Subject:
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Re: Ranging techniques
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Tue, 1 Jun 1999 10:10:01 GMT
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Original-From:
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Mike Jones <michaelj@wt.SPAMLESSnet>
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Reply-To:
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michaelj@wt.net#nomorespam#
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Viewed:
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811 times
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> The problem is, the output of the sensor is not linear
> and I want to convert the output into inches or feet so it can be used
> along with the sonar output (I plan to implement some sort of comparison
> between sensor readings and have what seems to be the most accurate sensor
> for a given range used). I have logged the average of three readings for
> each inch of range over 18 inches and have found the sensor readings have
> larger changes at short ranges than for the same change in acual distance
> at longer distances. I graphed the readings in excel and it is a nice,
> smooth and predictable curve. I can't find my high school algebra books
> anywhere but I just know there is a method of converting the non-linear
> output to linear inches. (By the way, I modified the output of the sensor
> by subtracting it from 238, which is what appears to be the closest range
> reading obtainable before the sensor becomes unreliable - this gives me an
> output that ranges from zero at close range and about 155 at long range).
> Has anyone had any success at converting the output of this sensor to
> inches or some other linear unit of measure? It would be very helpful if
> somebody assisted my mathematically challenged self.
Why not just use a table of the 18 averaged values for lookup and then estimate
in between the inch measurements. This would be faster than trying to to any
floating point math as long as you don't need too precise of a value (I would
think that 1/2 or 1/4 inch should be as accurate as you would need).
Mike
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Message has 1 Reply:
 | | Re: Ranging techniques
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| (...) Yes, this is the method we used along after hacking up a cubic approximation using Graphical Analysis. The lookup table is plenty accurate and also demonstrates that some problems are best solved using nothing more than a ruler and a few spare (...) (25 years ago, 4-Jun-99, to lugnet.robotics.handyboard)
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