Laser intensity drop

[ajfedorec]

Hi,

In one of my chambers I am seeing the raw OD measurement drop massively after around 10 sequential measurements 1 second apart (from ~12000 down to ~50 for a water blank). After 30 seconds without performing a measurement, I get a normal reading again. If I’m running with a culture at 37C, with the OD measurements 1 minute apart, I see a similar drop but no return to normal readings.

From visual inspection it looks like the laser intensity is dropping rather than it being a problem with the photo detector. I can’t see any obvious issues on the board. I am assuming this is the laser over-heating. Would that result in an intensity drop? Is there anything I can do to fix the unit myself or does it need to be returned?

Thanks for any help

Alex

[harrison]

Interesting – I have never seen this before and I have characterised some of them with measurments every second for ~days.
I don’t think the problem is overheating – unless there is some fault in the electronics – since the lasers are dissapating fairly low power so shouldn’t heat up very much. Have you tried doing it with the intensity set to a lower value and see what happens?

Off the top of my head I imagine the most likely scenario is there is a fault the laser diode – they are fairly cheap mass-produced items, probably with far more variability than anything else in the circuitry. In that case asking for a replacement is probably your best bet – unless you fancy soldering in a new laser diode (assuming that is indeed the problem).

[Author]

Posts