Dual piston deadweight testers can greatly enhance a lab?s capability to calibrate wide pressure ranges with the highest accuracy. With transducers and devices under test (DUTs) that have a wide measuring range, calibration can be quite a lengthy process, as you must change pistons among test points in order to calibrate its entire range.
However, a dual piston deadweight tester has a higher range piston and low range piston, that 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
Because the Industrial Revolution, high accuracy pressure measurement is a key requirement in process industries. Comfortable 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 used in the calibration of electronic or mechanical pressure instruments. The core component of a deadweight tester is a precisely manufactured piston-cylinder system, onto which a mass load is applied so that you can generate the average person test points in a calibration.
The mass load is proportional to the prospective 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 will be the golden standard in calibration.
Behind The Scenes includes a single piston-cylinder system. This requires mass sets to be changed to be able to calibrate multiple or wide measuring ranges. This could 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 initial design included 1/8 in2 (low pressure) and 1/180 in2 (ruthless) pistons housed in a single unit. Using a single mass-set it had been now possible to generate two points of equilibrium at 55 bar (low pressure) and 550 bar (high pressure) respectively. This is followed with the release of ruthless variant which could generate pressure upto 1100 bar.
Explanation dual piston design
The first 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 strain on the reduced pressure piston is used in the auxiliary piston, which 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 attain ruthless, 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 because the high pressure cylinder. Since the low pressure piston will not contribute to the entire 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 manufactured from 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 can be found on the WIKA website.