OScope help for newbies! Is there a USB model that can handle 125 Volts?

Discussion in 'General Electronics Chat' started by iamjyoung, Feb 19, 2010.

  1. iamjyoung

    Thread Starter New Member

    Feb 19, 2010
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    Hey guys, I am not a gearhead lilke a lot of you guys on this board, but I was hoping someone can help me with ?? that are probably very easy to you.

    I have a hobby of playing with car stereos, I have been helping friends install them. A s I get further and further into it I am learning more and more about power. It is really cool, but at this point I just need a scope that will help me look for clipped signals coming from my amp. From I can tell my needs are VERY basic. But I think since I am dealing with audio syttems putting out 2500 watts to subwoofers and 500 watts to spekaers, my voltage needs are a bit higher than what I see the USB model supporting. So my questions are:

    I see some USB setups that allow up to 20V input, does that mean 20V max or 200V if I use 10X probes?

    I like the idea of a PC so I can do some really nice screen caps vs video taping a scope.

    Thanks in advance!
     
  2. Mike33

    AAC Fanatic!

    Feb 4, 2005
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    200V if you use 10X probes, which are really a voltage divider that yields a /10 result...so the USB input would only be seeing about 20V if your input was 200V.
    Test that out first, using the 12V car battery to get 1.2V, or you might find you've made some mistake and blow your input!!!!!! You have to connect grounds in common, obviously...

    Another thing to keep in mind is that if you use a simple setup, you might see some odd results due to the capacitance and associated filtering caused by using the probes with a USB scope. But for your purposes, I would expect to get decent, if not 100% "professional", results. I would personally set everything up, and slowly bring the output up, keeping an eye on what's going on (adjusting H and V scales as you go). A prior test with a DMM will also ensure you're not going to spike the USB and kill things!
    Good luck, it's definitely do-able if you keep a logical approach in mind....
     
  3. iamjyoung

    Thread Starter New Member

    Feb 19, 2010
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    I appreciate you taking the time. Asi look at manuals it seems like most USB units will only accept 2 volts and 20 using the 10X probes. I found one that does 5 volts / 50 volts max . . much better but seems like not many folks need to measure voltage higher than 20 volts? At least with lower end USB stuff . . so my last question anyone see a good USB that can handle 10 V / 100 volts max using 10x probe?
     
  4. VoodooMojo

    Active Member

    Nov 28, 2009
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  5. someonesdad

    Senior Member

    Jul 7, 2009
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    You can also use a 100X probe. Here's one place to find them.
     
  6. VoodooMojo

    Active Member

    Nov 28, 2009
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    S.O.D, Thats a decent price.
     
  7. retched

    AAC Fanatic!

    Dec 5, 2009
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    $44! That is very decent. I paid $160 for a set..

    How much do you have budgeted for your O'scope? You may be surprised what you can get these days. The scope I have is $289 delivered. 300v with a 1x probe. It comes with two 10x and usb connectivity. Where do you live? You may want to put your location in your profile. (see the upper right corner of my post) Knowing locations can help with pointing to stores and sites that can get you what you need.

    [ed]
    (I'm not stealing your lines Sgt.Wookie)
    [/ed]
     
    Last edited: Feb 20, 2010
  8. iamjyoung

    Thread Starter New Member

    Feb 19, 2010
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    is the 100X ok to use if my software does not have a 100x setting? I was thinking about this unit:
    The stingray:
    http://www.easysync-ltd.com/

    it is 5v so I guess I could do up to 500 volts with a 100x? Anything I should look out for?

    btw, I am in Austin TX

    thanks again guys for all the help!!!
     
  9. iamjyoung

    Thread Starter New Member

    Feb 19, 2010
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    which unit do you have?
     
  10. retched

    AAC Fanatic!

    Dec 5, 2009
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  11. retched

    AAC Fanatic!

    Dec 5, 2009
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    If you have a problem with your probes while using a usb scope, it will fry the scope and the pcs usb..or more.. BE CAREFUL.

    I just checked out that easysync site.. GET the OWON. $220 plus shipping for a pc based scope.. $60 more dollars and you have one you can take anywhere and dont need a pc for.
     
  12. iamjyoung

    Thread Starter New Member

    Feb 19, 2010
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  13. retched

    AAC Fanatic!

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    You can transfer your scans to your pc through the usb.. so the answer is yes. You can make it "look" many different ways. You can use different o-scope software to display the resulting measurements.
     
  14. someonesdad

    Senior Member

    Jul 7, 2009
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    Everyone's needs are different, but I'd like to mention to the OP that I think I would be unhappy with a USB scope. Certainly, it's better than nothing for e.g. work in the field where you want to travel light. But I would far prefer having a "real" oscilloscope that has the usual knobs, buttons, and display. I have to state I have not used a USB scope, so I have no personal experience -- I might feel differently after having used one. You can read one review on them by Jack Ganssle and I would assume you've searched the web for other reviews.

    From experience, I can tell you that buying an oscilloscope is a bit like buying a metal-working lathe. The newbie gets the lathe installed and thinks he's all ready to go. Then he realizes that he'll be dumping a bunch of money into tooling for the lathe. Experienced home machinists usually say to budget somewhere between 0.5 and 1 times the price of the lathe for tooling. Of course, you can spend far more if you wish.

    You'll want to budget some money for some decent stuff to probe circuits with. I made do for a number of years, but finally one day a few years ago I decided to bite the bullet and spend some money to get some probes. I bought some probes to work with my HP 4 channel 100 MHz digital scope that was made around 1991 (I got the scope used on ebay). Here are the probes I decided to buy:

    1. I got the CT2675A 200 MHz probe (here). I paid $10 extra over the 100 MHz probe to have a probe that would allow me to upgrade later to a faster scope and not have to buy new probes. I like the REF/1X/10X switchability. The 1X position is intended for low-amplitude, low-frequency signals. These are my most-used probes and I would replace them with exactly the same probes if I lost them. With a BNC female to dual banana plug adapter, I also use them with my DMM.

    2. For higher voltages, I got the CT2707 100X probe, as I mentioned in a post above.

    3. The most expensive purchase was a 25 MHz differential amplifier. I occasionally make measurements on AC line stuff and higher DC voltages and I feel such a tool is mandatory for safety. For example, it lets me make measurements of the voltage across a current shunt on the high side of the AC line and do it safely. This gives me greater bandwidth than I'd get with a current clamp or my HP 428B. I honestly don't use it very often, but when it's needed, nothing else works quite as well.

    Yes, purchasing these tools was a pretty big expense. However, I took the long-term view, much as I did when I purchased tooling for my lathe decades ago -- I figured this stuff would be with me for the rest of my life if I took care of it. I still have and use two Phillips 25 MHz probes that came with a scope I bought nearly 35 years ago, so this isn't a bad assumption.

    One piece of advice: find and use a robust storage container for your probes. I keep mine in two metal boxes. One was made for some US government application (I think it came from a Navy ship) and the other is a metal first aid box my son-in-law gave me. I have a B&K 2534 scope on loan and it has a nice storage container in the top of the scope for probes. The container is roughly 2x8x9 inches, which easily holds two probes and a few accessories.

    Finally, I realize that spending $400-$500 on stuff like I did might be out of the range of the average hobbyist. It would be for me too; however, I also use this stuff for occasional consulting work and the revenue paid for the parts. I'd suggest this as a possible route to more equipment to other hobbyists -- but you have to acquire useful skills and figure out how to sell those skills to people who are willing to pay for them.
     
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