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LPM only with Temperature sensor ?

fricek12

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Is it possible to measure Laser output power with Temperature Sensor ?

eg. datasheet: http://www.gme.cz/_dokumentace/dokumenty/313/313-909/dsh.313-909.1.pdf


I have seen Laserbee LPMs and LPM based on IR thermometer and piece of aluminium foil, but what about to use Temperature sensor and digital Multimeter (or thermal resistor with digital multimeter - how to convert/calculate mA or Ohm to mW)?

Is it possible ? How ?

Thank You
 
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I'm not sure how you would make this work. First of all laserbee LPM's use a TEC to get power readings, they don't use any form of IR. IR thermometers work by picking up BB radiation. If you gave a better explanation of how you expect this thing to work we would be better able to figure out if it would work.
 

lasersbee

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Is it possible to measure Laser output power with Temperature Sensor ?

eg. datasheet: http://www.gme.cz/_dokumentace/dokumenty/313/313-909/dsh.313-909.1.pdf


I have seen Laserbee LPMs and LPM based on IR thermometer and piece of aluminium foil, but what about to use Temperature sensor and digital Multimeter (or thermal resistor with digital multimeter - how to convert/calculate mA or Ohm to mW)?

Is it possible ? How ?

Thank You
If it could easily be done with accurate results we would
all be doing it...:beer:


Jerry
 
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Bluefan

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Sticking a tec to a heatsink with some black paint isn't very difficult. Calibration is another story, that needs a lpm for comparison (chicken egg problem) or or some super complicated calorimeter setup like the NIST hast.

NIST has a Laser Optimized Cryogenic Radiometer with 0.02% accuracy as standard and uses an Electrically Calibrated Pyroelectric Radiometer (ECPR) as laboratory standard. Laser Precision developed these ECPR's, my Laser Precision radiometer has a 1.5% + 0.5%FS calibration accuracy, very good for an optical measurement.
 

fricek12

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I'm not sure how you would make this work. First of all laserbee LPM's use a TEC to get power readings, they don't use any form of IR. IR thermometers work by picking up BB radiation. If you gave a better explanation of how you expect this thing to work we would be better able to figure out if it would work.

I suggested to use e.g. thermal resistor. (the higher temperature, the lower resistance) and measure it with multimeter how much its resistance get lower. Then need to calculate the temperature (before and after). But dont know how to convert the rise of temperature in certain material the resistor is made of to power (W).

edit: it is called thermistor in English
en.wikipedia.org/wiki/Thermistor

I will check the method with TEC module.

Thanks.
 
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Bluefan

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Thermistors probably won't work very good but of course some experimentation can show how well they behalve.
 
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Well if you knew
1.% reflected and the amount absorbed for the wavelength
2. Dot size
3.Thermal capacity of the material and how much it heats up from the laser
With all that you can derive the power of the laser.
 

Bluefan

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Well if you knew
1.% reflected and the amount absorbed for the wavelength
2. Dot size
3.Thermal capacity of the material and how much it heats up from the laser
With all that you can derive the power of the laser.
What you're looking for is how either the steady state situation or the linear regime. In the first case there's a balance between absorbed radiation from the laser, absorbed radiation from the surroundings (background), electrical heatink by the test current and radiative losses, conductive losses and convection losses. A lot of them are sensitive to the lcoation of the laser on the thermistor.

Int he linear situation the assumptopn is that the temperature difference between the thermistor and the surroundings is negligible and that the temperature increase is linear with the applied power. This still requires knowledge of the conductive losses but also of the heat capacity.

Rather hopeless I'd say, not because of the many unkowns (which can be calibrated) but because of the large position sensitivity of the parameters.
 




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