Dead-weight Tester Research Articles

Drift Corrected Seafloor Pressure Observations of Vertical Deformation at Axial Seamount 2018–2021

AbstractAxial Seamount is a seafloor volcano with frequent eruptions and periodic cycles of inflation and deflation. Seafloor pressure gauges monitor vertical deformation with time, but inherent instrumental drift complicates and biases geodetic interpretation. A drift corrected pressure recorder was deployed on Axial Seamount on 6 July 2018, at coordinates 45° 57.29′ North latitude, −130° 0.56′ East longitude, depth 1,535 m. This system includes two independent quartz‐resonant pressure gauges, which nearly continuously observe the seafloor pressure. At regular intervals, the gauges are calibrated in situ with a modified deadweight tester at a pressure within 98% of the nominal seafloor pressure. Using the calibration data, the drift of each gauge has been modeled as a simple linear plus decaying exponential function of time. The two estimated linear sensor drift rates are 0.45 ± 0.12 and 0.36 ± 0.08 kPa/year; the modeled sensor drift represents a significant error if uncorrected. The standard deviations of the drift model residuals are of order 0.06 kPa or 6 mm depth equivalent. Once calibrated, the difference between the two seafloor pressure timeseries exhibits a RMS deviation of ±6 mm at the 90% confidence limit and a linear trend less than 1 mm/year. A time series from July 2018 to December 2021 tracks the inflation of Axial Seamount with differing inflation rates over different time intervals.

Comparison of Stress-Impedance Effect in Amorphous Ribbons with Positive and Negative Magnetostriction.

The SI (stress-impedance) effect in amorphous ribbons with varying magnetostriction was investigated. Iron- and cobalt-based ribbons with different magnetostriction coefficients were put under tensile stress in a dead weight tester and the impedance change was investigated in function of applied stresses. Significant differences of characteristics are presented. Stress-impedance analog of Villari reversal point was observed. The reversal point showed driving current frequency dependence, in which this point manifests for different stress values. Based on the obtained SI characteristics and magnetoelastic hysteresis, the most appropriate stress-sensing material was selected for development of precise small forces sensor.

Design, development and performance evaluation of pressure sensor using eddy current displacement sensing coil

PurposeThe conventional strain gauge type pressure sensor suffers in static testing of engines due to the contact transduction method. This paper aims to focus on the concept of non-contact transduction-based pressure sensor using eddy current displacement sensing coil (ECDS) to overcome the temperature limitations of the strain gauge type pressure sensor. This paper includes the fabrication of prototypes of the proposed pressure sensor and its performance evaluation by static calibration. The fabricated pressure sensor is proposed to measure pressure in static test environment for a short period in the order of few seconds. The limitations of the fabricated pressure sensor related to temperature problems are highlighted and the suitable design changes are recommended to aid the future design.Design/methodology/approachThe design of ECDS-based pressure sensor is aimed to provide non-contact transduction to overcome the limitations of the strain gauge type of pressure sensor. The ECDS is designed and fabricated with two configurations to measure deflection of the diaphragm corresponding to the applied pressure. The fabricated ECDS is calibrated using a standard micro meter to ensure transduction within limits. The fabricated prototypes of pressure sensors are calibrated using dead weight tester, and the calibration results are analyzed to select the best configuration. The proposed pressure sensor is tested at different temperatures, and the test results are analyzed to provide recommendations to overcome the shortcomings.FindingsThe performance of the different configurations of the pressure sensor using ECDS is evaluated using the calibration data. The analysis of the calibration results indicates that the pressure sensor using ECDS (coil-B) with the diaphragm as target is the best configuration. The accuracy of the fabricated pressure sensor with best configuration is ±2.8 per cent and the full scale (FS) output is 3.8 KHz. The designed non-contact transduction method extends the operating temperature of the pressure sensor up to 150°C with the specified accuracy for the short period.Originality/valueMost studies of eddy current sensing coil focus on the displacement and position measurement but not on the pressure measurement. This paper is concerned with the design of the pressure sensor using ECDS to realize the non-contact transduction to overcome the limitations of strain gauge type pressure sensors and evaluation of the fabricated prototypes. It is shown that the accuracy of the proposed pressure sensor is not affected by the high temperature for the short period due to non-contact transduction using ECDS.

