Fluke 2470 User Manual

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Measurement of pressure with the piston pressure gauge is subject to uncertainties 

resulting from effects other than those of elastic distortion. But, it was appropriate that 

the subject of elastic distortion be discussed first, since this characteristic is largely 

responsible for the various designs that have been developed. 
Measurement processes proposed for high accuracy are disturbed by limitations in the 

performance of the equipment, by small changes in the environment, and by operational 

procedures. The disturbances can be reduced to a degree by exercising control of the 

apparatus. Some of the disturbances are difficult to control; it is easier to observe their 

magnitudes and apply corrections for their effects. 
The factors that affect a pressure measurement process when conducted with a piston 

pressure gauge are described below. It is important that the operator is acquainted with 

these factors and become accustomed to recognizing their presence. The success of the 

measurement will depend upon the degree to which control has been maintained, or to the 

completeness by which corrections were applied for these factors. 

•

  Elastic distortions of the piston and cylinder. 

•

  Effects of gravity on the masses. 

•

  Temperature of the piston and cylinder. 

•

  Buoyant effect of the atmosphere upon the masses. 

•

  Hydraulic and gaseous pressure gradients within the apparatus. 

For a consolidation of these various corrections, see Appendix A of this manual.  

Appendix A contains a Pressure Calculation Worksheet (both SI and English units) with 

instructions. The Pressure Calculation Worksheet will step the user through the necessary 

corrections as applied to calibrations with a piston pressure gauge. 

Pressure results from the application of a force onto an area. Numerically, it is the 

quotient of the force divided by the area onto which it is applied:  

=

 

Where:  

 

Represents the pressure 

 

Represents the force 

 

Represents the area