A Review of Gas-operated Piston Gauges

This paper presents a new device to automatically handle a large number of weights for the calibration of a pressure gauge. This newly invented weight-handling device is made for use in conjunction with a commercial oil pressure balance. Although the pressure balance is essential as a calibration tool, its use has been generally tedious and labour intensive for a long time. In particular, the process of loading a different combination of weights on the top of a piston requires repetitious manual handling for every new measurement. This inevitably leaves the operator fatigued, and sometimes causes damage to the weights due to careless handling. The newly invented automatic weight-handling device can eliminate such tedious, error-prone and wear-inducing manual weight manipulation. The device consists of a stepping motor, a drive belt, a solenoid valve, three weight-lifting assemblies and three linear-motion guide assemblies. The weight-lifting assembly is composed of a pneumatic actuator, a solid-state switch and a metal finger. It has many advantages compared with the commercial automatic weight-handling device. Firstly, it is not necessary to lift all the weights off the piston in the weight selection process, as it is in the case of the commercial device. Thus it can prevent a permanent deformation of the weight carrier. Secondly, this new device can handle a larger number of weights than the commercial one. This is because the new device adopts a different method in retaining the remaining weights in place. Another advantage of this new device is that there is no possibility of the fingers touching the surface of the weights due to the oscillation of weights. Moreover it uses the general technology of a stepping motor, and is also made up of components that are easily obtainable in the market, thereby being very economical.

Section: Apparatusmentioning

confidence: 99%

New weight-handling device for commercial oil pressure balances

Woo¹,

Choi²,

Kim³

2005

“…Most commonly, gas-operated pressure balances are used for the generation or measurement of gauge and absolute pressures in the range 2 kPa to 10 MPa. However, they are also used for gauge pressure measurements from below 1 Pa [1] to above 100 MPa (section 7.2 of [2]), for the measurement of absolute pressures down to 10 Pa and below [3] and for differential pressure measurement at line pressure up to 20 MPa [4]. Gas-operated pressure balances can also be used as primary standards with the generated pressure traceable to measurements of mass, length and time or as reference standards traceable to another pressure standard.…”

Section: Introductionmentioning

confidence: 99%

Performance aspects of gas-operated pressure balances as pressure standards

Sutton

Fitzgerald

2009

In this paper, the aspects of gas-operated pressure balances that affect their performance are discussed. These aspects include both the features that make gas-operated pressure balances suitable for use as pressure standards and the factors that must be managed to achieve good performance. As key features, gas-operated pressure balances are pressure generators, have excellent relative short-term stability (∼5 × 10 −9 ) and long-term stability (∼1 × 10 −6 ), and can be used as primary standards. Factors to manage include harmonic oscillation of the piston in the cylinder, pressure balance temperature and operating height, and geometric imperfections. Three applications are used to illustrate the performance aspects of gas-operated pressure balances: a primary standard, a standard for differential pressure from <1 Pa to >1000 Pa and a standard for absolute pressure from <10 Pa to 10 kPa.

“…However, the complexity and the cost of these manometers, and the health concerns pertaining to mercury vapour make them less desirable for use in many calibration laboratories. As a substitute, a gas-operated pressure balance can be used for the calibration of low-pressure gauges [2].…”

Section: Introductionmentioning

confidence: 99%

New apparatus for calibrations in the range of 2 kPa absolute pressure

Woo¹,

Choi²

2005

Capacitance diaphragm gauges (CDGs) are precise electromechanical pressure sensors in which the displacement of a stretched thin metal diaphragm is detected by the measurement of a capacitance. These are very accurate gauges, and are frequently used as transfer gauges. To calibrate such accurate low-pressure gauges, precise mercury manometers have been used. However, complexity, concern about mercury vapour, and cost of mercury manometers have made it difficult to use these manometers in many industrial calibration laboratories. As a substitute, gas-operated piston gauges can be used for the calibration of such low-pressure gauges. However, the minimum pressure that is necessary to balance the tare weight, which generally corresponds to a pressure of several kilopascals, is a major obstacle. To reduce this minimum operating pressure, we adopted a variable bell-jar pressure method. To realize this method effectively, we developed a new mass-handling device that makes it possible to add or remove weights up to 200 g easily, with a resolution of 10 g, without breaking the vacuum during the calibration. This calibration system can be used to measure pressures from 100 Pa to 2 kPa in the absolute mode. In this paper, we also present the calibration results for two types of CDGs with full-scale ranges of 1330 Pa and 1000 Pa, respectively.