Electro-Pneumatic Control System with Hydraulically Positioning Actuator Motor

A compressibility of the actuating fluid of a pneumatic drive (compressed air) leads to significant landing of the pneumatic cylinder piston at the time of stop and hold of the load, a constant component of which can fluctuate significantly for the holding period. There are a lot of factors, which have a significant impact on the landing value of piston. Those are: an initial position of the piston at its stop, which determines the volume of the an active area of the piston, a value of the constant load component at the time of stop and its variation for the holding period, a transfer coefficient of the position component of the load, an active area of the pneumatic cylinder piston, as well as reduction in atmospheric pressure, which can significantly affect the operation of the control systems of small aircrafts flying at high altitudes. To reduce the landing value of piston due to changing value of the constant load component for its holding period, it is proposed to use a hydraulic positioner, which comprises a hydraulic cylinder the rod of which is rigidly connected to the rod of the pneumatic cylinder through the traverse, a cross-feed valve of the hydro-cylinder cavities with discrete electro-magnetic control, and adjustable chokes. A programmable logic controller provides the hydraulic positioner control. At the moment the piston stops and the load is held the cross-feed valve overlaps the hydro-cylinder cavities thereby locking the pneumatic cylinder piston and preventing its landing. With available pneumatic cylinder-controlled signal the cross-feed valve connects the piston and rod cavities of the positioner hydro-cylinder, the pneumatic cylinder piston is released and becomes capable of moving. A numerical estimate of landing of the pneumatic cylinder piston and its positioning quality is of essential interest. For this purpose, a technique to calculate the landing of piston has been developed taking into consideration that different factors, which determine operation conditions of the pneumatic cylinder, have the impact on it. Experimental investigation of piston landing was conducted using the pneumatic cylinder with piston and rod diameters of 32 and 16 mm, respectively, at operating pressure of 0.8 MPa. With a vertical arrangement of the pneumatic cylinder axis, the control weights of a dead-weight pressure-gauge tester created a constant component of the load and its variation, and an indicator with resolution of 0.05 mm estimated a landing value. The article shows the calculated data of piston landing, which are in good compliance with the experimental results. To substantially reduce the piston landing for the holding period of the load varying in value and sign was designed a hydraulic positioner of pneumatic cylinder piston, and its operation quality is studied on the physical layout of electro-pneumatic control system operating in the discrete and tracking modes. For control system service, work programs of the programmable logic controller integrated in the control circuit of the hydraulic positioner in discrete mode, and, as a digital discriminator, in tracking mode are developed. In conclusion as a result of the research activities the article estimates the impact of factors on the quality of the load position at the time of its hold and notes a high efficiency of the hydraulic positioner of pneumatic cylinder piston both in discrete mode and in tracking one.

An Examination of the Uncertainty of Industrial Deadweight Testers Used for Pressure Calibrations in Different Environments

The industrial deadweight tester (IDWT) is a dead weight pressure gauge that is designed, built, and calibrated to be used without having to make corrections or calculate pressure. In practice, the...

Pressure transmitter accuracy

This paper discusses the key causes of calibration drift in pressure transmitters and procedures for calibrating pressure transmitters to ensure their accuracy. Calibrating pressure transmitters involves adjusting the potentiometers in the sensor that controls the zero (lowest pressure at which a transmitter is calibrated) and span (the range of pressure the transmitter is to indicate) of the transmitter. The initial or bench calibration of pressure transmitters involves using a constant pressure source such as a deadweight tester. Once the transmitters are installed, temperature, pressure, humidity, vibration, maintenance activities, and normal aging can degrade their accuracy. Transmitter accuracy can also be degraded by transmitter sensing lines, when the water in a sensing line reference leg boils off, when non-condensable gases in the reference leg dissolve, and when voids, blockages, freezing, or leakage occur in sensing lines. On-line calibration techniques enable plants to avoid these accuracy problems by monitoring the output of an individual transmitter.

