Absolute pressure transducer

Absolute pressure transducers, 20 657 Absolutes, in perfumes, 18 365 Absolute system of dimensions, 8 584 Absolute temperature scale, 24 283 Absolute viscosity, exponents of dimensions in absolute, gravitational, and engineering systems, 8 584t Absorbable sutures... 

The equipment used in all experiments consisted basically of a C02 cylinder, a 20-mL view cell with three sapphire windows for visual observations, an absolute pressure transducer (Smar LD 301) with a precision of 0.012 MPa, a portable programmer (Smar HT 201) for pressure data acquisition, and a syringe pump (ISCO 260D). The equilibrium cell contained a movable piston, which permitted pressure control inside the cell. Figure 1 presents schematic diagram of the experimental unit. 

Xenon Adsorption Experiments. Gaseous xenon was co-adsorbed onto the samples on a vacuum manifold the xenon equilibrium pressure was measured by an absolute-pressure transducer (MRS Baratron) capable of measuring pressure with accuracy 0.1 torr. The adsorption isotherms of the co-adsorbed xenon in the samples were measured volumetrically at 22 °C. 

A - solvent reservoir B - high pressure pump C - extraction vessel D - absolute pressure transducer E - electrical heating with temperature control system F - glass collector G - trap H - flow meter. 

The first range can be adequately handled with a simple mercury manometer. ( 1 ) However, absolute pressure transducers, such as the Baratron 200 Series manufactured by MKS Instruments, offer much greater accuracy over a wider pressure range.(8) If accurate and precise pressure measurements are commonly conducted on the vacuum line, the transducers are the sensors of choice. If not, mercury manometers are the economical alternative. 

Level. Level sensors that depend on a pressure difference between two points, one submerged and one in the vapor, are subject to the same installation considerations described for pressure measurement. The inferred level measurement is more accurate when determined by a differential pressure transducer using remote diaphragms than when calculated from the difference between two absolute pressure transducers due to errors from calibration and transducer drift. In either case, the measurement is affected by changes in the weight percent solids in the solution an increase in the liquid density would be interpreted as an increase in the level. Ultrasonic level sensors are not affected by the slurry density but are sensitive to fouling. 

Figure 7.3 Piezo-resistive absolute pressure transducer (principle).

The order of nuignitude of temperature gradients that are maintained in the isothermal block of Tian-Calvet type calorimeters is suitable for the requirements quoted above. Indeed, even if the absolute temperature of the isothemud block may shift with time, the difference of temperature between the reference and the sample cell that are inside the oppositely connected thermopiles is better than 0.000IK. The schema of the set-up is presented in figure 1. The porous solid or the powder are in the sample cell. The reference cell contains the pure liquid. The two cells are connected through two valves (1 and 2) to a manifold equipped with an absolute pressure transducer (lOOtorrs Baratron MKS). The manifold is connected to a vacuum pump through a capillary. Controlled leak valves may also be used. Between the... 

The two torque transducers, cylinder pressure transducer, liner absolute pressure transducer and two encoder signal were connected to a 12-bit high speed simultaneous sampling data acquisition system. Two National Instruments 6110E boards were used each having four analogue input channels and two 20 MHz timer/counter channels. Unlike most of the data acquisition boards the 6110E does not work in multiplex mode as each... 

Strain-gauge pressure transducers are manufactured in many forms for measuring gauge, absolute, and differential pressures and vacuum. Full-scale ranges from 25.4 mm of water to 10,134 MPa are available. Strain gauges bonded direc tly to a diaphragm pressure-sensitive element usually have an extremely fast response time and are suitable for high-frequency dynamic-pressure measurements. 

Pressure. Pressure so defined is sometimes called absolute pressure. The differential pressure is the difference between two absolute pressures. The most common types of pressure-measuring sensors are silicon pressure sensors, mechanical strain gauges, and electromechanical transducers. 

Absolute pressure instrument transducer, Statham 1.0 kPa, via a probe at the centre of the duct outlet. 

When no observable changes of pressure were observed (equilibrium), the catalyst was added by rotating the glass jar. The catalyst dissolved in 10-30 sec, depending on olefin and catalyst concentrations. The pressure drop was recorded as a function of time by the pressure transducer and a recorder. The reaction rate was determined by measuring the slope of the tangent to the curve of the pressure drop at the point corresponding to the desired H2-partial pressure and the vapor pressure of the reaction mixture. The variation between two independent rate determinations at the same conditions was always less than 10% of the absolute value. 

