An initial investigation of the damped resonant behaviour of gas-operated pressure balances

The aim of this investigation into the damped resonant behaviour of the piston of gas-operated pressure balances is to provide insights into ways of improving the short-term performance of gas-operated pressure balances. Initial measurement results are reported for the damped resonant behaviour of two different pressure balances as a function of system volume. The pressure balances are operated using air in absolute mode at 100 kPa and the system volume is varied from about 10 mL to 250 mL. Values for the period, the logarithmic decrement λ and the Q of the oscillation are obtained by fitting the measured damped oscillatory motion of the piston height to a classical damped oscillator model. Results show that the damping is dominated by non-adiabatic pressure variations in the system volume and not by viscous damping of the vertical motion of the piston in the cylinder. The settling time for the oscillations to damp out is primarily determined by the period of oscillation with a lesser influence from variations in λ. Implications for improving pressure balance performance are discussed.