A Double-Primary Dead-Weight Tester for Pressures (35-175) kPa in Gage Mode.

Primary pressure standards in the atmospheric pressure range are often established using mercury manometers. Less frequently, controlled-clearance dead-weight testers in which one component (normally the piston) has been dimensionally measured have also been used. Recent advances in technology on two fronts i) the fabrication of large-diameter pistons and cylinders with good geometry; and ii) the ability to measure the dimensions of these components, have allowed some dead-weight testers at NIST to approach total relative uncertainties (k = 2) in dimensionally-derived effective areas near 5 × 10−6. This paper describes a single piston/cylinder assembly (NIST-PG201WC/WC) that serves as both a primary gage in which both piston and cylinder are measured dimensionally and a controlled-clearance primary gage (employing the Heydemann-Welch method). Thus it allows some previous assumptions about the modeling of dead-weight testers to be checked. For the gage described in this paper the piston/cylinder clearance obtained from the two analyses have relative differences of 4 × 10−6 to 7 × 10−6 over the pressure range 35 kPa to 175 kPa. Some implications of these results will be discussed. From the dimensional characterizations and auxiliary measurements we have determined that the effective area for this gauge at 20 °C is: Aeff,20=1961.0659mm2(1+3.75×10−12P/Pa+3.05×10−12PJ/Pa),where P is the system pressure and PJ is a control pressure. The estimated relative uncertainty in effective area is 8.2 × 10−6 +1.4 × 10−11 P/Pa (k = 2). The temperature coefficient for the area was measured and found to be (9.06 ± 0.04) × 10−6/K. Thus using the gage at a reference temperature of 23 °C yields an effective area: Aeff,23=1961.1192mm2(1+3.75×10−12P/Pa+3.05×10−12PJ/Pa),with almost no increase in the uncertainty over that at 20 °C.

Long-term stability and performance characteristics of crystal quartz gauge at high pressures and temperatures

Good long-term stability of high precision quartz pressure sensors is necessary for various applications ranging from pressure transient analysis to permanent monitoring systems for optimal reservoir management in the petroleum industry. A crystal quartz gauge (CQG(1 )) is a dual-mode, thickness-shear, quartz pressure sensor that has been used in oil field services for the past 8 years. High accuracy, resolution, and fast response time of this sensor enable a reliable estimate of formation permeability and oil/water interfaces in reservoirs that help reduce the overall cost of oil and gas production. The sensing resonator characteristics can be described in terms of equivalent circuit parameters (motional resistance and capacitance), resonator-Q and the short-term frequency stability of both the B- and C-modes of vibrations at various temperatures. The pressure reading errors of manufactured gauges are less than 8.89 kPa (1 psi) (plus 0.01% of the reading because of the uncertainty of the dead-weight tester). The pressure resolution is better than 20.7 Pa (0.003 psi) over a 1-s gate time. An extremely effective dynamic compensation algorithm yields corrected pressure readings with a very fast response time as short as a strain-gauge-based pressure transducer while retaining the high performance of a quartz gauge. Recent long-term stability tests of CBGs show a negligibly small drift of the order of a few tenths of 1 psi (0.1 psi=689 Pa) at 103 MPa (15 kpsi) and 175 degrees C for a period of more than 1 yr. These results confirm that the CQG characteristics exceed the demanding specifications for both the well tests and permanent monitoring systems.

Characterisation of a 1 GPa piston-cylinder unit

The accurate determination of distortion coefficients for dead-weight testers operating at high pressures has been treated by many authors using various methods, contributing to a better understanding of uncertainties in high pressure metrology. This paper addresses the characterisation of a dead-weight tester in a unique mathematical approach incorporating the elastic distortions and fluid properties of the transmitting fluid. The system comprises a high pressure assembly operating at 400 MPa. The study of the system behaviour extends beyond the nominal operating pressure range up to 1 GPa. The integrity of the models developed is based on theoretical and experimental validations carried out on other gas and oil operated balances. Results presented show a clear deviation from the formerly adopted “typical” behaviour of balance assemblies, including values used to correct for the uncertainty of pressure generated.