The vibrating cylinder version of this type of transducer employs a sensing element of the straight tube type and is similar to the vibrating cylinder density meter (Section 6.6.1). The cylinder is maintained in oscillation by a feedback amplifier/limiter combination and its frequency of oscillation varies with the pressure of the fluid within it, which alters the hoop stress on the cylinder. As with the vibrating wire, the frequency of oscillation increases with the fluid pressure. In order to be able to use the sensor for the measurement of absolute pressures, it is surrounded with a cylindrical housing and the annular space between the two is evacuated. Such sensors give excellent repeatability and have a relatively low temperature sensitivity. 

A classical volumetric adsorption apparatus equipped with absolute capacitance pressures transducers can be used for the estimation of adsorption isotherms in the pressure range 10-3 mbaradsorption measurements the carbon black samples are extracted with toluene and water/methanol (1 1) and after drying degassed overnight at 200 °C at a pressure below 10 4 mbar. The time allowed for equilibrium of each point of the isotherm is 5-90 min depending on the sample and the adsorbed amount. 

Let us first consider the case of a discontinuous, point-by-point procedure. An absolute or perfect equilibrium can of course never be attained, since it is limited by the fluctuations of (a) the adsorbent temperature, (b) the residual gas temperature, and (c) the baseline of the pressure transducer. As a consequence, after a certain time, the system is as close as it will ever get to true equilibrium. Nevertheless, this time may be relatively long (e.g. it may take hours to determine each point). The experimenter may then decide to be less demanding in order to save time. A convenient way to operate, which lends itself to automation, is the following ... 

We have built a prototype of an interferometric pressure transducer that was designed to be attached to a non-commercial room temperature sorption instrument [3] equipped with a differential membrane sensor (MKS, Baratron 220CD, full range 10 mbar, pressure resolution 0,15 % of full range value). An additional absolute pressure sensor (MKS, Baratron 220 CA) integrated into the set-up provides the average pressure in the manifold and... 

Absolute pressure at the downstream end of the core is also monitored. This output pressure is maintained by a sensitive, manual needle valve that withstands the major pressure drop of the experiment. Because this is a steady-state experiment and not a core-flood, the correct setting of this valve needs to be made very infrequently during the run after steady state has been reached. The three transducer readings are continually recorded on a chart recorder, noted graphically on a computer screen, and periodically written to disk by a dedicated personal computer. 

Redox experiments and ESR determination of Cu2+ were performed with a circulation all-glass apparatus equipped with a magnetically driven pump. The sample (0.2 to 1.0 g) was placed in a silica reactor equipped with a side ESR tube. All the samples before the redox cycles were treated in O2 at 773 K. The redox cycles consisted of (i) heating in He flow at 823 K for 2h, followed by evacuation at 773 K and heating in O2 at 773 K (ii) evacuation at RT followed by reduction with CO at 773 K (iii) evacuation at 773 K followed by a second treatment with O2 at 773 K. During the treatments (i) to (iii), the pressure of O2 or CO was monitored with a pressure transducer (MKS Baratron, sensitivity 1 Pa) until a nearly constant pressure was reached. All these measurements allowed the variation of the average oxidation number of copper to be followed. The acquisition or loss of electrons are expressed as e/Cu (number of electrons/total number of Cu atoms). At the end of treatments (i) to (iii), ESR spectra of Cu2+ species were recorded at RT. ESR measurements were carried out on a Varian E-9 spectrometer equipped with an on line computer. Absolute concentrations of... 

Some BPBs will be fabricated with a pressure transducer mounted at one end. The initial version of this sensor is about 3 mm in diameter and is sensitive to pressures along the axial dimension of the BPB. Future versions will be sensitive to lateral pressure, and may be mounted remotely from the BPB. The present full-scale absolute pressure range is 400 to 900 mmHg. This signal can be read out either AC or DC coupled. When DC-coupled, it reads the absolute pressure. Since ambient pressure varies with altitude changes, this offset can be accounted for by placing a reference sensor of the same type in the MCU, then subtracting off this baseline. 

Figure 4.4.5. DifFerential vapor-pressure apparatus. 100 ml Pyrex flasks connected (a) to a differential pressure transducer (c) with digital readout (d) and (b) to vacuum pump (e) and absolute pressure vacuum thermocouple gauge (f). The constant temperature in the water bath is maintained by a temperature controller (g). The transducer and cormecting glassware are housed in an insulated box (i) and kept at constant temperature shghtly above the measuring temperature by controller (j). Polymer solution and pure solvent (here water) are stirred by underwater magnetic stirrers (h). [Reprinted with permission from Ref. 66, Copyright 1989, American Chemical Society].

Direct measurement of the individual pressures and P2) to enable use of equation (3) necessitates accurate absolute calibration of the pressure transducers. A difficulty was that density differences of the oil and water phases affected the hydrostatic pressures within each transducer. Consequently the procedure adopted was to use the pressure transducer outputs for the pure oil/water system as the calibration points for subsequent runs with surface active agents present, as outlined in the following section. 

---