Bias Ultrasonic Receiver?

Hi Guys,

I am still working on my electronic target where I am trying to detect the location (using TDOA) of a bullet on a target. My first revision of the circuit used electret microphones and it seemed to work ok, but not great. After doing some more research, it appears the commercial versions of these targets utilize ultrasonic receivers as simple microphones. I am guessing that the frequency range that they can detect works well for measuring bullet impacts.

The ultrasonic receiver I have bought is a Kobitone 255-400SR10P-ROX with the following specifications:
• Center Frequency: 40.0±1.0KHZ
• Sensitivity: 255-400SR10P-ROX = -65dB (0dB=1 IV/μbar)
• Capacitance: 1800±20%pF @ 1KHZ
• Allowable Input Power: .20 Watt

My question is: Can I substitute the ultrasonic receiver for the electret in this circuit? I don't know much about the theory of "biasing" a microphone and am not sure how to calculate this or the theory behind it.

Does anyone have any comments/suggestions? Thanks!

hi,
Look at this option, you should be able to adapt your circuit to suit the sensor.

http://www.discovercircuits.com/DJ-Circuits/40kultrasoundrvr2.htm

EDIT:
Like this image.

That circuit uses an LM386 audio amp. Perhaps a high frequency op-amp would be a better bet, with a greater slew rate to give better-defined pulse edges for more accurate timing, hence better position measurement.

So are you saying that the ultrasonic receiver does not connect to 5v (biased?) at all?

Thanks

Spine said:

So are you saying that the ultrasonic receiver does not connect to 5v (biased?) at all?

Thanks

Click to expand...

You dont normally bias a ultra sonic sensor...

EDIT:
the image shows why a electro-met needs a bias voltage

There is no "receiver". It is a piezo transducer (microphone). It does not conduct and meaures like a small capacitor.
An electret microphone has a Jfet inside that needs to be biased (powered).