Accuracy and reliability of disposable pressure transducers coupled with modern pressure monitors

To determine the bedside accuracy of direct patient pressure monitoring when used with new and clinically used disposable blood pressure (BP) transducers. Prospective study. Laboratory bench and critical care units in an adult and children's hospital. Seventy-five bedside patient monitors (25 Marquette Electronics, 25 Spacelab Medical, and 25 Hewlett-Packard), and 100 disposable transducers (50 from Utah Medical Products and 50 from Abbott Critical Care Systems [25 new, 25 clinically used of each manufacturer]) were tested. None. A +/- 2% accuracy requirement for bedside monitors and the +/- 3% American National Standards Institute accuracy standard for disposable BP transducers were used. To test the accuracy of the bedside monitors, a certified transducer simulator was used to apply 100 mm Hg to each bedside monitor. To test the accuracy of the disposable BP transducers, a very accurate (+/- 0.05%) pneumatic dead weight tester was used to apply pressures to the transducer. A digital power supply and a 6 1/2 digit voltmeter were used. The average output of the bedside monitors when 100 mm Hg was applied was 99.90 +/- 0.83 mm Hg, with the worst cases being 98 and 103 mm Hg. For all 100 disposable pressure transducers, the average output was 100.03 +/- 0.55 mm Hg, with the worst cases being 98.53 and 101.36 when 100 mm Hg was applied. There was no important difference in the accuracy of the transducers obtained from the two vendors nor whether the transducers had been used clinically. All disposable BP transducers tested were much more accurate than the American National Standards Institute standard for accuracy. Even the worst case transducers were twice as accurate as required by the American National Standards Institute standard. Only one bedside monitor was outside the +/- 2% accuracy range (103 mm Hg). Based on these findings, this author recommends that fixed calibration disposable transducers and fixed calibration bedside pressure monitoring systems be used. The clinical risks of air embolism and infection from the calibrating mercury manometer and the complexity of the calibration task are the overriding factors for making these recommendations.

Simultaneous hydrostatic pressure and temperature measurement employing an LP/sub 01/-LP/sub 11/ fiber-optic polarization-sensitive intermodal interferometer

A fiber-optic LP/sub 01/-LP/sub 11/ polarization-sensitive intermodal interferometer is proposed to simultaneously measure hydrostatic pressure and temperature using the same sensing element. In analogy to the case of strain sensing it was found that the experimental parameters T/sub P/ and T/sub T/ describing the 2/spl pi/ phase shifts in the interferogram are significantly different for the X- and Y-polarizations of two polarization modes. This represents a fundamental phenomenon which can be put to use for simultaneous two-parameter sensing. The results obtained are found to be in agreement with a recently developed Muller-Stokes formalism describing polarization effects in the case of two-mode interference by means of spatial Stokes parameters. Initial calibration of the two-parameter simultaneous pressure-and-temperature sensor has been performed up to 100 MPa using a primary pressure standard (deadweight tester Harwood DWT-35).< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Error Analysis of Time-Dependent Frictional Torque in Reciprocating Engines: Effect of Cylinder Gas Pressure

Errors in the cylinder gas pressure due to zero drift, and changes in sensitivity caused by thermal stresses were investigated. Five quartz-crystal pressure transducers, of different makes and designs, were used in a single-cylinder diesel engine to measure the cylinder gas pressure and determine the instantaneous frictional torque and frictional mean effective pressure. All pressure data were obtained by using calibration constants determined from a dead-weight tester at atmospheric conditions, according to the manufacturer's specifications. Errors in the pressure caused by steady and transient variations in the transducer temperature were investigated under simulated engine conditions. The calibration of the transducer which gave the best performance was made at elevated temperatures. A new calibration constant was determined. The error in the instantaneous frictional torque due to the calibration at atmospheric conditions was determined. Presented as a Society of Tribologists and Lubrication Engineers ...

