Liquid is the special sensing unit in the connected pipe measurement system.The lag of its dynamic characteristic research restricts the system to be used in the dynamic measurement.A U pipe with equal diameter is used as the model

system transfer function is deduced and four important performance indexes in time domain are gotten

such as rise time

peak time

maximum overshoot and governing time

etc.They affect dynamic performances of the liquid.From analysis the diameter of pipe

total length and movement viscosity coefficient of liquid are key elements which influence dynamic characteristics of liquid.Dynamic characteristics experiment is finished on this foundation.The results show that experiment values are consistent with theoretical ones.It is feasible to use a connected pipe measurement system in low-frequency dynamic measurement.