Page 3 of 3 FirstFirst 123
Results 21 to 30 of 30

Thread: Poor Man's Power Meter

  1. #21
    Join Date
    Aug 2011
    Location
    Alabama
    Posts
    270

    Default

    Click image for larger version. 

Name:	89644d1400376867-my-sharpness-test-results-tamron-150-600-a-yodapic.jpg 
Views:	2 
Size:	31.7 KB 
ID:	48755

    Pictures of laser setup needed.

  2. #22
    Join Date
    Feb 2011
    Location
    New Hampshire
    Posts
    3,513

    Default

    Never! It's mine, allllll mine! No... I must resist the dark side.

    A video to watch you will see. The Force in this one is great, but very patient you must be

  3. #23
    Join Date
    Nov 2014
    Location
    mid michigan
    Posts
    814

    Default

    ahhh, shiny lasers, i must have! I you have shiny laser, yes?

    I some times roleplay an Arakkoa in world of warcraft, they are a birdlike race that some times speak in broken up order as well.
    you need screen shot yes?

    Click image for larger version. 

Name:	Outcast_Harbinger.jpg 
Views:	8 
Size:	137.7 KB 
ID:	48756

    for green laser i have used green leds for a cheap indication of power, the meter with an led is hard to hit with the beam as you need to hit the ship inside, and the led is directly connected to a mechanical panel meter. I have a small pocket meter that uses a type of silicon detector for lower power stuff, it's max is 40mw, sper scientific they are about 200 bucks and for higher power i use a prism or a mirror that transmits about 6% of light though the reflective layer on the mirror
    Remember Remember The 8th of November, When No One Stood, but Kneel, In Surrender
    In a popular government when the laws have ceased to be executed, as this can come only from the corruption of the republic, the state is already lost. Montesquieu

  4. #24
    Join Date
    Feb 2011
    Location
    New Hampshire
    Posts
    3,513

    Default

    I am waiting to play with the Molectron head that Steve linked me to. I am pretty sure that it's wavelength response will be flat. Once I have its response vs energy compared to my vacuum calorimeter at some reasonable number of joules (this will probably require the wedge sampler as well) then I can measure absolute joules. I trust the calorimeter because everything goes in and much less than 1% comes out.

  5. #25
    Join Date
    Feb 2011
    Location
    New Hampshire
    Posts
    3,513

    Default

    Steve,
    I got the head. I am impressed that it works with the entire 75mm front surface. Do you usually run these through a parallel resistor (to drain the accumulated charge) as opposed to simply into the 10Mohm input of an O-scope? I assume I need to integrate the area under whatever curve is generated.

  6. #26
    mixedgas's Avatar
    mixedgas is offline Creaky Old Award Winning Bastard Technologist
    Infinitus Excellentia Ion Laser Dominatus
    Join Date
    May 2007
    Location
    A lab with some dripping water on the floor.
    Posts
    9,890

    Default

    Click image for larger version. 

Name:	AN_202194_Photo_or_Pyro.pdf 
Views:	16 
Size:	155.4 KB 
ID:	48760Attachment 48762Click image for larger version. 

Name:	OdonJoulemeter.pdf 
Views:	11 
Size:	98.2 KB 
ID:	48759\\

    .
    .
    .
    Generally, I check with the company and get the data sheet. If its a 10 Meg rated head, I use the scope as is if it is a 10 meg impedance. If its a 1 Meg rated head, I add the termination resisitor. If the head is a 10 meg head and the scope was 20 meg, of course I'm adding a parallel resistor.
    .
    Generally I dont integrate, I just look at the peak to peak signal. However you can integrate... My previous employers all provided Joulemeter readouts, I use a scope at home only.
    .
    Please see attached..
    .
    Odon, from Measurement Science Review, posted under Educational use clause. Found on web in random search.

    .
    Just dont burn the surface. Reblackening them with flat black engine paint does not hurt accuracy much, but deeply damaging the adsorber disk is frowned up. Slightly burned sensors turn grey and loose accuracy..
    On most of them, there is NO slack in the rated damage threshold...
    .


    Steve
    Last edited by mixedgas; 10-25-2015 at 17:20.
    Qui habet Christos, habet Vitam!
    I should have rented the space under my name for advertising.
    When I still could have...

  7. #27
    Join Date
    Nov 2014
    Location
    mid michigan
    Posts
    814

    Default

    quick question from the peanut gallery, what do these shinies cost? and can they work cw? i will read the full pdf but did not have the time tonight?
    cheap i hope, yes!
    Remember Remember The 8th of November, When No One Stood, but Kneel, In Surrender
    In a popular government when the laws have ceased to be executed, as this can come only from the corruption of the republic, the state is already lost. Montesquieu

  8. #28
    Join Date
    Feb 2011
    Location
    New Hampshire
    Posts
    3,513

    Default

    The head I bought cost $50. It has a small burn on the surface that I suspect may affect the accuracy, but I'll experiment to see if the output depends on the location of the pulse. For your experiments with bright, but diffuse flash lamps, a biased photo diode works well. Fed into an oscilloscope, you get nsec time resolution and a smooth, easy to interpret curve. You can use selective wave band filters or stacked neutral density filters to bring the input to within the useful range of the detector.

    I have several different models for different wavelengths. I'm sure you can purchase them on eBay, however I bought my favorite, the DET100A, from Thorlabs for about $150.

    http://www.thorlabs.com/newgrouppage...tgroup_id=1295

    If you get into these flashlamps, see how bright they can be and decide to use them to drive a crystal such as ruby, alexandrite, YAG or a dye, then I think the output would be suited for the joule meter.

  9. #29
    mixedgas's Avatar
    mixedgas is offline Creaky Old Award Winning Bastard Technologist
    Infinitus Excellentia Ion Laser Dominatus
    Join Date
    May 2007
    Location
    A lab with some dripping water on the floor.
    Posts
    9,890

    Default

    Did you mean Thorlabs DET10A??? My favorite is the DET10A with the 1 nanosecond response...

    Pyroelectric Joule meters are for pulsed lasers. For CW lasers you need to use a chopper wheel to pulse the beam for a Joule Meter, as the sensor only responds to pulses. Laser show folks are better off with a photodiode or thermopile detector head both of which handle CW beams just fine...

    Steve
    Qui habet Christos, habet Vitam!
    I should have rented the space under my name for advertising.
    When I still could have...

  10. #30
    Join Date
    Feb 2011
    Location
    New Hampshire
    Posts
    3,513

    Default

    No, I like the 100A because of it's large detector area. The slower response time is fine for my usec lasers. I use the DET25K for the blue response and when response time will matter then this should work for my visible lasers despite its blue sensitivity.

    Laser show folks are better off with a photodiode or thermopile detector head both of which handle CW beams just fine...
    Agreed

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •