What's really the best LPM?

BobH said:

I'd like to know too! The Zap-It paper measures (more accurately, indicates) the energy distribution across a beam. It's a "paper meter". The razor blade indicates roughly the energy in a beam. I wonder if there might be some other technique or commonly available device or material that can be used to know if a laser beam is 1, 5, 10 or 50 mW easily, and without a specialized meter available to the user?

First thing I'd propose is identification. If you know what the laser is and who made it, ask them. That'll tell you the ballpark. Is there any reason to think the laser's not up to full power? What color is the beam?

After that, a few questions: Can the raw beam burn anything? Can the focused beam burn anything? Black electrician's tape? Can you point it into your finger? How long can you hold it there? Can you see the light go through your finger? Through the meat of your hand?

I think that with all the experience here with laser pointers that a "calibration" of an "experiential meter" might be possible. I wonder how accurate such a procedure can be? I know I can tell if a beam's 1, 10, 100 or 500mW just by looking at it. How accurate does it need to be? 1mW is benign, 100mW isn't. I'd want to know if my child is playing with 1, 10 or 100mW. If the "100mW" laser I just bought as my first laser is only giving 50mW, I'd want to know.

Click to expand...

It seems that the Zap-It product is used for pulsed Laser measurements...
If you use a CW laser you will need to build a Beam Chopper with know beam
pulse rate and duration... That precise Beam Chopper should be cheap to build...

Using ZAP-IT Paper

It is well documented on the Forum that lasers (mostly From China) are
not exactly as they are advertised (power wise)....
Example....
http://laserpointerforums.com/f38/inexpensive-blu-ray-laser-pens-worth-look-46487.html

If a member on the Forum sells a Laser here...he can state the approximate
power by other member's tested experience.. using the mA the Driver is set at
for a particular Laser type.

I have a 100mW Red Laser that can not burn wood....
I have a 30mW Blu-Ray Laser that can...:thinking:
So which one is more powerful...

Actually what you want to know is that if you bought a relatively safe 5mW laser
for your child... that it is NOT outputting 35mW or greater...

As to an inexpensive Laser Power measurements....
a bit of research on the Forum would have netted you these DIY projects...

http://laserpointerforums.com/f42/simple-laser-power-meter-using-ir-thermometer-26341.html

http://laserpointerforums.com/f42/diy-laser-power-gauge-26332.html

http://laserpointerforums.com/f42/diy-laser-power-meter-26831.html

http://laserpointerforums.com/f42/led-photo-diode-laser-power-meter-26827.html

Any if these have more potential for close approximations of Laser Power
than the Zap-It product.... IMO..

As I've stated in other posts.... using burning capabilities as a way
to measure Laser Power (besides all the variables burning with a Laser
involves) is like measuring wind speed holding a wet finger into the air...


Jerry

Thanks once again lasersbee

That's what we are here for...

Jerry

BobH said:

All those links except the last one are to very good examples of how to build a thermal meter. I was talking about more "organic" ways to indicate power, for those not interested in electronics projects. May be too "touchy feely" for you. Sometimes a finger in the wind (or the beam) is all that's necessary.

Click to expand...

But only useful in knowing that there is a wind blowing and which general direction it flows. Imprecise is too gentle a word for the method mentioned.

Peace,
dave

Thermopile Laser Power Meters measure a temperature differential between the
Heatsinked Head and the Sensor Surface...
They do NOT measure "Burning capabilities"...

"Burning capabilities" are dependant on the Energy density of the Beam and the
way it is focused on the surface area and the beam Wavelength in conjunction
with the the color... texture.. and material that is being burned... not to mention
the material's heat dissipation factor...

That also has been discussed in numerous Threads on the Forum....

Jerry

I usually keep up with my threads but I think I am going to have to let this one go. I got a little confused a few posts ago. lol

[Sarcastic]
Thanks for clearing that up for us noobs....
I wasn't aware that a 100 Watt Laser could burn better than a 100 MilliWatt
Laser...:thinking:
[/Sarcastic]

I merely responded to your posts with my opinion and knowledge
pertaining to the data that you supplied...


Jerry

>>The let out your aggression thread <<

You can stop:horse:....anytime...

Jerry

If your talking to me, I was just giving advice.

Scotty 757 said:

If your talking to me, I was just giving advice.

Click to expand...

Nah... that was directed to the "Expert"...
You just typed too fast...


Jerry

I'm not saying people with low amounts of posts don't know anything but I have never seen someone with little post argue with a vet who from the looks of it knows what he is talking about.

BobH said:

"Ballpark" was my destination. And aren't all thermal detectors measuring the "burning capabilities" (albeit with a target that can take the heat) of lasers? Just a more sensitive "finger in the wind"?

Click to expand...

I guess if by "ballpark" you mean can you tell that the laser is "on" and that the light is hitting a surface, then I would agree. However, most people can do that by just looking at it.

Reductio absurdium works both ways, Mate

Peace,
dave

BobH said:

30 years of experience measuring laser beams ... yes, I AM an "expert" with that.

Click to expand...

I guess the next thing you'll share with us it that you measured these
Laser for 30 years using your finger... or some burning scale...

It's not how long the road... but what you learn on your journey...


Jerry

Scotty 757 said:

I'm not saying people with low amounts of posts don't know anything but I have never seen someone with little post argue with a vet who from the looks of it knows what he is talking about.

Click to expand...

LOL. That's just ego, and notice how often it leads a thread off topic. They remind me of my late Dad's favorite saying, "People who think they know it all are particularly annoying to those of us that do."

You hit on a good related point, too. An expert on all things laser related could conceivably join the forum, and likely shake his or her head at all the "amateurs" here. No offense intended to you amateurs with 1000+ posts. No one should judge a member based on number of posts alone. But it is often true that newer members seem to have those egos. There are also a lot of experts here with ego issues.

Roosl just contributed to being off topic.

Back on topic.. As someone mentioned, the best LPM (for you) is probably decided by (your) needs. As a hobbyist with no intention of building and selling lasers, I decided on Ken's new USB model. That's the "best LPM" for me.

Very good point roosl. It was idiotic of me to refer to the posts amount. But lasersbee sells LPMs I thought so I figured he knew something about them. Back on track the Kenometers do look good. I am considering the Kenometer PRO.