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Forum Index : Electronics : using a Oscilloscope to view PMA output??
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| govertical Guru  Joined: 11/12/2008 Location: United StatesPosts: 383 |
Hi, the new used oscilloscope arrived. It displays the calibration wave form on each channel. What connections are needed to view the AC output of the PMA? Until now, I have been using a 12 volt test light and multi-meter to test a 3 phase star PMA. Any help will be greatly appreciated. 
just because your a GURU or forum administer does not mean your always correct :) |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Hi Gov It looks like a dual trace, handy. When testing the output of a 3 phase alternator, you need to be carefull how you connect the earth clip of the test probes. If there is a voltage difference between the earth clips of both probes, you could damage the cro. The earth clips are connected internally ( unless its got a fancy floating input amp, not common ), so you only need to connect ONE of the earth clips to whatever you are testing. If you have access to the star connection, you can connect the earth clip to that and the probes to two of the phase outputs, and then see the two sine waves on the screen, out of phase with eachother. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| govertical Guru Joined: 11/12/2008 Location: United StatesPosts: 383 |
Hi, thank you for the help. Spinning the PMA by hand I am to confirm that the PMA does produce a sine wave output. just because your a GURU or forum administer does not mean your always correct :) |
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| larny Guru Joined: 31/10/2011 Location: AustraliaPosts: 346 |
If you can't access the star point, you could create a star point with 3 resistors. Connect the gnd of the cro to the star point of the resistors. For 12 Volt, three 1000 Ohm 1/2 Watt resistors would be safe since the power dissipation would be 12 * 12/1000 = 0.144 Watt. |
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| govertical Guru Joined: 11/12/2008 Location: United StatesPosts: 383 |
Hi, thank you for the help. I am working on a buck converter and the bench power supply I am using is programmable. It was configured with the plus terminal referenced to chassis ground. After I reconfigured the power supply so the negative terminal is referenced to chassis ground all the problems I was having has been resolved. Thanks again. just because your a GURU or forum administer does not mean your always correct :) |
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