear position transducers, 1902 Linear programming (LP), 1725-1726, 2055-2056, 2524-2538 and additivity, 2525-2526 applications of, 2538 computer software for, 2534-2536 discrete optimization, see Discrete optimization... 

The exact shot size delivered to that point wiU have been determined by the shot size. This starting position is accurately controlled by a linear position transducer. The screw will have arrived at that preinjection point by turning the screw at a set RPM and under back pressure which the operator establishes as control set points. 

Linear position Linear motion is typically driven by the use of lead screws, ball screws, or worm drives with ranges from less than a 25 mm to over 6 m. Linear sensors for position feedback in the lower range include LVDTs, magnetic, and optical encoders. For longer strokes, the linear feedback devices include encoders and magnetostrictive position transducers. Optical encoders are practical up to 2 m. Magnetostrictive position transducers can be used up to 20 m. 

Position transducers are also very important in the plastics industry. Both linear and rotary displacement sensors are widely used. In injection molding, screw position for shot size and cushion must be very accurately measured. Mold open and close positions as well as ejector plate travel are also controlled with input from linear position sensors. Generally, it is recommended that linear position sensors provide an accuracy of better than 0.01%, a response time of less than 1 ms, and good vibration resistance [9]. 

Magnetostrictive linear displacement transducers measure the time it takes for a sonic pulse to travel Ifom a fixed source to a variable position. These newer devices are very accurate and are contact-less, offering the potential of long fife [9]. 

Fig.5 Example of histogram presentatioa The lower picture is a schematic representation of the monitored component with Uie position of the transducers (1-4). The higher window is the total AE counts vs linear location representation of the located AE sources...

The core - flood apparatus is illustrated in Figure 1. The system consists of two positive displacement pumps with their respective metering controls which are connected through 1/8 inch stainless steel tubing to a cross joint and subsequently to the inlet end of a coreholder 35 cm. long and 4 cm. in diameter. Online filters of 7 im size were used to filter the polymer and brine solutions. A bypass line was used to inject a slug of surfactant solution. Two Validyne pressure transducers with appropriate capacity diaphragms are connected to the system. One of these measured differential pressure between the two pressure taps located about one centimeter from either end of the coreholder, and the other recorded the total pressure drop across the core and was directly connected to the inlet line. A two - channel linear strip chart recorder provided a continuous trace of the pressures. An automatic fraction collector was used to collect the effluent fluids. 

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 ... 

To make sure that upon the pressure change to be recorded the intensity of the interference pattern on the diode stays within the linear range, the interference pattern can be shifted making use of the arbitrary phase in Eq. (4). In practice the phase shift is provided by changing the position of mirror 2 (Fig. 2) via a piezoelectric transducer. 

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 displacement transducers (LVDTs) which measure the absolute punch positions must also be carefully calibrated. This is particularly important when conducting studies which require accurate in-die tablet thickness measurements. Like the punch load cells, the calibration of the LVDTs are also performed in situ using a reference displacement transducer. Statistical analysis has shown that the displacement versus voltage relationship may not be linear over the full range of some transducers, and could be better described by a third-order polynomial. However, over smaller ranges, the relationship is adequately linear (24). These effects should be taken into account for a particular experiment or application as they could propagate error into in-die tablet thickness measure and subsequent. solid fraction calculations. Typically, calibration for both load cells and transducers are conducted once or twice annually. 

To calculate shear stress, shear rate and melt viscosity, the melt pressure and piston velocity must be monitored. The former is measured using a 0 to 20,000 psi pressure transducer mounted in the rheometer barrel just above the capillary. A linear potentiometer is used to monitor piston position during the test. Utilizing the piston displacement data and the HP real time clock, the piston velocity is calculated. 

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