Fluke 2470 specifications Explanation of Pressure Calculation Worksheet, Introduction

Appendix A

Explanation of "Pressure Calculation Worksheet"

Introduction

See Tables at the end of this appendix.

These tables may be used with gas and hydraulic piston pressure gauges that are operated with an atmospheric reference or vacuum reference. PA represents the pressure at the piston reference

gauge level, PB represents the pressure desired at the device under test, and PH is the head

pressure created by the pressure medium and the difference in height between the piston pressure gauge and the device under test.

A.A minimum of six significant figures must be used in all calculations involving reported constants, masses, etc. The manufacturer's claims for accuracy assume the local gravity to be known to at least six significant figures

B.When the piston pressure gauge is used as a standard of pressure, it is convenient to perform the pressure-to-mass calculations in advance of operating the standard. Since the piston gauge temperature fluctuates while it is operated, a confusing point in the procedure is the necessity for the temperature of the gauge to be predicted prior to operation. This “expected temperature” however is used to allow the pressure calculations to be performed. Once the piston pressure gauge is floating at the intended pressure, a final temperature observation is made and then “trim” masses are loaded onto the piston gauge to correct for any temperature variations that exist between the expected and the actual temperatures. The final column in the worksheet is used to calculate the temperature coefficient, which defines the amount of trim that is required to correct for this temperature change.

It is usually prudent to select an expected temperature ( t ), which is lower than any temperature that will be experienced. This is so that the operator can always add mass to correct for the actual temperature. Adding mass is generally more convenient than subtracting mass from the planned loading arrangement. Standard metric trim mass set is entirely suitable for this purpose.

A-1