A while ago a djozz thread inspired me to get out the screwdriver.
The sensor in many of these looks to be the same photodiode.
Inside my Dr. Meter
I found this as a sensor.
The sensor is hidden under the expected filter. Looks fairly centered on my meter.
It looks awfully familiar…
To the OSRAM BPW34 PIN photodiode.
This is the sensor made famous in Terry Oregon’s sensor thread for use in measuring PWM:
And my build using it based on Terry’s thread:
I have found the OSRAM diode to be linear until the circuit starts to clip on the high end.
Its fast response time (and low price) makes it a good choice for getting a look at the PWM character or driver artifacts without having to try to get a physical connection to the driver circuit.
djozz - a pass-a-round light of known output is a great idea. It will be interesting to see how the various measuring “spheres / tubes / boxes / contraptions” compare.
