Joined: 28 January 2011
I need some help.
I am trying to design a circuit to detect ultrasounds.
I want to use the Knowles's sensor SPM0404UD5.
To know the voltage output from the sensor, I use the following data:
dB = 20log(M/1) (reference 0dB = 1V/Pa @ 1kHz);
The typical sensor's sensitivity @ 1kHz is -42;
The maximal sensitivity, in relation to 1kHz, is 12.5dB (35kHz to 55kHz region), but to do the calculation I used 15dB instead of 12.5dB.
With these data, I calculated the voltage output of the sensor:
M = 10^(dB/20) <=> M = 10^((-42+15)/20)=44.668mV/Pa
1psi = 6895Pa
So, If there is, for example, a pressure of 100psi the voltage output is:
V = 44.668*10^(-3)*100*6895 = 30799V.
Am I correct?
If not, what is the correct approach?
I have no sure about these calculation because the final result gives me a very high output voltage.
Thank you for help.