A conversation with Don was running away in another thread, so I’m hoping to restart it here.
The assertion is that being able to measure laser power (and especially power loss at a mirror or lens) is extremely useful when optimising a laser cutter. But they’re expensive, and the common ones are rather low power - intended for optical fibre measurements.
Here’s a description of how to use one, and a possible cheap option :
Russ suggests this can cost a few hundred dollars, though there are a couple on ebay at present for £100-£150.
I think Russ’s solution is pretty decent - I think he charges £30 and it comes with a (probably generic) calibration.
However, all you really need is a lump of black metal and a temperature sensor.
How about a small black-anodised heatsink, an electronic temperature sensor (DS1820 or something similar with higher resolution) and an arduino ?
Fitting a resistor to the heatsink would allow self-calibration : it could be used to heat the device at a known rate which would then model the same objects response to laser heating. A second temperature sensor (not attached to the heatsink) could measure ambient for the necessary correction.
Better than measuring the temperature of the block when it reaches equilibrium would be to measure the rate of heat rise. This would then give a real-time measurement of power until the block got too hot to be useable.
Another possibility would be to operate it like a bridge circuit : have two similar heatsinks, separated so that they’re in a similar environment but one doesn’t heat the other. Heat one with a resistor, and the other with the laser. Control the resistor power such that both objects are the same temperature, and the DC power will equal the optical power. This is the thermal equivalent of instruments like a grease-spot photometer.
