HI all,
My father runs a clinical lab (blood tests etc) and one of the autoanalizers halts due to random failures in optical sensors (not the same sensor every time). We've checked everything we could, test the sensors, calibrate, and everything is fine. But having a failure in random sensors once a week seems that the issue is not the sensors but something wider like the power supply.
It has been suggested by the technician that there might be a power quality issue. This is the setup
MAINS (it think its 3-phase) -> big UPS (5-10 KVA) -> machine (COBAS 8000 Modular analytics
http://www.cobas.com/home/product/clinical-and-immunochemistry-testing/cobas-8000-modular-analyzer-series.html). To get an idea of what it looks like, have a look at the attached image
NOTE: The UPS is running under 80-90 percent load
Following his advice, id like to have a look at the UPS inverter output and see how the output sine wave looks like.
My test equipment:
Rigol 1054z
I've read quite a lot about how to probe mains with the scope, and im confused.
Solution 1: Use a stepdown transformer: Im worried that this solution might modify the sine wave and smooth out the signal, hiding the real problem.
Solution 2: Connect two probes (one to neutral) and one to hot wire, then use differential to see the wave.
Solution 3: Unground the scope, use only one channel (Idont want to do this).
Any hints suggestions are very welcome. Im a student in EE in my third year and I honestly have no idea how to do this. Ive already watched Dave's video about not-blowing the scope, but I still dotn know how to perform this job
Thanks for your help.
Gaspar