Full Range Of Deadweight Testers Added To CLG WebsiteThings to consider when selecting a deadweight tester
Deadweight testers use a precision piston-gauge system consisting of a vertically mounted, piston and cylinder assembly, and accurately calibrated weight masses that are loaded onto the piston.
The first thing to consider is the pressure range. One of the advantages of a DWT is the wide range of instruments that it can cover. The DWT is an inherent percent-of-reading device, meaning that its performance actually improves as it is used at pressures below full scale. There is a lower breakpoint, normally 10 % of full scale, where the specification ceases to be percent of reading.
When selecting the range of a deadweight tester, first consider the highest pressure that needs to be generated. The full scale needs to be greater than this. Since the accuracy is a percent of reading specification, it is okay to consider possible future expansion and select a DWT that has a higher full scale than what is currently needed.
The next thing to consider when selecting a DWT is the medium to be used. Often the choice of the medium is dependent upon the pressure range required. Pneumatic, or gas, instruments are ideal for lower pressure ranges. Gas is preferred whenever cleanliness is required. In addition, using gas reduces the impact of head height corrections. However, at higher pressures it is necessary to use water or oil.
“ When your work is important, and your measurements matter, an accredited calibration is a great way to provide additional confidence in your measurement results and to demonstrate to your customers that you meet their quality requirements. ”
To establish pressures using a deadweight tester (DWT) or piston gauge, the user must account for the acceleration of gravity at the location where the instrument is operated. It is important to note that the acceleration of gravity varies substantially around the world.
With a range of approximately 0.5 %, the local gravity correction is typically the largest environmental influence acting on the deadweight tester.