10m-10cm distance measurement with 1cm accuracy at a rate of 50Hz

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Do you know any small size, light weight distance sensor with the following
specs;
    * Range : 10cm to 1000cm (10meter )
    * Rate    : 50 Hz (50 measurements/sec)
    * Accuracy : 1cm
    * Must operate on any surface (except transparent surfaces like glass)
    * Power requirement : Less than 5W
    * Weight : Lighter than 500grams
    * Vibrartion sensitivity : Must operate 0-500Hz



Re: 10m-10cm distance measurement with 1cm accuracy at a rate of 50Hz


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No, but I guess they excist. You could use RADAR, simply send out sound,
and see how long time it takes for it to return (knowing sound travels
more or less 300m/s. This would make it dependent on the altitude, but
it'd be easier to make with a microcontroller than light/radio based
RADAR, since light would require really really good timing...


--
MVH,
Vidar

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Re: 10m-10cm distance measurement with 1cm accuracy at a rate of50Hz


What about the samll commercial distance measuring units they sell at builders
shops?  Cheap and easy to get,  But I dont know about the specs

David


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Re: 10m-10cm distance measurement with 1cm accuracy at a rate of 50Hz



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   Use of light or radio pulses (as in RADAR) is just as easy as use of
sound pulses; timing is easy.
   Been around since the 1940's.

Re: 10m-10cm distance measurement with 1cm accuracy at a rate of 50Hz



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Ranging radar is very much more difficult than dopler radar. Dopler radar is
fairly easy to do, $100 bucks or so -- hell you can buy dopler radar off
the net to measure your pitching speed.

Ranging radar has to emit a pulse and measure the time delay from transmit
and recieve. With SONAR, this is dist = (340/2)/T (we divide by two because
echo is a two way trip), well in the millisecond range. With RADAR this is
dist = (300000000/2)/T. If you are measuing meters you are in the nano
second range. If you are trying to measure centimeters you are in the pico
second range.

This is not to say it can't be done, but it would be very expensive.





Re: 10m-10cm distance measurement with 1cm accuracy at a rate of 50Hz



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Where ? Any source please?



Re: 10m-10cm distance measurement with 1cm accuracy at a rate of 50Hz



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There are ways round this.

If you transmit continuously a signal modulated with a PRBS pattern, then
the receiver can find the range at any instant by correlation - basically
find the time slip that gives maximum correlation between transmitted and
received patterns. This also works for multiple objects in the FOV. Hardware
wise this would probably be easiest done with a small fpga.

Laser rangefinders have a similar trick. Basically you modulate the
transmitted signal with several different frequencies, and measure the phase
difference between Tx and Rx signal for each one. With a judicious choice of
frequencies, there is only a single range at which a given set of phase
values can occur.

The Tx and Rx sensors need to be physically separated so that the Rx does
not get overwhelmed.

Yet another approach feeds back the received signal to the transmitter, so
that the whole system oscillates. The frequency of oscillation is directly
related to the round trip delay and hence distance.

Have fun !
Dave




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Re: 10m-10cm distance measurement with 1cm accuracy at a rate of 50Hz



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There are ways round this.

If you transmit continuously a signal modulated with a PRBS pattern, then
the receiver can find the range at any instant by correlation - basically
find the time slip that gives maximum correlation between transmitted and
received patterns. This also works for multiple objects in the FOV. Hardware
wise this would probably be easiest done with a small fpga.

Laser rangefinders have a similar trick. Basically you modulate the
transmitted signal with several different frequencies, and measure the phase
difference between Tx and Rx signal for each one. With a judicious choice of
frequencies, there is only a single range at which a given set of phase
values can occur.

The Tx and Rx sensors need to be physically separated so that the Rx does
not get overwhelmed.

Yet another approach feeds back the received signal to the transmitter, so
that the whole system oscillates. The frequency of oscillation is directly
related to the round trip delay and hence distance.

Have fun !
Dave




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Re: 10m-10cm distance measurement with 1cm accuracy at a rate of 50Hz


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You can't meet the 50Hz requirement at maximum range with sound in air, the
best you could get would be about 16Hz.
(assuming 330 metres/second)

Deep.



Re: 10m-10cm distance measurement with 1cm accuracy at a rate of 50Hz


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No, you can get higher, ...
... why wait until a pulse is received ?
Ok next thing to do is "modulate" the pulses,
for example,
   send a puls
   send a second puls 10 msec later
   next puls 15 msec later
   next puls 12 msec later
By now combining the results of multiple measurements,
you can avoid the ambiguity.

A more diffcult way is to use continuous wave (of course modulated)
ultrasound.

Stef Mientki
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Re: 10m-10cm distance measurement with 1cm accuracy at a rate of 50Hz



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How do you differentiate between pulses? What about echos from multiple
surfaces at different distences?

Re: 10m-10cm distance measurement with 1cm accuracy at a rate of 50Hz


<Yugo> wrote:

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Interesting criteria

Speed of sound is about 340 meters per second, if you want a range of 10
meters, that is a round trip of 20 meters. 340 meters per second / 20
meters round trip, that means a theoretical maximum of about 17 readings
per second, and a practical max of about 10.

