Establishment of air piston gauge as primary pressure standard at CSIR-National Physical Laboratory INDIA

The air piston gauge (APG) was established at CSIR-National Physical Laboratory, India (NPLI) since 2000. Later the same piston- cylinder(p-c) assembly was calibrated in NIST USA; however, it was never published for metrology communities. As per international protocol, the establishment of the APG as a primary standard, the effective area of p-c assembly, and masses must be directly traceable to SI units. The first time we have calculated the effective area and associated uncertainty of p-c assembly using dimension and mass metrology, traceability to the SI units, i.e., meter and kilogram. To realize the APG as primary pressure standards, we have calculated the effective area of p-c assembly of APG directly from dimension metrology, which is further supported by various other methods. The effective area values obtained in the pressure range of 6.5 – 360 kPa lie in the range of 3.356729 – 3.357248 cm² due to uncertainty limitation in the measurement of dimension of internal diameter of cylinder. The expected values of the effective area which are also measured from cross-float technique against ultrasonic interferometer manometer (UIM), primary pressure standards. The accuracy in effective area measurement is possible only when the resolution in the internal radius of the cylinder should at least be up to 5th decimal order and the uncertainty is 80 nm. The expanded uncertainty was measured nearly 11 ppm at <em>k</em> = 2 by considering the uncertainty in internal radii of cylinder and radii of piston around 80 nm.

Download Full-text

Evaluation of effective area of air piston gauge with limitations in piston-cylinder dimension measurements

Metrologia ◽

10.1088/1681-7575/abe222 ◽

2021 ◽

Author(s):

Vikas Narayan Thakur ◽

Felix Sharipov ◽

Yuanchao Yang ◽

Sandeep Kumar ◽

Jokhan Ram ◽

...

Keyword(s):

Effective Area ◽

Piston Cylinder ◽

Piston Gauge

Download Full-text

Verification of Gas Flow Traceability from 0.1 sccm to 1 sccm Using a Piston Gauge

NCSLI Measure ◽

10.51843/measure.13.3.4 ◽

2021 ◽

Vol 13 (3) ◽

pp. 10-16

Author(s):

Michael Bair

Keyword(s):

Laminar Flow ◽

Gas Flow ◽

Vertical Displacement ◽

Pressure Control ◽

Effective Area ◽

Flow Measurements ◽

Piston Cylinder ◽

Measurement Assurance ◽

Piston Gauge ◽

Means Of Measurement

Fluke Calibration is accredited for gas flow measurements in the range of 0.1 sccm to 6000 slm in nitrogen and air. Traceability is maintained directly through a gravimetric f low standard but only recently from 1 sccm to 10 sccm. The traceability of flow in the range of 0.1 sccm to 1 sccm is based on extrapolation of the use of laminar flow elements (LFE) below 1 sccm. This part of the range has never been completely verified through interlaboratory comparisons, proficiency testing or other means of measurement assurance. In an internal document from DH Instruments in the early 1990s it was suggested that a piston gauge might improve traceability for very low gas flows. In order to prove out traceability in this range an attempt was made to use a piston gauge using a piston-cylinder size of 35 mm diameter as a reference. One reason for choosing a piston gauge as a reference is its pressure control. This is crucial when measuring gas flow through a LFE in this design and range. In addition, the effective area is known to within 0.001 %, leaving the vertical displacement of the piston to dominate the uncertainty of the dimensional part of the flow test. This was a challenge because the measurements required absolute mode and the internal piston position sensor supplied with the piston gauge did not have sufficient precision. This paper describes the theory and design of the gas flow measurement system, the current results, and improvements desired or suggested. Two different designs are discussed, one with a single piston gauge as a reference and one with two piston gauges measuring flow on either side of the laminar flow element. Note: sccm (standard cubic centimeters per minute) is an industry accepted alternative to kg/s [1]. It is used out of convenience to normalize flow rates of gases with significant differences in density.

