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I'm working with the DYP-ME007Y ultrasonic sensor for a project and I bought two off eBay. Both seem to work however they have this 'unknown' twistable part which is in a different position of rotation on both. I have a suspicion it is a trim pot of some description, but I would like to make sure. It could possibly be a method of tuning.

The part in question is the tall silver component with the black circle on top. The only writing on it is 7708, on the other side. Part

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Ignacio is corrent on what it is, also see the answer to another question on what it does: electronics.stackexchange.com/questions/56/… - you might be able to tune it a bit to get a higher output level. – PeterJ Jun 7 '14 at 2:08
Thanks for that extra bit of information Peter, any idea how I could measure any changes it causes? The distance output hasn't changed so far when I altered it and as I'm unfamiliar with inductors in this sort of circuit I wouldn't know what else to measure – jonathongrigg Jun 7 '14 at 23:53
I was thinking it might improve the range a little, but if you haven't found it to increase it maybe it's not worth worrying about. Note that it shouldn't change the measurement - I was thinking maybe it would make it work over 11 meters instead of 10 for example. Those inductors are very cheap so they might have just used it for that reason rather than it being adjustable and in practice it might not make much difference. – PeterJ Jun 8 '14 at 0:01
My trial was against a flat wall ~1.8m away which is within the advertised 3m range. I might try in an open scenario and see whether it does increase the maximum reading. It wouldn't surprise me though as you said if they were just used for cost reasons, it might also have allowed for manufacturing tolerances. – jonathongrigg Jun 8 '14 at 0:13
up vote 6 down vote accepted

Looks like a variable inductor to me. The black circle is the top of a ferrite core that changes position within the coil.

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This is variable transformer. Primary winding goes from frequency generator, secondary winding forms resonance circuit with piezo element (ultrasound transducer).

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