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| DIY budget auto test oscilliscope and current clamp |
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| tatel:
Oh man, it seems you have a big empanada between your hears. You'll need to do your homework, can't expect us to do the work for you. But, there are some hints: That FNIRSI oscilloscope+current clamp in the video linked before, will do the work at about half the budget you mentioned in your original post. Since the Owon you mentioned is cheap, I guess most of the money was in the current clamp. I just checked and it seems that clamp could be bought on amazon for less than $30 https://www.amazon.com/HoldPeak-HP-605A-Current-Adapter-Clamp/dp/B07X8HYLHR As said in the video and previous responses, you can use any current clamp that produces a voltage, which is what an oscilloscope measures. Ideally you would look for a current clamp provided with a BNC connector, but banana-to-BNC adapters are a thing if needed. You should look for a quality one, perhaps from digikey and from a reputable brand, because cheaper ones can have bad insulation. But you could get a cheap one to start with. https://www.amazon.com/Binding-Coaxial-Splitter-Connector-Adapter/dp/B07TC1L8RP While Fluke stuff is excellent, I very much doubt you need a Fluke clamp to do what you need. If your engine needs a couple hundreds amperes to crank, no problem if the clamp reads 175, 225 or 100 amperes, what you are looking for is the relation between current peaks (indicating that compression is at his peak) and injector/firing pulses, that is what gives you about how your engine is working. All four cylinders show equal current peaks at the appropriate time relative to firing pulse? Then it's OK. One of the four shows half the peak? Then that cylinder has half the compression. Firing pulse is missing at compression peak? You'll need to check why is that happening. And so on and on. Hantek has a current clamp that produces either 1 mV/A or 10 mV/A, meaning that a 200 A current would be seen in your oscilloscope either as a 200 mV or a 2V signal. It has a BNC connector and costs $75-100: https://www.amazon.com/dp/B09NC6F6NB Please note, I'm not an expert at all, I just use a dirty cheap $40 toyscope to look at my car's sensors. So don't quote me on this matter. I'm just trying to give you some clues, because it seems obvious to me you are at a loss right now. Hoping this will help you. But, if you don't do your homework, nothing will help. |
| daheee:
I've been trying to research this, actually. But given my lack of knowledge, it's difficult for me to know if my thinking is correct. I believe I only need a 60amp clamp. Thought I needed 200. That should handle most of my needs. ScannerDanner uses a 60amp one to measure the flow to the starter for things like a compression test. I appreciate your help, and I agree I don't need expensive stuff for my needs -- but I've done the whole buy cheap buy it twice enough to be wary. I think I have enough information now. Thanks again for your help. |
| ADT123:
--- Quote from: daheee on September 01, 2024, 04:23:13 pm ---I've been trying to research this, actually. But given my lack of knowledge, it's difficult for me to know if my thinking is correct. I believe I only need a 60amp clamp. Thought I needed 200. That should handle most of my needs. ScannerDanner uses a 60amp one to measure the flow to the starter for things like a compression test. I appreciate your help, and I agree I don't need expensive stuff for my needs -- but I've done the whole buy cheap buy it twice enough to be wary. I think I have enough information now. Thanks again for your help. --- End quote --- I would be surprised if he used a 60A clamp - compression test often needs >200A Perhaps he was using a 600A clamp? See https://www.picoauto.com/library/automotive-guided-tests/petrol for some example waveforms |
| daheee:
low amp probe (60 amp) compression testing by scannerdanner I may purchase the uscope. Still thinking about it, provided the low amp probe that comes with the master kit can do what scannerdanner did in the video. |
| ADT123:
--- Quote from: daheee on September 01, 2024, 10:51:37 pm --- low amp probe (60 amp) compression testing by scannerdanner I may purchase the uscope. Still thinking about it, provided the low amp probe that comes with the master kit can do what scannerdanner did in the video. --- End quote --- The current measured was off the screen at the start then >120A. It worked OK with that specific current clamp but best not to plan to use a clamp at 2x or more of its rated range. High compression engines will be higher currents still. Not trying to sell you anything but for compression you need a "high amps" clamp |
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