Products > Test Equipment
Looking for portable oscilloscope
csuhi17:
Wouldn't any oscilloscope and differential probe solve his problem?
Fungus:
--- Quote from: abgx1 on December 10, 2023, 12:29:58 pm ---But, what if I buy a scope operated from main voltage? In that case, the ground point will always be connected to the ground in the outlet. So, the worst-case scenario is a short circuit between the scope ground and mains voltage, which is not ideal but much safer than the risk of being electrocuted.
--- End quote ---
Any 'scope can be grounded. The Rigol DHO800 has a grounding connector and comes with a big green/yellow wire in the box.
Me? I say "safety" is as much about procedure as the hardware. You can kill yourself just as dead with a $4000 Fluke as with a cheapo Chinese meter.
a) Wear gloves (and eye/hearing protection for very high power circuits)
b) Don't trust your life to the color of wires. Make sure you know which is the live wire and whether the neutral wire is grounded or not. You need a low-Z multimeter for this. I'd get a Fluke 113 if my job was based around "mains AC" (for it's price, high CAT rating and sheer idiot-proofness).
c) Don't do it alone, have somebody else around whenever possible.
d) ...now you're ready to start the test procedure.
--- Quote from: adam4521 on December 10, 2023, 11:37:59 am ---Middle of nowhere, wells, water, 400V, inverter, it’s like a cacophony of jangling alarm bells.
--- End quote ---
It sorta depends on the power of the inverter. A properly-fused 5A inverter isn't as scary as a 1kA inverter...
abgx1:
Well, at some point, the amperage of the fuse doesn't matter anymore because it just won't trip, no matter how hard you're trying. 🙂 The frequency inverters I commonly come across are in the range of 0.18-11 kW, which means around 25-26A at max.
Anyway, I did some studying, and I see four options:
1. Buying differential probes - That's too expensive, at least for now.
2. Buying a scope with isolated inputs - That's even more expensive.
3. Using a grounding connector with a big green/yellow wire connected to the 100% safe grounding point (for example, a lightning rod on those wells) as a reference point so I do not have to use the probe grounding lead at all - That sounds pretty safe to me.
4. Could I use the second channel as a reference point? I mean, I would connect channel 1 through a 1:100 probe on mains voltage. Then I would connect channel 2 through a 1:100 probe to the ground. Finally, I would subtract channel 2 from channel 1.
Now, when I see it written, I think that option 4 is impossible since I will not be able to measure any voltage on channel 1 without grounding. Is that true?
Currently, I am leaning toward the Rigol DHO804 and option (if option 4 is not possible), if you guys do not have a better idea that does not cost a four-figure price. I have excluded Owon from selection since it doesn't have a grounding point other than one on the probe..
Fungus:
--- Quote from: abgx1 on December 11, 2023, 04:33:55 pm ---4. Could I use the second channel as a reference point? I mean, I would connect channel 1 through a 1:100 probe on mains voltage. Then I would connect channel 2 through a 1:100 probe to the ground. Finally, I would subtract channel 2 from channel 1.
Now, when I see it written, I think that option 4 is impossible since I will not be able to measure any voltage on channel 1 without grounding. Is that true?
Currently, I am leaning toward the Rigol DHO804 and option (if option 4 is not possible), if you guys do not have a better idea that does not cost a four-figure price. I have excluded Owon from selection since it doesn't have a grounding point other than one on the probe..
--- End quote ---
No need.
The DHO800 comes with a big yellow/green ground wire in the box. You can ground the scope then just probe the mains with a single probe on channel 1.
shapirus:
--- Quote from: abgx1 on December 11, 2023, 04:33:55 pm ---4. Could I use the second channel as a reference point? I mean, I would connect channel 1 through a 1:100 probe on mains voltage. Then I would connect channel 2 through a 1:100 probe to the ground. Finally, I would subtract channel 2 from channel 1.
Now, when I see it written, I think that option 4 is impossible since I will not be able to measure any voltage on channel 1 without grounding. Is that true?
--- End quote ---
If we consider it from the purely mathematical point of view, since one channel's value is subtracted from another, and they both have the same reference point, the referent point cancels out and does not matter anymore, meaning the probe ground clips aren't even required in this case.
Practical implementation is a different story. I can't confirm that it works, but something tells me that it should be viable.
p.s. you can still touch the exposed ground metal parts on the probes, if they have them. That requires extra care.
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