Underwater piezoelectric sensor array receive sensitivity

[nauman]

Hi all

I have some confusion about piezoelectrical sensors combination. If i have three acoustic piezoelectrical sensors (with same receive sensitivity in dB ref V/1uPa) placed at specific distance, these sensors receive acoustic signal from a sound source placed at far field distance (Plane Wave) and from broadside. I receive output of these sensors through individual preamplifiers, add them through hardware like summer circuit adder or in software after digitization and in this way got an 'Array Gain' due to addition of phase aligned sinusoidal signals. This array gain ultimately adds in receive sensitivity of individual sensor since signal is coming from broadside and an overall inrease in receive sensitivity of combine 'array of 03 sensors' occurs. Till now, things are straight forward.

Now my question is that if i hardwired + polarity terminalof all three piezo sensors together and -polarity terminals together, and connect them to a single preamplifier, will i get the same increase in receive sensitivity due to 'Array Gain' as in above case?

Thanks

 

[Baluncore]

... will i get the same increase in receive sensitivity due to 'Array Gain' as in above case?

No, you will not. The array pattern may be the same, but the magnitude of the main-lobe energy will be less.

A transducer is impedance matched to its preamplifier, to maximise power transfer and prevent retransmission.

If you wire three transducers in parallel, you will not be matching their impedance, and you will be retransmitting some of the transducer signal energy.

 

[nauman]

A transducer is impedance matched to its preamplifier, to maximise power transfer and prevent retransmission.

But i am talking about transducers in reception mode only in which i think these act as a voltage sources not power source!

 

[Baluncore]

But i am talking about transducers in reception mode only in which i think these act as a voltage sources not power source!

I believe the transducer is a bidirectional or reciprocal device that can work as a transmitter or a receiver. It is connected to the electronics with a transmission line. Voltage implies current, which implies power, which is the rate of energy transfer.

If the transmission line has a characteristic impedance of; Zo,
and there is a voltage; v, present on the matched impedance line,
then a current of; i = v / Zo will be flowing.
The power will then be; W = v * i .

If the transducers include a preamplifier, then the problem becomes one of connecting four transmission lines with a four way coupler, without introducing an impedance mismatch. The efficient way to do that is with a three input summing amplifier, driving one output line.