Unless you can alter your specifications, SONAR is out of the question and
you'll have to use rangning RADAR.

Ranging RADAR is expensive because, unlike police speed traps which use
dopler frequency shift on the bounced return signal, a ranging radar
system, like a ranging sonar system, needs to measure between send and
recieve. Where sound travels at a pokey 240 meters per second and can be
easily measered, light travels a little less than 300,000,000 meters per
second, and requires some real precision to measure. Especially at the cm
to 10 meter range.



Re: 10m-10cm distance measurement with 1cm accuracy at a rate of 50Hz



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Indeed.


Unless, he alters the frequency for each reading. Using different
frequencies, and only listening for the right frequency, you might make
it work... but then again, Ranging RADAR is better.


--
MVH,
Vidar

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Re: 10m-10cm distance measurement with 1cm accuracy at a rate of 50Hz


CHIRP
MEASURE RX BEAT FREQ = DISTANCE
SAMPLE AT 50CPS
: mlw wrote:
:
: >
: > Interesting criteria
:
: Indeed.
:
: > Speed of sound is about 340 meters per second, if you want a range
of 10
: > meters, that is a round trip of 20 meters. 340 meters per second /
20
: > meters round trip, that means a theoretical maximum of about 17
readings
: > per second, and a practical max of about 10.
:
: Unless, he alters the frequency for each reading. Using different
: frequencies, and only listening for the right frequency, you might
make
: it work... but then again, Ranging RADAR is better.
:
:
: --
: MVH,
: Vidar
:
: www.bitsex.net


Re: 10m-10cm distance measurement with 1cm accuracy at a rate of 50Hz



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Not necissarily -
www.batforblind.co.nz
(though there is a "retrace" period to deal with)

M

Re: 10m-10cm distance measurement with 1cm accuracy at a rate of 50Hz



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   So?
   Radio waves travel about 11 inches per nanosecond (30cm); which is a
long time.
   So 10cm is about 0.3nSec (one way) which means some special care must
be taken or subterfuge - like variable CW: make the time of flight a
part of an oscillator and then measure the frequency.
   Makes the job a lot easier, methinks.
   1cm accuracy translates to 2cm round trip variance or 60pSec if one
thinks of pulses.
   Lessee...say 2000cm max round trip is 66.67nSec time for 14.999MHz;
1998cm round trip is 66.60nSec time for 15.015MHz.
   Seems to be easily resolvable.
   Just build an amplifier and it will oscillate...

Re: 10m-10cm distance measurement with 1cm accuracy at a rate of 50Hz


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Check into the SICK laser rangers. Not cheap, though.

--
(Replies: cleanse my address of the Mark of the Beast!)

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Re: 10m-10cm distance measurement with 1cm accuracy at a rate of 50Hz



<Yugo> wrote in message
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following

Yugo - I don't know if the range or all other constraints are satisfied, but
you may want to have a look at the Sharp ranging modules, IR based IIRC.
Have a look on the Manuco website.
rob
http://www.manuco.com.au /



Re: 10m-10cm distance measurement with 1cm accuracy at a rate of 50Hz


Leica has a few hand-held laser distance devices that seem close to
your specs.
http://www.leica-geosystems.com/cpd/en/products/laser_distancemeter

Below is some data about their higher end system.  But they also have a
cheaper version that has the similar measurement abilities.
3D%3D3D%3D3D%3D3D%3D3D%3D3D%
The Leica DISTO99% plus is the only device in the world that offers the
highest accuracy, attractive design and wireless data transfer by means
of BLUETOOTHAE% in one package. Even if you are currently still working
with paper and pencil, integrated BLUETOOTHAE%  technology allows you to
make the change at any time and to record your values electronically.
The data can be transferred on site wireless to a PDA (Pocket PC) or
directly to a laptop and easily used for other purposes.

 Range of measurement: 0.2 up to 200 m
 (0.7 up to 650ft). Accuracy:  B1%1.5mm
 (0.06in)
3D%3D3D%3D3D%3D3D%3D3D%3D3D%

Regarding price; I looked at a similar system by another vendor a few
years back and it was around $800 at the time.


Joe Dunfee


Re: 10m-10cm distance measurement with 1cm accuracy at a rate of 50Hz


===========
The Leica DISTOT plus is the only device in the world that offers the
highest accuracy, attractive design and wireless data transfer by means
of BLUETOOTH® in one package. Even if you are currently still working
with paper and pencil, integrated BLUETOOTH®  technology allows you to
make the change at any time and to record your values electronically.
The data can be transferred on site wireless to a PDA (Pocket PC) or
directly to a laptop and easily used for other purposes.

 Range of measurement: 0.2 up to 200 m
 (0.7 up to 650ft). Accuracy:  ±1.5mm
 (0.06in)
===========


What is the theory behind laser ranging?

Thanks.



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