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Using an old Newport USB power meter, checking calibration


New member
Oct 6, 2011
I picked up an old Newport 841-P-USB with a 818P-110-19 thermopile head. Newport don't seem to supply software for this unit any more (the legacy software doesn't work). But I can communicate with it over serial.

I'm now trying to figure out how out of calibration it is. It was last calibrated in 2008.

A cheap 532nm 301 laser from eBay reads as 30mW.
A slightly more expensive 532nm eBay "100mW" module (ebay item 142313746605 ) reads as 75mW.
My Alcon 532nm laser (which should be low single digit Watts) reads as 1.7W.

So it seems to work, but I'd like to get a bit more confidence in the readings. Are there any easily available power standards which would give be accuracy to ~10mW? Overall, I don't amazing accuracy. But I'd like to be confident that my measurements (mostly at 532nm) are accurate to ~50mW in the 50mW to 1W range.