Introduction
The Pressurements 3000 Series is
the culmination of over 50 years experience
in the production and design
of primary pressure standards. With
features designed to improve accuracy
and performance, increase reliability
and simplify operation these deadweight
testers can be used to calibrate
virtually any pressure sensing device,
including transducers, transmitters,
gauges or pressure switches.
Each instrument is supplied with a
detachable lid that makes it neat, compact
and easily portable. The weight
masses are stored in a high-quality
case with a self-locking mechanism to
protect them during transit.
All units are provided with a traceable
certificate of accuracy, weight
mass details, 1/8 inch, 1/4 inch,
3/8 inch and 1/2 inch NPT or BSP
female adaptors, operating fluid (where
applicable) and spare seals.
The piston/cylinder assemblies
are manufactured to the very highest
standards with certified accuracies
trace-able to international standards
laboratories such as the National
Institute of Standards and Technology
(NIST).
Operating principle
Deadweight testers are the primary standard
for pressure measurements. Utilizing the well
proven piston-gauge system consisting of a
vertically mounted, precision lapped piston and
cylinder assembly, accurately calibrated weight
masses (Force) are loaded on the piston (Area),
which rises freely within its cylinder. These
weights balance the upward force created by
the pressure within the system.
The pressure is measured when placed on
a correctly spinning and floating piston. The
total pressure measured is the summation of the
weights plus the piston weight carrier assembly.
Instrument base
There are four basic variations in the pneumatic
offering; single pressure, single vacuum, dual
vacuum and pressure, and oil-lubricated pneumatically
driven high-pressure models. Pressure
or vacuum is generated by an external source or
an optional built-in hand pump. The hand pump
option is not available on instruments above
500 psi (35 bar).
Piston/cylinder assemblies
The piston/cylinder assembly is the heart of
each deadweight tester. They are manufactured
from materials that provide stability, durability,
and low thermal coefficients and distortion. Our
experience and knowledge of piston/cylinder
production and calibration ensure the precision
and performance required for today’s demanding
calibration requirements.
Weight masses
Standard weight masses are series 3 nonmagnetic
austenitic stainless steel. Each mass
is marked with the serial number of the instrument
and the nominal pressure value relative to
the high- or low-pressure piston, when applicable.
Vacuum weights and the optional fractional
weights are stainless steel and/or solution heat
treated aluminum.
Gravity correction
Gravity varies significantly with geographical
location and this variation has a direct effect
on the force of the weights and the accuracy
of the deadweight tester. Each instrument can
be calibrated to local gravity at no extra cost. If
unspecified, instruments will be calibrated to
Standard Gravity at 980.665 cm/s2.
Gas supply
All instruments are fitted with a / NPT female
external supply port for connection to the gas
supply source. A compressed gas bottle (nitrogen
or dry air) fitted with a pressure regulator is
recommended. Ten percent above the maximum
pressure is required. A built-in hand pump is
available on some models to generate pressures
to 300 psi (20 bar).
For vacuum requirements, an external
vacuum pump can be connected to the / NPT
port. The built-in hand pump will also generate
up to 90 % vacuum.
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