billg519
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A little while back, I had a thread going about an LPM I made with a small TEC and a small analog panel meter. This simple device proved reliable and repeatable, so why not make something to attach to a DMM? I found a small black square heatsink from a junked PC and attached the small TEC to it. The TEC was coated with black sharpie marker this time. Since I needed some way to adjust the output of the TEC, I also stuck on a small multiturn 100k trimmer. The leads from the TEC go to the ends of the trimmer. Negative lead to the DMM goes to TEC negative. Positive lead to DMM goes to the trimmer wiper. I then grabbed a red laser and measured it at a steady 202mW with my Laserbee LPM. I shone this laser on my sensor, and adjusted the trimmer until I read 20.2mV on my DMM. Testing with various other lasers shows that this seems to work as reliably as my analog version. I haven't had it long enough to see how it does over time, but so far it looks quite promising. I checked a 2W handheld on my Coherent 210 and read 1.8W. On the DMM, I read 185.9mV or 1.859W so pretty close even at a higher power and IR.
Some pictures ...
The TECs used :
The DMM and DMM to LPM Adapter :
A closer shot of the sensor :
With the DMM on and ready to measure :
Taking a measurement (232mW) :
This is another fairly simple way to measure laser power. The drawback, is of course the need to set it up either with another LPM, or a laser of known power. A DMM that can output to a PC would be interesting ...
Some pictures ...
The TECs used :
The DMM and DMM to LPM Adapter :
A closer shot of the sensor :
With the DMM on and ready to measure :
Taking a measurement (232mW) :
This is another fairly simple way to measure laser power. The drawback, is of course the need to set it up either with another LPM, or a laser of known power. A DMM that can output to a PC would be interesting ...