A deadweight tester is based on a high accurate manufactured piston and cylinder assembly. This cylinder is mounted in a column. The piston can rotate and move freely up and down. Accurate calibrated masses are loaded on top of the vertical mounted piston. A pressure is applied on the bottom of the piston to lift the piston with masses. This creates a balance between the force made my the masses (downwards) and the force made by the pressure (upwards) and the effective area of the piston cylinder assembly.
Piston cylinder assembly
The piston cylinder assembly is the hart of the deadweight tester and responsible for its high accuracy. The piston cylinders are manufactured with accuracies from 0.015% up to 0.008% of reading. To give an idea of the manufacturing skills the space between the piston and the cylinder is in the μm range and can only be measured in a climatic room.
To guarantee excellent metrological characteristics all pistons and cylinders are made of tungsten carbide. Because of the extreme hardness of this material the pressure distortion (expansion) coefficient is negligible. The low friction coefficient provides minutes of turning just with a little swing.
The masses of the SIKA deadweight tester are made of non magnetic stainless steel. They are marked with a serial number and mass or the equivalent pressure. The weights are tared out to add stainless steel to an internal chamber. This is easy for recalibration or adjustments for gravity compensation.The mass of all weights are listed in the certificate. The weights are protected by a stainless steel carrying case.