Simple Laser Power Meter Using IR Thermometer

[Vaporizer]

drummerdimitri,
You won't be able to use any number anyone else posts IMO.
There are just to many differences that can occur. That was my main point & finding. You have to have a standard to make one.
Paint type, reflectivity, absorption, thickness, target size, there are just so many places for error.
Also, it is a "low mass" target, so it's susceptible to change from outside influences easily.
Best you can hope for if you have everything is just to make it and have someone calibrate a laser you have. Best if you had a couple of them done in a wide range. Say 20mw & 100mw. Depends on the range you want to check.
You can tell how much more power each of yours has by % comparison if you do make it and IR filter % loss. Things like that.

I can's see anyone posting an exact number and saying "use this" unless they were providing the target they checked and gave the value to use. That still doesn't eliminate mounting errors, gap, target coverage and such.
I don't think within 10% is unreasonable, but on a 1-1.5W laser that is still a lot.
Make yours for now and enjoy it as a comparator. It is fun and a good learning experience from your observations.

 

[drummerdimitri]

drummerdimitri,
You won't be able to use any number anyone else posts IMO.
There are just to many differences that can occur. That was my main point & finding. You have to have a standard to make one.
Paint type, reflectivity, absorption, thickness, target size, there are just so many places for error.
Also, it is a "low mass" target, so it's susceptible to change from outside influences easily.
Best you can hope for if you have everything is just to make it and have someone calibrate a laser you have. Best if you had a couple of them done in a wide range. Say 20mw & 100mw. Depends on the range you want to check.
You can tell how much more power each of yours has by % comparison if you do make it and IR filter % loss. Things like that.

I can's see anyone posting an exact number and saying "use this" unless they were providing the target they checked and gave the value to use. That still doesn't eliminate mounting errors, gap, target coverage and such.
I don't think within 10% is unreasonable, but on a 1-1.5W laser that is still a lot.
Make yours for now and enjoy it as a comparator. It is fun and a good learning experience from your observations.

You are right Vaporizer, there are too many variables in this experiment that can alter the results drastically. The only problem is that no one on LPF lives in my country, so I cant have someone calibrate my laser for me. That wont stop me from trying the Experiment out! I already have an idea of the output of two of my lasers, so I will work from there to create my own "magic number" that will work with other lasers too. Like you said, there are a lot of things to learn from this, and mistakes is definitely one of them! Thanks for your elaborative reply!

 

[dnar]

I used this method to determine the best operating temperature of my 150mW 532 labbie last night. I set the IR thermometer up to stay on so i did not touch or move it, tweaked the TEC setting, re-checked ever 15 minutes and finally found the magic temperature of 26-27oC.

It is good for "relative" measurements...

 

[Vaporizer]

Another good use found there Wayne.

 

[RayBurne]

I have repeated a full range of experiments using a uniform target material, a uniform mass of carbon shellac, and a very accurate (0.02C) recording thermometer and have determined that temperature rise of a uniform black target of uniform mass and specific-heat can be utilized as a LPM. However, just like an LPM, it must be calibrated with an LPM... there is no free lunch.

Once the equation for tracking temperature rise to thermal energy is derived, it can be applied to a separate target with identical construction with identical (at least to my ability to calculate) results. I wish I could have proven the initial claim that a simple constant can be utilized, but the math requires a 3-rd order algebraic equation to provide accuracy.

I hope my tests and results provide some closure on this concept. I encourage others to experiment and post results in the Experimental section. Collectively, shared information advances our knowledge of such relationships.

Here are my results: http://laserpointerforums.com/f42/h-e-t-light-coherent-64606.html#post928183

- Ray

A very special thank-you to LasersBee for the design and implementation of the new USB LPM with PC recording capability. Without his affordable technology, I could not have created my experiments and certainly could not have validated any relationships.

 

[PhoenixOrion]

I tried this I have the big IR thermometer and the gun type one in the photo that shows several different ones. I did the calculations and it says that my 300mW green FireDragon is 71mW and the my M140 solarforce that I just got off of danafex is only 576mW but before he sent it to me it was over 1500mW. I noticed on the gun type one that I have that the sensor is way back in the housing so there is no way for me to get it 1/16th of an inch from the sensor. Maybe the circular one??? How to cut a perfect circle that size?

 

[lasersbee]

I tried this I have the big IR thermometer and the gun type one in the photo that shows several different ones. I did the calculations and it says that my 300mW green FireDragon is 71mW and the my M140 solarforce that I just got off of danafex is only 576mW but before he sent it to me it was over 1500mW. I noticed on the gun type one that I have that the sensor is way back in the housing so there is no way for me to get it 1/16th of an inch from the sensor. Maybe the circular one??? How to cut a perfect circle that size?

If the Laser shipped to you was 1500mW and you verified it
with your DIY LPM then I would seriously suggest that your
DIY LPM is obviously NOT calibrated correctly...


Jerry

You can contact us at any time on our Website: J.BAUER Electronics

 

[DrSid]

Distance of the thermometer should not matter.

Major effect here is cooling of the metal target by air. It's rather unpredictable. Not only it depends on room temperature and humidity, but as the air gets warmed by the target, it will start to move .. and cooling effect will depend on aerodynamics of the surroundings of the target. It would be best if the target could be placed in vacuum .. but that's not so simple, is it ..

I dropped this method completely. It's good for very basic comparison of not very strong lasers .. but I would not call that metering.