For pressures
below 1333Pa, we use the transfer Standards described on the [Vacuum]
page which, with their 15 year history of NPL re-calibrations, once again
provide the lowest UKAS accredited uncertainties available.
These transfer standards are regularly cross-compared at 1x10-1 Pa with
a Spinning Rotor Gauge and at 1333Pa with either a 60inch or 110inch
Schwien manometer, producing a vacuum calibration facility with outstandingly
low uncertainties.
A gas friction manometer (Spinning Rotor Gauge) is used for high vacuum
calibrations over the range 1x10-4 Pa to 1x10-1 Pa. Traceability is bought-in
from a German DKD accredited vacuum laboratory providing traceability
to the German National Standards at PTB, Berlin.
Chell are, we believe, the only calibration laboratory in the World
to have two accredited Schwien Merco-Master manometers working side-by-side.
This facility affords us the ability to either measure or generate both
absolute and differential pressures over the range of 1.7 kPa to 379
kPa in two discrete channels simultaneously, with uncertainties better
than 30ppm.
Best measurement capability pressures above the range of the Schwien
manometers are generated using a gas pressure balance calibrated for
mass and effective area by laboratories in USA, France and Germany, all
having direct traceability to their National Standards. The DHI 7601
pressure balance is a “State-of-the-Art” device that is also
used to 'cross-float' both Schwien manometers as an additional periodic
confidence check.
Chell is the best-placed calibration laboratory in the World for the
calibration of safety-critical aerospace test sets such as Air Data Test
Sets and Pitot Static Testers, having both a 110in and a 60in Schwien
manometer working as a pair. In this way Ps and Pt channels may be both
exercised and calibrated independently and simultaneously in exactly
the same way as they are used in service. This provides invaluable feedback
to the equipment operators as to the efficacy of the use of a particular
device in any application.
Sensor manufacturers are now able to have their safety-critical sensors
evaluated for aberrations such as Creep and Drift using the only standards
having the sensitivity and repeatability to see the effects. This type
of performance evaluation is impossible using any other type of standard,
making Chell unique in Worldwide accredited laboratories.
In addition to standard pressure transducers the following generic types
of pressure instruments are also supported:
- Resonant and quartz bourdon type transducers*
- Vibrating element transducers*
- Precision pressure generators & transfer standards
- Air Data Test Sets
- Pitot Static Test Sets
- Pressure Scanners, both high & medium density*
- High accuracy capacitance manometers
- Precision aneroid barometers
- Standard test gauges
- Digital pressure indicators, calibrators & controllers
* High accuracy transducers with temperature and pressure outputs can
be calibrated over a series of temperatures. Polynomial coefficients
are then supplied to the customer for use in linear regression calculations
to optimise transducer performance.
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