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DMM power meter?

Anthony P

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I just watched video of a member using a power sensor attached to a DMM. How does that work? Where can I find more information?
 



FAP

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Likely, the DMM is set to DC voltage and is just measuring millivolts, the power sensor puts out some number of millivolts per watt, see a thread on this here:


LPM heads which do this use what is essentially a thermo-electric cooler module which has diode junctions sandwiched in the middle of two ceramic plates, one side thermally coupled to a heat sink, the other the side is the surface a laser beam will heat, as you shine it on the head window, or rather, aperture, usually painted dark, or with some dark substance adhered to it to help absorption across a range of wavelength.

The temperature differential between the plates produces a voltage across the diodes you can measure (up to a point, once that heat sink warms up too much, the temperature difference is diminished and you will then no longer have accurate readings). Some heads have a linear relationship to millivolts, others require a conversion chart, or a circuit board which converts the mv reading to a digital value to correspond to the power.
 
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Alaskan

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I reset my password using my iPhone to answer this post and didn't know I had my first LPF account associated with that email account from 2013 and posted this without seeing I was using my old account. Now I'm using my notebook and have emailed Avery asking him to please combine both accounts.
 
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Alaskan

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Yes, we are not allowed to have two accounts, that's why I asked to combine them together, no answer yet though. When I responded, I didn't see what happened, that I had reopened an old account. I couldn't understand how "FAP" had posted what I wrote, then I saw what happened. I had completely forgot about having created that account.
 

BowtieGuy

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Likely, the DMM is set to DC voltage and is just measuring millivolts, the power sensor puts out some number of millivolts per watt, see a thread on this here:


LPM heads which do this use what is essentially a thermo-electric cooler module which has diode junctions sandwiched in the middle of two ceramic plates, one side thermally coupled to a heat sink, the other the side is the surface a laser beam will heat, as you shine it on the head window, or rather, aperture, usually painted dark, or with some dark substance adhered to it to help absorption across a range of wavelength.

The temperature differential between the plates produces a voltage across the diodes you can measure (up to a point, once that heat sink warms up too much, the temperature difference is diminished and you will then no longer have accurate readings). Some heads have a linear relationship to millivolts, others require a conversion chart, or a circuit board which converts the mv reading to a digital value to correspond to the power.
This is how I made mine, basically two batteries, a switch, and some plug in connectors placed in a project box.
The green dots are where the switch is.

 

Alaskan

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Ditto, same I have too.
 

paul1598419

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Yes, that Ophir head needs a positive and negative rail to power the sensor. The greater the difference the higher the power it will read. Up to a point, anyway.
 

lasersbee

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Don't forget that the split supply should be very close
to the same + and - voltage and a max of 18VDC each
side on that OPHIR 20C head.

Jerry
 




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