On Wed, 2011-03-16 at 07:23 +0100, Peter Blodow wrote: > Hello Kirk, > I don't see why you should not be able to measure your mains phases with > an ordinary oscilloscope, set up as usual. At least in this country, the > three phases of mains current are ground referenced, 230 V effective > voltage to neutral. Between the phases, as can be figured with a > triangle formula or by trigonometry, there are 400 V eff. (not ground > referenced, of course). Connect each phase with a high resistance probe > or, if exact magnitude is not important, with a small capacitor. It's > just measuring a ground referenced voltage, a little higher than usual, > but still. No floating oscar, as long as you don't want to measure > differentially between phases.
My converter phases are not ground referenced, so I need differential scope measurements or isolated inputs of some sort. > E.g., right now, I am working on an induction heater which outputs 28 > kHz at 800 V maximum, 500 V eff. No problem with my 40 year old oscar. > Since this voltage is ground referenced, I can hook it up to the oscar > input with the ordinary 10 MOhm probe, 1:10. I leave the probe's ground > crocodile off to avoid cross ground currents through the oscar. I only > have to watch the way the plug is connected to the wall outlet to make > sure the leg I am measuring at isn't the grounded one :-) Induction heating is another thing on my to-do-someday list: http://wiki.linuxcnc.org/cgi-bin/emcinfo.pl?Videos Also, I have an ultrasonic cleaner to fix. > Since you have only a 2-channel oscar, connect one phase permanently to > one input for triggering and switch the other beam between the two other > phases. This will show you their phase difference. That's the plan. > > Best spring greetings > > Peter Blodow The problem with Spring is all the gardening that won't wait. I should have started my seedlings by now. -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/index.html California, USA ------------------------------------------------------------------------------ Colocation vs. Managed Hosting A question and answer guide to determining the best fit for your organization - today and in the future. http://p.sf.net/sfu/internap-sfd2d _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
