Viability of cheap laser power meter

[reportingsjr]

Does anyone know how well these cheap laser power meters work? http://www.amazon.com/dp/B00EOMTSOO

I have a 60W CO2 laser engraver and want to see how much my tube has degraded as well as using it for alignment. These types are much cheaper than digital ones, but seem a bit sketchy.

Thoughts?

[Fraser]

I have digital laser power meters for CD player repair but you are working with far higher power which makes the item you detailed viable. From what I can see, it is a mechanical thermometer with a laser light absorber attached to the tip. It is responding to the heating effect of the laser. It should work, but how accurate it is I have no idea. These types of thermometer are commonly found in kitchens for checking meat core temperature 

RF power meters from Marconi used to have a thermistor or thermocouple based temperature monitoring circuit that responded to the heating effect of the RF energy on the termination. It is much the same idea as the laser power meter your detailed in terms of the principle used.

Aurora

[kripton2035]

one customer from the 200w version seems to be happy with it
apart from that...

[ajb]

Clever little meter.  Since the reading is based on the temperature of the block as heated by the absorption of the laser, the accuracy will be affected by ambient temperature, airflow around the detector, and mounting method.  You'll want to be sure there isn't a lot of air moving around the detector (which will artificially cool it), that you note the reading on the meter before you start and deduct the 'cold' reading from hot reading, and you'll want to mount or hold it close to the dial rather than the detector (which would artificially cool or heat it, depending on if you have it in, say, a metal bracket, or held in your hand).  The digital thermopile based sensors actually have the same sensitivities in principle, but are typically constructed to better reject those influences, and it's easier to zero out initial offsets based on ambient temp.  The one you linked is probably okay for what you're looking to do, although the response time will likely be pretty slow which may make using it for alignment tricky. I wouldn't necessarily trust if for precise absolute measurements, but you should certainly be able to do a decent relative measurement with it.

If you wind up getting one, I'd be happy to do a side-by-side with a Coherent Powermax LM-20, although all the sources I have to compare with at the moment are visible (450-650nm) and <10W CW, so they may not give an accurate picture of accuracy with IR at ~60W.  Just drop me a PM if you want to arrange it.