1mm precision 'remote' measurement within 300mm

[Alex_rcpilot]

Hi guys,first of all let me explain 'remote' - it's just like measuring the distance a surface is away from with ultrasonic.No contact reference like rasters or encoders etc.

Ultrasonic sensors have a frequency of 40KHz,thus its cycle is 25us.The time it takes sound to travel 600mm is approximately 1700 us,and 300us for 100mm.It means With a distance of 50mm,you will receive the reflection while you are transmitting the 13th cycle of the original wave.Ultrasonic doesn't seem to be a good way huh?

The surface I am trying to measure is that a luminated spot on human skin is away from a laser generator.Could someone offer a solution?My gratitude in advance.

 

[Someone Electro]

Ultrasonic is ment to be used in wider spased pulses.So you make an short beep and wait till you get it back.If you dont get it back in quite some time this means out of range.After you recive it (Or it times out) you reapet this proces

 

[pietjepuck]

You need to pulse the ultrasound,so there is time to wait for the reflected signal like electro-god says.
Unfortunately humidity and temperature will influence the speed of sound,which means the measurements may be differ.
Distance measuring this way is used in various industrial processes,but that equipment has circuitry to compensate for variations in ambient conditions.

 

[Alex_rcpilot]

Yea,I know I need to drive it with 40KHz wave and pulse the ultra.I saw an ultrasonic distance measuring instrument in the market today.Its nominal nearest range is 0.3m.So I don't think I can go with ultrasonic solution.

 

[mcs51mc]

Do you want to make one, or do you want to buy one?

If you have enough money to spend take a look at **broken link removed** high accurate, high speed all that you can dream of...

If you want to make one, read something about laser triangulation, optica, single array CCD, PSD (Position Sesitive Device).
Take a look at http://www.taosinc.com/category.asp?cateid=3 for the TAOS Linear array which give you an anlogue voltage proportional to the exposed pixel.

Hope this helps...

 

[panic mode]

Laser distance sensors are great and we use them all the time but they cost a lot (more than $1000USD). Here are some products we use with sample pricing (USD):

$8000 Keyence - LK503+LK-2503
$6000 MICRO-EPSILON - optoNCDT1700
$1200 Baumer - OADM20I4471/S14
$400 IFM Efector - O1D100

Beware the operating voltage, size and weight of the sensors if you plan on putting them on RC models.
The O1D100 is really neat product. It is very new on the market and I only bought about 30 of them so far. It is not only very inexpencive for a distance laser sensor but it is also very compact compared to some other solutions (Keyence sensor is as big as multimeter and controller is even bigger). It has display that shows measured distance in milimeters so you just need to power it up and you can use it as contactless measure tape. range is 200mm-10meter (up to 4m if target is black). Some cuts had to be made to bring such product for such low proce. For example update time is only 2-50 samples/sec (slower is more accurate) but this is something that is usually good enough. Accuracy on short range should be pretty close to what you are looking for. If you need better resolution, be prepared to spend more. I would be impressed to see DIY laser distance sensor that is more compact and more accurate even for fraction of range since one stil has to worry about things like optics etc.

 

[Alex_rcpilot]

Thanks guys! The info you provided are of grate value.I'm trying to build one,because distance measurement is just one function of the instrument I am building.I think I can go with the linear CCD solution,coz I can buy one right in the market around.