LPF Site Supporter
- Oct 7, 2018
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?
This is how I made mine, basically two batteries, a switch, and some plug in connectors placed in a project box.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:
Check this ebay auction. its an mW output measuring device for up to 120mW. Way cheaper to buy compared to a LaserCheck. Anyone got experience with such measuring devices? (Remove the "###" and copy paste link,.. i dont have link-posting rights, so i dont know another way to post it...)...laserpointerforums.com
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.