Dual piston deadweight testers can greatly enhance a lab?s ability to calibrate wide pressure ranges with the highest accuracy. With Desperate and devices under test (DUTs) that have a broad measuring range, calibration can be quite a lengthy process, as you must change pistons in between test points so that you can 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 in terms of calibration. This advancement comes from decades of innovation and customer interaction to find a solution for industry needs.
Formula for pressure calculations
Because the Industrial Revolution, high accuracy pressure measurement is 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 an increased degree of accuracy. Deadweight testers (generally known as pressure balances) are high accuracy instruments used in the calibration of electronic or mechanical pressure instruments. The core component of a deadweight tester is really a precisely manufactured piston-cylinder system, onto which a mass load is applied in order to generate the individual test points in a calibration.
The mass load is proportional to the mark pressure, that is achieved through optimally graduated masses. The design of the complete calibration system, along with 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 right down to 0.002% of reading, deadweight testers are the golden standard in calibration.
A deadweight tester typically includes a single piston-cylinder system. This involves mass sets to be changed so that you can calibrate multiple or wide measuring ranges. This could become a cumbersome process, one which requires many resources. In 1953, the entity today referred to as DH-Budenberg pioneered the initial dual range piston-cylinder technology with two pistons housed concentrically in one 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 a single unit. Using 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 was 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 made of tool roll, and had an accuracy of 0.03 % of the pressure being measured in the typical model and 0.05 % in the high pressure model. In dual piston calibration, the load on the low pressure piston is transferred to the auxiliary piston, that is directly linked to the weight carrier. When correct pressure is obtained, the piston head skirt floats within the low range or ?blue band.? To reach high pressure, the pressure is increased and the reduced pressure piston rises until a knife-edge on underneath flange makes a seal against the low pressure cylinder and acts as the high pressure cylinder. Since Download will 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 up to 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 really is especially useful for calibrating a transducer with a broad measuring range, while maintaining the high accuracy for testing and calibration. With the use of only a single mass set and calibrating instrument, this technique 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 can be found on the WIKA website.