laser measuring devices

[Steve B]

Do they work very well, or are they just for guesstimating?

Steve

[mm]

Don't know, but you could take some known distances and verify the one you buy. Seems to me one should do that anyhow, in case you get a bad one.

When I buy an egg-timer, the one with sand for example, I could have used a watch, but instead I flipped over several and compared them with each other. I bought one of the group that matched each other.

(although actually they were all very close. The worst might have been 5 seconds over two minutes, and almost all were within a second or two of each other, and these were cheap ones, 20 years ago.

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[Paul Franklin]

There are two types. One use the laser to actually make the measurement. They are quite accurate. The other type uses the laser as a visual aiming aid only, and uses ultrasound to make the measurement. They are a lot less accurate (say within a few inches at

50 feet distance or so) and are more prone to measuring the wrong distance, like to intermediate obstacles for example.

The first type run $350 and up, the second start under $100.

Paul

[Steve B]

Then mine, probably some of the cheapest you can buy would be on a par technologically with a string and a tin can?

Probably.

But, I was going to go out and do some comparisons with a hard tape, and this thing. The major thing I can see is that it won't take a reading in bright sunshine. A problem here in Las Vegas, where it was 70 degrees here on Christmas Day. But cloudy.

Steve

[RicodJour]

Is that the LV version of a white Christmas? ;)

R

[siralfred]

I took a look at the Stanley level at HD and it says right on the box that the accuracy is limited to 1/2" over 10' which is not enough to comply with ANSI standards for ceramic tile installations. It would probably be visible to some people if say, a 5' shelf was 1/4" out of level. So these products are not any better than just eyeballing. But that's the level. My point is just that the cheap ones aren't accurate enough to be useful to anyone.

[upand_at_them]

Are you sure there are ones that measure by laser? Ultrasound ones use the bounced back wave to figure out the distance. To do this with a laser would require an extremely fast processor...we're talking supercomputer.

Mike

[Jim Elbrecht]

-snip-

I bought one of the second type when the borg lowered the price from $45 to $15. I've gotten $5 worth of entertainment from it. I consider the other $10 the cost of 'lessons learned'.

Because they use sonar, the texture of a surface throws it off. How squarely you hit the surface also affects it- often in some weird ways. Playing with it, I think there are more variables, but all in all I wouldn't ever trust a critical measurement to it.

Never used the other type.

Jim

[Steve B]

It shines a little red dot at whatever you point it at. Is that an ultrasonic dot? Or a little laser pointer, and then the distancing device is ultrasonic?

Steve

[Ralph Mowery]

Look at the end of the device where the laser light comes out. If there is a big round hole that looks like a funnel and another smaller hole where the laser light comes out, it is the ultrasonic type with a laser pointer that gives the general direction of the aiming point. Also it may make a clicking sound.

[Edwin Pawlowski]

This one is an ultrasonic with laser pointer

This one states it measure with the laser

Product Description: The TLM 100 Tru-Laser? distance measurer gives you ?Tru? laser measuring at the press of a button ? just point, press the button and measure indoors, outdoors and hard-to-reach areas. Tru Laser technology actually measures the laser light travel distance.

Read about the technology here

[Paul Franklin]

Sure, here's a link:

If you read the faq (there's a link on the above page), they go into a little detail about looking at the phase shift of the returned pulse train. Using a phase comparison of two pulse trains (emmitted and returned) avoids having to have a processor fast enough to measure the round trip time of a single pulse. Rather clever, actually...

Paul

[upand_at_them]

Light travels 3.0 x 10^8 meters per second. Measuring 1 meter (3.3 feet) and ignoring the time taken to perform calculations would take

3.3 x 10^-9 seconds. Giving the benefit of the doubt and assuming it takes two processor instructions to recognize the returning light wave (that is, process two instructions in the given time) the speed of the processor is then 6.0 x 10^8 Hz, or 600 MHz. Microcontrollers don't run this fast and I doubt there's a Pentium in there. The laser is probably just a pointer so you know what your measuring to.

Mike

[Steve B]

That explains it. What I have is a POS toy, and not a really accurate measuring device.

Thanks to all.

Steve

[Chris Lewis]

According to Paul Franklin :

How soon people forget analog ;-) Or non-programmable digital for that matter. Custom ASIC running at a couple Ghz is easy, and very cheap in quantity. It's essentially a frequency counter.

[Paul Franklin]

Even if you have a laser guided ultrasonic unit and not a true laser (see the other posts) it's still pretty handy for quickly measuring room sizes for extimating materials, etc.

Can you use it to measure how long to cut that next pece of crown molding? No. But you can use it to know how much crown molding to buy, or carpet, or paint, etc...

So don't toss it yet...

Paul

[upand_at_them]

Cool, thanks for pointing that out. I learned something new.

Mike

[Bishoop]

You might want to check out this link to Stanley Tools laser/ultra-sonic measuring device.

If the specs are correct, +/- 1/4 inch over 100 feet is not too bad.

[Stubby]

That's how GPS works. They match up a 1023 bit random string of bits to get the high accuracy after a course measurement by more standard techniques.

[mm]

Very interesting. The funnel is much bigger than I thought was being talked about. I thought it was like a quarter inch at the top, instead of 2 or 3 inches.

very annoying. They won't tell you the price until you put it in the shooppping cart.

Amazon Visa discount: - $30.00 Your new subtotal: $64.94 Save $30 off your first purchase, earn up to 3% rewards, get a 0% initial APR, and pay no annual fee After just 2,500 points you'll get a $25 Amazon.com Reward Certificate.

Chuck Schumer, the senator, was talking about this in NYC a few weeks ago, about how store credit cards charge about TWICE the rate that bank credit cards do. He mentioned the ones like this one that give you a discount off your first payiment. Notice how many details this gives, but doesn't give the rate. Sleezy. Unbefitting a company like Amazon which is trying to establish a good reputation. Now it looks as sleezy as anyone else.

This is why I had all the questions about the telephone sservice advertized here earlier (spam.).

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