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ArcticMyst Security by Avery

some questions and reflections on the laser power meters

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If In fact Most powermeters simply are based on the principle that the optical power is converted to heating power in some absorber structure, Ignoring those based on photodiodes obviously.

Why usually so expensive?

Is possible to make one using an electronic thermometer or something like it?

:thanks:
 





Trevor

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You can build a TEC based one with datalogging for less than $75.

As a starting point, check out the <$50 meter that MarioMaster posted schematics to. :)

-Trevor
 
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If In fact Most powermeters simply are based on the principle that the optical power is converted to heating power in some absorber structure, Ignoring those based on photodiodes obviously.

Why usually so expensive?

Is possible to make one using an electronic thermometer or something like it?

:thanks:

Here is a link to some DIY LPMs.... If you come up with
something better... don't forget to post it on the Forum...:wave:

http://laserpointerforums.com/f39/laserbee-i-thermopile-based-laser-power-meter-40116.html


Jerry
 
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If In fact Most powermeters simply are based on the principle that the optical power is converted to heating power in some absorber structure, Ignoring those based on photodiodes obviously.

Why usually so expensive?

Is possible to make one using an electronic thermometer or something like it?

:thanks:

I hope so. Because i don't like spending more money on the meter than on my laser. :)
 
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Speaking of that thread, two good links to add would be MM's $50 LPM and knimrod's open-source LPM interface. :thanks:

-Trevor

Speaking of that old thread... with a little closer reading you
would have seen that Knimrod's LPM Interface is already
linked there...:beer:
BTW... it is not all open-source... the Data Logging Firmware
source code and PC Interface source code were not
open source......

Jerry
 

Trevor

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I didn't link to that part because the programmed MCU is
no longer available and the Link I supplied has the Schematic
for hooking up the surplus Coherent head that also is no longer
available... but the schematic could be used with some other
new or surplus heads...

Jerry
 

Trevor

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I didn't link to that part because the programmed MCU is
no longer available and the Link I supplied has the Schematic
for hooking up the surplus Coherent head that also is no longer
available... but the schematic could be used with some other
new or surplus heads...

Jerry

Ah ok, thought it might be relevant. Guess not. :p

MM's is definitely useful though, if you wouldn't object to adding it. :)

-Trevor
 
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MM's DIY circuit is what he is using in his Alpha...

The Alpha is a commercial product...

The title of the link I gave to the member above is:-
LaserBee I Thermopile Based Laser Power Meter

I would be shooting myself in the foot to start advertising
a competitors products under my flag... :cool:


Jerry
 

Trevor

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MM's DIY circuit is what he is using in his Alpha...

The Alpha is a commercial product...

The title of the link I gave to the member above is:-
LaserBee I Thermopile Based Laser Power Meter

I would be shooting myself in the foot to start advertising
a competitors products under my flag... :cool:


Jerry

Sorry, I thought that since he hadn't rushed to delete the thread after commercializing that he wouldn't mind people still building it. Though... it would theoretically be in your best interests to have someone build one rather than buy one from him... ;)

But, after looking at the thread again it seems the links to the images are now dead. Moot point then. :whistle:

-Trevor
 
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I just looked on MM thread and yeah ... he's seems to have
changed his mind about sharing the Alpha circuit with the
Forum... I guess he must have just made a mistake posting
it... IIRC... the Alpha didn't come out for quite a while after
that schematic was posted...:thinking:

I have a copy of that deleted Schematic if anyone really needs
it...:beer:

Jerry
 
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Thank you very much for your help, trevor.

Hi Lasersbee, I’m considering buying your LPM but now I have no money at the moment, but for the comments on the forum your LPM work very well :)

I think faster and more sensitive powermeters can be made with photodiodes, but the great problem is their sensitivity is rather wavelength-dependent (correct me if I'm wrong)

:thanks: :thanks:
 

HIMNL9

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^ no, you're right, photodiodes are very fast, and there are some of them made very large for be used as laser power meters, but they have a sensitivity curve dependent from the wavelenght (also the so-called "blue enhanced photodiodes" have a very large variation in the sensitivity curve) ..... the only way for get a "linear" (almost linear, at least in a certain range) response curve, is to place in front of them a dichroic filter that have a transmissivity curve exactly opposite of that of the diode, so it can "flatten" the more possible the response curve, making it the lower possible for the more part of the wavelenghts ..... but a similar dichroic filter, can end costing more than the photodiode itself, if made "on request" :p

Also, they have the bad abitude to suddenly die when you point a focused beam on them (mean, focused for burn) ..... opposite than calorimeters, TECs and thermopiles, that can have a small part of the surface ruined from a burning spot and continue to work good, a photodiode that become hit from a burning spot, usually go in short circuit and you have to throw it away.
 




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