This paper presents characterization of diving-bell manometer in the gauge pressure range from -1.0 up to 3.0 kPa in the Croatian national pressure laboratory - Laboratory for Process measurement (LPM), located at the Faculty of Mechanical Engineering and Naval Architecture (FSB), University of Zagreb.
The work points out comparison of two independent methods for diving-bell effective area determination i.e. determination based on dimensional measurements as well as determination of the effective area by a pressure comparison method. The dimensional measurements were performed in the Croatian national length laboratory, also at FSB.
Determination of the effective area by the pressure comparison method was performed in LPM using a Physikalisch-Technische Bundesanstalt (PTB) Rosemount pressure transducer previously calibrated in PTB Braunschweig. From the results it can be seen that the difference in the effective areas obtained with the two independent methods is very small compared to the estimated effective area measurement uncertainties.

A new fully automated system for calibrating a pressure balance is described. The system consists of two automated pressure balances, a pressure controller, two air-operated constant volume valves, a precise pressure transducer, a device for measuring environmental condition, a computer and the program developed. In the system, one pressure balance is used as a standard and the other is calibrated and/or evaluated. To determine the equilibrium state between two pressure balances accurately, the cross-float measurement using the comparator method is performed. In this paper, the details of the system are described and the results obtained using the system are shown.

The pressure crossfloat is a well established method for comparing the output of piston gauges with various media. The crossfloat is the most common method for determining the area of a test piston-cylinder relative to a reference piston-cylinder. The traditional crossfloat procedure is a tedious manual process that is highly dependent on operator skill, patience and experience. Due to the need to access the masses to make small mass adjustments, operation is normally gauge mode only.
In order to meet a high demand for low pressure, gas operated piston gauge systems, DHI has designed and implemented a fully automated crossfloat system over the range of 9 kPa to 7 MPa. The intent of the system is to be able to perform unattended crossfloats to determine the test piston-cylinder performance characteristics and determine effective area in either absolute or gauge mode. The crossfloat station was put into regular operation in late 2006 and has exceeded the expectations of its designers.
The automation is made possible by the use of two automated mass handling systems and a low differential pressure transmitter used to determine the final equilibrium point between the two piston-cylinders.
This paper describes the design of the automated calibration system, the challenges of its implementation and the results of numerous crossfloats performed over six months of automated operation.

Low-pressure detection technology utilizing the field emission of carbon nanotubes (CNTs) is introduced. The use of an ionization gauge is a viable alternative method for measurements at low pressure levels, but their use is limited by such factors as the bulky size, high power consumption, x-ray radiation, heat and light generation, and outgassing associated with this type of gauge. To overcome the limitations of conventional ionization gauges, CNTs have been proposed as an electron source. The performance of a CNTbased low-pressure gauge, including the sensitivity, measurement range, and linearity, has been improved greatly by changing the structure of the electrodes. The sensor showed a linear pressure measurement range from 5·10^-7 to 10^-2 Torr. Furthermore, the service life of the CNT emitter could be extended greatly by modulating the pulse of the voltage with a 20 % duty ratio. However, the service life of the CNT-based sensor is especially short, particularly when it is used at relatively high pressure levels. Accordingly, a CNT array directly grown by thermal Chemical Vapor Deposition is proposed. An integrated emitter directly grown with a catalyst metal can provide a low turn-on field by reducing the distance between the grid and CNTs while providing a longer emission lifetime. The characteristics of the directly grown CNT array and the screen-printed CNT array are compared for possible use with a practical pressure sensor.

The METAS static expansion system was built in 2004 and has been extensively characterised during the last two years.
The system consists of four expansion stages allowing the generation of calculable pressures ranging from 5·10^-6 Pa up to 2000 Pa.
Uncertainty calculation yields a relative uncertainty of 0.001 (k=2) for the volumetric ratio of the expansion stage. The relative uncertainty on the pressure obtained after expansion is 0.003 above 10 Pa, it is still 0.01 at 2·10^-4 Pa.
Measurement of the accommodation coefficient of two SRG from 10^-5 Pa up to 0.1 Pa has shown no significant deviation of the accommodation coefficient over the full range of measurement and over a period of time of 18 months.