Close Range Ultrasonic Sensors Needed
I have an application that requires a close range single transducer head ( unlike the PING which has a separate emitter and receiver transducer head) ultrasonic sensor.
The distance from the senor to the target may vary from approx 1" ( 20mm ) to 6" ( 150mm ) and the sensor needs to enable distance determinations in approx 1mm steps or better.
The closest sensor that I found is the Daventech SRF01 ( http://www.robot-electronics.co.uk/htm/srf01tech.htm ) which can measure distances to targets as close as 0" (that's right "zero" inches); HOWEVER, the SRF01 enables distance measurements only in Centimeters and not Millimeters, which isn't accurate.
Suggestions are greatly appreciated!
The distance from the senor to the target may vary from approx 1" ( 20mm ) to 6" ( 150mm ) and the sensor needs to enable distance determinations in approx 1mm steps or better.
The closest sensor that I found is the Daventech SRF01 ( http://www.robot-electronics.co.uk/htm/srf01tech.htm ) which can measure distances to targets as close as 0" (that's right "zero" inches); HOWEVER, the SRF01 enables distance measurements only in Centimeters and not Millimeters, which isn't accurate.
Suggestions are greatly appreciated!
Comments
Thanks
-Phil
Thanks for your reply.
As the target medium may be reflective as well as of varying light absorbency, optical would be problematic.
-Phil
In principle, a simple closed loop audio feedback circuit could be used to determine distance if you could place the receiver on the target or arrange the transmitter and receiver in such a way that the sound bounces off of the target to the receiver.
As an example: think of when the speaker (<-person) at the microphone gets to close to the loud speaker and you hear the shrill audio feedback. If you were to measure that shrill frequency, you would find that it is directly proportional to the distance between the microphone and the speaker.
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Beau Schwabe
IC Layout Engineer
Parallax, Inc.
The target medium would be different type of products including food products such as meat cuts and fish fillets.
Thank you for your reply.
The optimum configuration would be for the ultrasonic receiver to be placed away (ie., non-contact) from the target medium. However, if I understand your post correctly, is it the case that whether the ultrasonic receiver is physically placed on the target medium OR not, that the effective distance gauging ability of the sensor can be improved by use of a closed loop audio feedback circuit?
In advance, thank you.
"if I understand your post correctly, is it the case that whether the ultrasonic receiver is physically placed on the target medium OR not, that the effective distance gauging ability of the sensor can be improved by use of a closed loop audio feedback circuit?"
This would no longer be in the realm of ultrasonic but instead audio that you could hear. ...But you could pulse it (enable it) so that the high frequency squeal would be perceived as a few 'clicks' to a nearby observer rather than a constant irritating squeal.
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Beau Schwabe
IC Layout Engineer
Parallax, Inc.
In another thread (scroll down the page), I showed how to measure distance using a laser line generator and a TSL1401 linescan sensor. Perhaps something like this could work for your app.
Beau's idea sounds promising as well, so long as the mechanical noise from the conveyor doesn't cause interference.
-Phil
I really appreciate your thoughts on this. Have a great day!
It might be theoretically possible with some kind of piezo transducer working above 200 KHz but I'm not aware of any standard product that works like that.