Fluke 2470 specifications Reference Plane Determination

RUSKA 2470

Users Manual

It is common practice to associate this position directly with the piston as the datum to which all measurements made with the piston are referenced. It is called the reference plane of measurement, and its location is determined from the dimensions of the piston. If the submerged portion of the piston is of uniform cross section, the reference plane is found to lie conveniently at the lower extremity as shown in 2-4. If, however, the portion of the piston submerged is not uniform, the reference plane is chosen at a point where the piston, with its volume unchanged, would terminate if its diameter were uniform.

The reference plane of the standard is the effective bottom of the measurement piston. This location can be correlated to the index on the mass stack using the L1 dimension (found on Calibration Report for the Piston/Cylinder) and the D Dimension (found on Calibration Report for the Mass set).

glg02.bmp

Figure 2-4. Reference Plane Determination

When a pressure for the piston pressure gauge is calculated, the value obtained is valid at the reference plane. The pressure at any other plane in the system may be obtained by multiplying the distance of the other plane from the reference plane by the pressure gradient and adding (or subtracting) this value to that observed at the piston reference plane.

2-6