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Topic Title: Ultrasonic Sensor - Voltage Output
Topic Summary: Voltage output calculation.
Created On: 28 January 2011 12:22 PM
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 28 January 2011 12:22 PM
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Posts: 1
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.

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