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

Steve

On Sat, 24 Dec 2005 21:38:21 -0800, "Steve B"
wrote:

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

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.

Steve



Remove NOPSAM to email me. Please let
me know if you have posted also.

On Sat, 24 Dec 2005 21:38:21 -0800, "Steve B"
wrote:

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

Steve


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

"Paul Franklin" wrote in message
...
On Sat, 24 Dec 2005 21:38:21 -0800, "Steve B"
wrote:

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

Steve


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


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

Steve B wrote:

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.

Is that the LV version of a white Christmas?

R

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.

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

Paul Franklin wrote:
-snip-
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.


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

wrote in message
ups.com...
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


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

"Steve B" wrote in message
news:SfJrf.8594$_L5.2290@fed1read06...

wrote in message
ups.com...
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


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

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.

"Steve B" wrote in message

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

This one is an ultrasonic with laser pointer
http://www.amazon.com/gp/product/B00...lance&n=228013


This one states it measure with the laser
http://www.amazon.com/gp/product/B00...antInformation

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
http://www.stanleytools.com/default....FT=left_pr.htm

On 25 Dec 2005 18:06:18 -0800, wrote:

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

Sure, here's a link:

http://www.leica-geosystems.com/cpd/.../lgs_31658.htm

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

Steve wrote:
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?

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

wrote in message
oups.com...
Steve wrote:
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?

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


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

Thanks to all.

Steve

According to Paul Franklin :

Sure, here's a link:

http://www.leica-geosystems.com/cpd/.../lgs_31658.htm

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...

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.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.

On Sun, 25 Dec 2005 20:22:41 -0800, "Steve B"
wrote:

snip


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

Thanks to all.

Steve

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

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

Mike

wrote in message
oups.com...
Steve wrote:
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?

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

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.

Paul Franklin wrote:
On 25 Dec 2005 18:06:18 -0800, wrote:


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


Sure, here's a link:

http://www.leica-geosystems.com/cpd/.../lgs_31658.htm

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...

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.

On Mon, 26 Dec 2005 03:48:51 GMT, "Edwin Pawlowski"
wrote:


"Steve B" wrote in message

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

This one is an ultrasonic with laser pointer
http://www.amazon.com/gp/product/B00...lance&n=228013

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.

This one states it measure with the laser
http://www.amazon.com/gp/product/B00...antInformation

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.).

Remove NOPSAM to email me. Please let
me know if you have posted also.

Chris Lewis wrote:
According to Paul Franklin :


Sure, here's a link:



http://www.leica-geosystems.com/cpd/.../lgs_31658.htm



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...


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.

I imagine it is similar to the method of measuring
the thickness of very thin sheets or coatings.
You can do it using interference colors (like the
colors you see on an oil slick). Don't even need
any measurement equipment except your eyeball
since the reflected color varies with the
thickness. Color blind people not allowed.

In article .com,
says...
Steve wrote:
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?

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.

What makes you think a processor has to do the measurements in
software? That would truly be dumb. Time measurements in the 1ns
range aren't difficult at all, though I agree this isn't what
they're doing. Measuring even to 1ns is 1 foot accuracy; hardly
useful.

Keith Wiliams wrote:
What makes you think a processor has to do the measurements in
software? That would truly be dumb.

No, what would truly be dumb is to reply when you don't know what
you're talking about. The measurement IS being done in software.
Where else is it going to be done? Do you think the light wave
computes the distance itself and passes the data to the microcontroller
to display it?

The microcontroller has an on-board timer and uses it to measure the
phase difference, in time (T). But instead of measuring the time for
the lightwave to bounce back, the phase shift is measured (in TIME).
The transmitted frequency (R) is known so it then computes D, where D =
R x T.

Mike

In article .com,
says...
Keith Wiliams wrote:
What makes you think a processor has to do the measurements in
software? That would truly be dumb.

No, what would truly be dumb is to reply when you don't know what
you're talking about.

Nice, but ignorant comment.

The measurement IS being done in software.

That would truly be dumb. Hardware can easily measure a
nanosecond. Software can format the output of the hardware so a
human can read it, but a software timing loop differentiating 1ns
events? You're on drugs.

Where else is it going to be done? Do you think the light wave
computes the distance itself and passes the data to the microcontroller
to display it?

You really are ignorant. Have you ever considered a simple counter
running at a GHz, or maybe interferometry to measure the phase
relationship of the sent and received signal. The microcontroller
certainly *not* going to be able to discern a 1ns signal, even it
it does operate at a couple of GHz.

The microcontroller has an on-board timer and uses it to measure the
phase difference, in time (T). But instead of measuring the time for
the lightwave to bounce back, the phase shift is measured (in TIME).
The transmitted frequency (R) is known so it then computes D, where D =
R x T.

The timer would have to operate at a GHz, along with the I/O in
question, just to get one *foot* resolution. Hardware can be used
to measure the phase relationship without having to operate at
20GHz (1/2 inch).

--
Keith