With resistive load

Now, when we add the effect of the oscilloscope access, we can simplify the oscilloscope and its probe to a pure resistor, though there is actually a very small capacitance related to the probe and cable (about 30~50pF). If the capacitance of the piezoelectric film is very high, the small capacitance can be ignored.

The voltage measured at both ends of the load resistance RL,

It does not need to be the same as the voltage produced by the "ideal" source.

To see why, it is helpful to redraw the circuit in another way.

Pressure divider

Will redraw the circuit shown in Figure 13 to Figure 14, it is not difficult to see that all the source voltage is not always at the end of the two resistor load.

The capacitor and the resistance are connected in series, and a divider is formed. As the capacitance has impedance and varies with frequency, a part of the total source voltage displayed at both ends of the RL also varies with the frequency.

The VL part of the Vs voltage that appears at both ends of the RL is calculated by the press formula:

In the form:

J said ~1 XC (tick, for capacitor reactance. For the sake of simplification, we ignore the resistance component of the piezo film.

The above formula can be used in simple cases with constant excitation frequency to calculate the voltage level which is expected to be simply calculated, so that the F value can be changed simply. However, in many practical cases, there may be a problem of the distribution of signal energy in the range of frequency band. In this way, it is necessary to take the "frequency response" of the network into consideration.