of unity, or
In other words, the measured pressure
the actual pressure. Thus, higher resonant frequencies
and greater damping factors (up to critical damping) offer better dynamic
The step response or pop-test has its advantages
system response. This “pop test” or step response
method is shown in Fig.
One can apply either a positive step (step
increment in pressure) or a negative step (step decrement in pressure).
An ideal blood pressure measurement system follows the step exactly,
with no overshoot or undershoot, and no time delay.
however, overshoot and oscillations are common. Fig.
illustrates the underdamped response
a fluid-filled catheter-manometer
system. The dynamic frequency response in terms of relative amplitude
frequency for the step response
is shown in Fig.
The single resonance peak occurs as the underdamped catheter-
manometer system was approximated by the second order system.
The pop-test (step response) for the dynamic testing of transducer system
resonant frequency. The catheter transducer system is seen to be
In general, linearity, hysteresis, and dynamic system response are
necessary considerations in fluid-filled blood pressure measurement
Linearity refers to the output response vs. input applied