LaserBee 3.7W
Yesterday I wrote about my FieldBest optical power meter. Today we’re looking at another of the optical power meters I mentioned in that post, the LaserBee.
The LaserBee is sold by J.Bauer Electronics and comes in a number of versions. The version I have is the LaserBee 3.7W. This is a USB attached instrument with no internal display.
In the previous post I showed how this compared to the other meters I have, but here are the results again for reference:
As mentioned in that post, it seems to underestimate the power of my 1.2W laser, but is more accurate on the low end. I decided to open up the device and take a look inside:
There are a couple of interesting things here, firstly there’s an IC which has had it’s markings removed. I strongly suspect this is a PIC using the adjacent ceramic resonator for its clock. A CH340 is also on the board, which is used to provide a USB serial interface. There are no opamps, which surprises me. Possibly the single transistor is being used as an amplifier for the input from the “thermopile”.
The thermopile appears to be a repurposed TEC/Peltier, painted black so that it adsorbs visible light:
This seems to be a common approach used in homebrew power meters. Thermopiles supplied by Thorlabs and others appear to use a large number of thermocouples in series. This creates a larger total output voltage, using the Seebeck effect. TECs also use the Seebeck effect, but generally use P and N type semiconductors.
I couldn’t find much academic literature on using TECs as temperature sensors. TECs also use the Seebeck-Peltier effect, but the fact that they use P and N type semiconductors suggests to me that the output voltage may be less linear than that from your typical thermocouple.
Perhaps this somewhat explains the difference in power measures between the LaserBee and FieldBest/Newport…
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