Dual range pistons for pressure calibration

Dual piston deadweight testers can greatly enhance a lab?s ability to calibrate wide pressure ranges with the best accuracy. With transducers and devices under test (DUTs) which have a wide measuring range, calibration can be a lengthy process, as you need to change pistons in between test points so as to calibrate its entire range.
However, a dual piston deadweight tester is equipped with a higher range piston and low range piston, which allows the technician more flexibility and efficiency when it comes to calibration. This advancement originates from decades of innovation and customer interaction to find a solution for industry needs.
Formula for pressure calculations
Since the Industrial Revolution, high accuracy pressure measurement has been a key requirement in process industries. Pressure measuring instruments like gauges were employed to measure and monitor pressure conditons. They need to be calibrated against instruments of a higher amount of accuracy. Deadweight testers (generally known as pressure balances) are high accuracy instruments found in the calibration of electronic or mechanical pressure instruments. The core element of a deadweight tester is a precisely manufactured piston-cylinder system, onto which a mass load is applied to be able to generate the individual test points in a calibration.
The mass load is proportional to the target pressure, which is achieved through optimally graduated masses. The look of the complete calibration system, in addition to the precise manufacturing of the piston and cylinder, ensure quality performance with long free-rotation time and low sink rates of the piston. With measurement uncertainties down to 0.002% of reading, deadweight testers will be the golden standard in calibration.
Moneyback includes a single piston-cylinder system. This involves mass sets to be changed in order to calibrate multiple or wide measuring ranges. This may become a cumbersome process, one that requires many resources. In 1953, the entity today referred to as DH-Budenberg pioneered the first dual range piston-cylinder technology with two pistons housed concentrically in a single unit. DH-Budenberg was later acquired by WIKA in 2011. The first design included 1/8 in2 (low pressure) and 1/180 in2 (high pressure) pistons housed in one unit. Utilizing a single mass-set it was now possible to generate two points of equilibrium at 55 bar (low pressure) and 550 bar (ruthless) respectively. This is followed with the release of high pressure variant which could generate pressure upto 1100 bar.
Explanation dual piston design
The initial dual piston design was largely constructed of tool roll, and had an accuracy of 0.03 % of the pressure being measured in the typical model and 0.05 % in the ruthless model. In dual piston calibration, the load on the low pressure piston is used in the auxiliary piston, which is directly connected to the weight carrier. When correct pressure is obtained, the piston head skirt floats within the reduced range or ?blue band.? To reach ruthless, the pressure is increased and the low pressure piston rises until a knife-edge on the bottom flange makes a seal contrary to the low pressure cylinder and acts because the high pressure cylinder. Because Off-kilter does not contribute to the overall weight of the piston and weight carrier, the weight carrier picks up the auxiliary weight to compensate. When correct pressure is achieved, the piston head skirt floats within the high range or ?red band.?
This iconic, patented DH-Budenberg red and blue band piston-cylinder system was re-engineered later with both piston and cylinder components made of tungsten carbide. With the refinements in pressure generation and piston manufacturing processes, dual ranges are actually available around 1,400 bar with accuracies down to 0.006 % of reading.
These developments in dual piston technology made deadweight testers, such as DH-Budenberg?s CPB5800 Hydraulic Pressure Balance, the premier deadweight tester for industrial applications. It is especially ideal for calibrating a transducer with a broad measuring range, while maintaining the high accuracy for testing and calibration. By using just a single mass set and calibrating instrument, this system can automatically switch between multiple test points of high and low pressure, making pressure calibration seamless, efficient and economical.
Note
Further information on our pressure balances are available on the WIKA website.

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