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| How to check a 230VAC sine/modified wave with an oscilloscope (FNIRISI 1013D) |
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| joeqsmith:
--- Quote from: juan3211 on March 22, 2023, 03:13:58 am ---..They are quite complicated for me, but this is my fault, not yours. I am newbie. I can see that you measure the wave form after a transformer with little distortion in it. As I understand, in this videos you are not comparing the wave before and after the transformer, are you? I have tried to searched a video with this comparation but I can not find anything similar. .. --- End quote --- Unlike you, I provided a plethora of information about my goals. I mentioned what I showed was just for fun. I based my criteria from IEC 6100-3-2 which calls for 40 harmonics. Living in the USA, I used a fundamental of 60Hz, or 2400Hz for the upper end. To improve my scope's limited vertical resolution, I set the sample rate (after filtering and decimation), of 3X over the 40th harmonic (7200Hz). I stated that ANY measurement will have errors and that transformers are not all the same. I've shown using/designing transformers well into the MHz on this forum. I mentioned that I had no idea what that transformer I used for these two videos was. It is very old and possible an audio transformer from a tube amplifiers. To get some idea of how it behaved I swept it from 10Hz to 200KHz and we were not close to the 3dB point. I then overlaid the primary and secondary along with the LEM at 100kHz using basically a resistive load (PF=1). It was far beyond what I needed to meet my goals. You shouldn't expect what ever E core you find to yield the same results. Still if you needed to measure MHz on your AC mains, I made a few videos walking through the calculations for a couple of diff probes I cobbled together. With diff probes being so cheap, it's nothing I would recommend building. |
| Zero999:
I haven't read the entire thread in detail. It's now too long and filled with fluff it's completely unreasonable to expect anyone to read thoroughly. Briefly: yes it's possible to measure the mains with a standard x10 probe, if the neutral is connected to mains earth. Just connect the probe to the phase conductor and it will work. Obviously don't connect the neutral of the grid to earth, as the only the distributor is allowed to do that. In the case of an inverter: check the resistance with a multimeter, when it's connected up, but switched off. It's generally a good idea to earth the neutral of an inverter to prevent it from floating at high voltages. Read the manual. If in doubt, use two x10 probes: one on the live and the other on the neutral and the math/differential function. As mentioned above, a small mains transformer is also a decent option. It won't introduce any noticeable distortion on a pure sine wave, but perhaps a little on the modified sine wave. A toroidal transformer is better. I've found small mains transformers are generally good up to 10kHz, but obviously the losses will be higher with increasing frequency. I'm purely referring to using one for voltage measurement, but to power anything. |
| juan3211:
Thanks a lot for this answer ! --- Quote from: Zero999 on March 22, 2023, 08:53:50 pm ---I haven't read the entire thread in detail. It's now too long and filled with fluff it's completely unreasonable to expect anyone to read thoroughly. Briefly: yes it's possible to measure the mains with a standard x10 probe, if the neutral is connected to mains earth. Just connect the probe to the phase conductor and it will work. Obviously don't connect the neutral of the grid to earth, as the only the distributor is allowed to do that. In the case of an inverter: check the resistance with a multimeter, when it's connected up, but switched off. It's generally a good idea to earth the neutral of an inverter to prevent it from floating at high voltages. Read the manual. If in doubt, use two x10 probes: one on the live and the other on the neutral and the math/differential function. As mentioned above, a small mains transformer is also a decent option. It won't introduce any noticeable distortion on a pure sine wave, but perhaps a little on the modified sine wave. A toroidal transformer is better. I've found small mains transformers are generally good up to 10kHz, but obviously the losses will be higher with increasing frequency. I'm purely referring to using one for voltage measurement, but to power anything. --- End quote --- |
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