Comparison of Pneumatic Pressure Tester and State Special Standard of Pressure for Pressure Difference

A comparison is reported of a deadweight pressure tester using gas lubrication and the liquidfilled primary pressure State standard, accepted in the Soviet Union. The comparison is within the pressure range of 0,02 to 4,0 kPa. The standard error of the tester was shown to vary within the range 0,08 to 0,30 Pa. This portable tester 300 × 190 × 290 mm is intended as a secondary, transfer, standard.

A Standard Pressure Source for Calibrating Physiological Pressure Transducers

In common with all measuring instruments, pressure transducers should from time to time have their performance checked. Sensitivity, together with zero offset checks, must be considered only an essential minimum, and for confidence in the results of these measurements it is also necessary to look at linearity and hysteresis. Of course, factors such as natural frequency and damping are also important in practice, but are more dependent upon the hydraulic arrangements associated with the transducer than any quality of the transducer itself that is likely to vary appreciably. Thus, the equipment to be described is concerned only with the ‘static’ measurements mentioned. Although a zero offset check is a simple matter, measurement of the other factors requires a pressure source that can be set to two accurately known values in addition to zero (relative to ambient), and temporarily to some value below ambient for checking hysteresis. Such tests can be carried out using liquid column type manometers, but they are not always convenient in a clinical environment. Moreover, the widely used mercury sphygmomanometer has only to be accurate to within k 2 mmHg to meet British Standard requirements, and unless properly maintained can be appreciably worse than this. The equipment to be described, based on the principle of the deadweight tester, is an attempt to overcome these problems.

The Design of a Pneumatic Pressure Reference Source with Automatic Control

The design of a pneumatic pressure reference source with automatic control is described. The design is based on the accuracy and reliability of the well known dead weight tester and a piston position transducer is incorporated with a precision pressure controller to form a closed loop system. A linearised analysis is used to show the complexity of the system dynamics and give some indication of the stability criteria. A prototype model was built, tested and the results are discussed. Conclusions are drawn that suggest the system is feasible and worthy of further development.

Diaphragm Pressure Transducer

A diaphragm pressure transducer has been developed for the purpose of separating a sample fluid from a hydraulic oil used in a dead weight tester. The diaphragm null position is determined by a commercially available magnetic sensing unit. The null position shifts systematically with absolute pressure, but the shift is reproducible and may be calibrated. With the output scheme utilized, the unit has a sensitivity of 0.00007 atm and a reproducibility of 0.0003 atm. The equipment has been used extensively at pressures up to 70 atm, but as designed should be operable to much higher pressures. The equipment described includes a small injector for refined pressure adjustments.

The Standardization of Durometers

Abstract The hardness test is one of the most useful and convenient physical tests which can be made on vulcanized rubber. It is easily made because the equipment can be simple, compact and portable. It is particularly useful in that the test sample may be a production article which can be put into service, undamaged, after the test. Consequently the test appears in the industry in several modifications, and the tester in diverse styles. Several more or less readily portable hardness testers are available commercially. The Shore Instrument and Manufacturing Co. has its line of Durometers, types A, B, C, D, etc.; Schopper, through Testing Machines, Inc., has marketed a tester similar to the Shore type A; the U. S. Gauge Co. has an instrument of the same type using the case of their pressure gage; the Firestone Penetrometer is another well-known tester of the spring-load type, as is the Adams Densimeter. At the present time the Society's Committee D-11 on Rubber Products is studying four portable hardness testers which are based on the specifications of the Standard Method of Test for Hardness of Rubber (D314-39), three of these being spring-operated instruments, the fourth, a dead-load type. In addition to the testers mentioned above, there is the Pusey-Jones Plastometer, which is a dead-weight hardness tester rather than a plastometer.