Download Full-text

The valve maintained tuning fork as a primary standard of frequency

Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character ◽

10.1098/rspa.1934.0003 ◽

1934 ◽

Vol 143 (849) ◽

pp. 285-306 ◽

Cited By ~ 14

Keyword(s):

Radio Frequency ◽

Tuning Fork ◽

Primary Standard ◽

Frequency Standard ◽

National Physical Laboratory ◽

Continuous Operation ◽

Normal Value ◽

Rapid Advance ◽

Satisfactory Performance ◽

Physical Laboratory

In 1922 an investigation was carried out at the National Physical Laboratory to determine the constancy of frequency that could be expected from a valve maintained tuning fork. It was found that the fork was capable of operating with a degree of steadiness of frequency which was greater than was then necessary for most purposes. The investigation resulted in the design of a 1000 cycles per second fork which served as the Laboratory frequency standard until 1931. For precision work it was necessary to measure the frequency of the fork during the observations by comparison with a standard Shortt clock ; but if the accuracy required was less than 2 parts in 10 5 it was sufficient to apply a correction for temperature to the nominal value of the fork frequency. With the rapid advance in radio frequency technique and the ever-increasing number of wireless transmitting stations the problem of frequency standardization became increasingly important; and it was decided to instal a standard, which should be in continuous operation at a frequency within I part in 10 6 of its normal value. As the most suitable frequency for use in conjunction with the existing equipment for the measurement of radio frequencies was 1000 cycles per second, and as the tuning fork had hitherto given a satisfactory performance, it was decided to continue the investigation on the fork to determine whether it could form a frequency standard of the desired degree of accuracy.

Download Full-text

Extending the frequency range of the National Physical Laboratory primary standard laser interferometer for hydrophone calibrations to 80 MHz

IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control ◽

10.1109/58.764860 ◽

1999 ◽

Vol 46 (3) ◽

pp. 737-744 ◽

Cited By ~ 43

Author(s):

T.J. Esward ◽

S.P. Robinson

Keyword(s):

Laser Interferometer ◽

Primary Standard ◽

National Physical Laboratory ◽

Frequency Range ◽

Physical Laboratory ◽

Standard Laser

Download Full-text

Down With Magnification: The Micron Marker Rules!

Microscopy Today ◽

10.1017/s1551929500068164 ◽

1998 ◽

Vol 6 (6) ◽

pp. 12-13

Author(s):

Joe Geller

Keyword(s):

Quality Control ◽

National Physical Laboratory ◽

Image Display ◽

Sem Image ◽

Si Units ◽

Current Wave ◽

Physical Laboratory ◽

The Uk ◽

Almost All ◽

The U.S

With today's current wave of quality consciousness, our quality control people tell us we MUST calibrate our instruments using standards that are traceable to the national laboratories (NIST - National Institute of Standards and Technology in the U.S.,. NPL - National Physical Laboratory in the UK, and others). But, is it really magnification that should be calibrated?While recently walking around the exhibit floor at the Microscopy & Micrcanalysis ‘98 Conference, I noticed the large SEM image display screens that now present our highly magnified specimens. Almost all vividly show a micron (using SI units this should be a “micrometer”) marker as well as the magnification. No doubt the accuracy is within the ± 3% that is commonly quoted by the manufacturers.

Download Full-text

XXIII.The primary standard of mutual inductance of the National Physical Laboratory

The London Edinburgh and Dublin Philosophical Magazine and Journal of Science ◽

10.1080/14786443808562013 ◽

1938 ◽

Vol 25 (167) ◽

pp. 290-317 ◽

Cited By ~ 8

Author(s):

N.F. Astbury

Keyword(s):

Primary Standard ◽

National Physical Laboratory ◽

Mutual Inductance ◽

Physical Laboratory

Download Full-text

Calculation of a primary standard of mutual inductance of the Campbell type and comparison of it with the similar N. P. L. standard

Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character ◽

10.1098/rspa.1922.0047 ◽

1922 ◽

Vol 101 (711) ◽

pp. 315-332 ◽

Cited By ~ 5

Keyword(s):

Primary Standard ◽

Single Layer ◽

Alternating Current ◽

National Physical Laboratory ◽

Mutual Inductance ◽

Secondary Coil ◽

Physical Laboratory

The standard mutual inductance devised and designed by Mr. A. Campbell and constructed in 1907-8 at the National Physical Laboratory has been one of the foundations of our alternating current measurements since that date. It will be sufficient here to note that the special feature in the design of the Campbell type of mutual inductance consists in a primary single-layer winding, so proportioned that the field due to it is practically zero over the region occupied by the secondary coil. By this means the dimensions of the secondary coil are rendered relatively unimportant, so that it may be an overwound many-layer winding, whereby a suitably large value of mutual inductance may be obtained.

Download Full-text