Name of Standard: National standard for gauge pressure in liquid medium
Code designation: ECM 170-2/01-018
Year of publication: 2001
Department: nr. 6013 CMI RI Brno
Guarantor: Ing. Richard Páviš
Number of CMC lines provided: 1
Mode | Range | Uncertainty (k = 2) |
Gauge pressure | 100 kPa – 500 MPa | 9 Pa + 2,3∙10-5∙p + 1,9∙10-13∙p2 |
(p is the value of the generated pressure in pascals)
CMC magnitudes are expressed in terms of expanded uncertainty using an expansion factor of k = 2 (coverage probability of approximately 95%).
It is a pressure balance based on the classic design of a piston rotating in an unsealed, cylindrical housing on which weights are loaded, i.e. the same principle as in ECM 170-1, only the working medium is oil (di-2-ethyl-hexyl sebacate). The basis is again a commercially available equipment from DHI. Through long-term theoretical and experimental work between 1995 and 2000, the team led by Mgr. J. Tesar managed to prepare the standard scientifically and technically for the announcement as a national standard, which was successfully carried out in 2001.
The basis of the primary group standard consists of five piston-cylinders with different nominal effective areas. By means of hydrostatic comparison, they are linked to the national standard of gauge pressure, negative gauge pressure and absolute pressure in the gaseous medium and successively to each other. Two piston pressure gauge bases with internal sensors for piston-cylinder temperature, piston-cylinder position, ambient temperature, ambient humidity, barometric pressure and a set of weights are again available.
The gauge pressure generated by the state standard is calculated according to the definition equation:
Where it stands for:
p .......….... | pressure, |
λ ...........…. | deformation coefficient of the piston-cylinder, |
α .......…..... | the angle between the direction of acceleration due to gravity and the perpendicular to the piston area, |
m .....…...... | mass, |
g ......…...... | acceleration due to gravity, |
αp......…...... | coefficient of thermal expansion of the piston, |
αc ......…..... | coefficient of thermal expansion of the cylinder, |
Γ …….…... | surface tension of the oil medium, |
c …….…... | the circumference of the piston at the top edge of the gauge, |
ρa......…...... | air density, |
ρm......…...... | density of weights, |
T0 .......…..... | reference temperature, |
Aef(0,T0)...... | the size of the effective area of the piston-cylinder at zero pressure and reference temperature. |
The standard successfully participated in two key comparisons under KCDB.