Quote:
Originally Posted by RobF
Karl, if the problem with floating supplies is lack of a common earth (possibly), what's the downside with non-floating if I may ask?
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One of the functions of DC power supply (beside giving you steady (regulated) DC voltage) is to provide isolation from mains supply. By connecting the mains Earth to the common or negative terminal of the PS you broke that insulation and your PS is (under some circumstanced) electrically connected to the mains.
Look at it this way. Some people build really good piers with deep concrete base. The pier itself may have a similar or even better Earth resistance then your house wiring Earth. Now what will happen if some appliance in the house has leakage or short circuit? The fault current will go along your house mains wiring to the Earth point in your switchboard and blow the fuse or trip the circuit breaker on offending circuit. But, some part of that fault current will also (and it can be significant part - depending on ratio of the Earth resistance on your switchboard and the pier Earth resistance) will pass thru your wiring to the pier and the Earth somewhere on power pole in your street.. As the fault current passes thru your common terminal of your PS it changes ground reference for the voltage regulator and the possible outcome is blown up CCD camera.
All of this is much more complicated then what I have written. I just want to make it reasonably easy to understand to the people with no electronics./ electrical background.
To put it in nutshell. Best option to power Astronomy gear is a battery. Second best are floating PS – analogue PS is well ahead in terms of clean DC, but way behind in terms of costs, efficiency and weight. Switchmode PS are cheap and very efficient but not as clean as analogue. I would not use non floating PS on my Astro gear.