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Parallax USB Oscilloscope Question — Parallax Forums

Parallax USB Oscilloscope Question

Andy4usAndy4us Posts: 5
edited 2005-10-08 15:33 in General Discussion
I'm considering buying one to help me with my home projects. Apart form the normal 0->5V stuff, I will also need to measure both RS232 and RS485 levels. Will I be able to do this either with the product as it ships, or will I need different probes. Are different probes available, the connector doesn't seem to be a BNC.

thanks,

Andy

Comments

  • NewzedNewzed Posts: 2,503
    edited 2005-10-03 16:54
    I believe the scope will handle 0-40 volts as shipped.· The scope comes with a probe for Channel a, Channel B and an external trigger probe.

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    Sid Weaver
    Do you have a Stamp Tester yet?
    http://hometown.aol.com/newzed/index.html

    ·
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-10-03 17:00
    Hello,

    ·· The USB Scope will handle 20V P-P from negative to positive side of the signal.· This boils down to a max 10V DC input down to -10V.· To go any higher you will need to build a divider.· Standard scope probes don't connect since our scope uses a barrel plug on the end instead of a BNC connector.

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • NewzedNewzed Posts: 2,503
    edited 2005-10-03 17:30
    Chris, I can't find my Optascope Manual, so please correct me if I'm wrong.

    As I recall, the O'scope will measure 40 volts P-P.· There is no reference to frequency.· So why would the scope not measure -20 to +20 DC.
    40 volts P-P is 28.28 RMS and the average voltage would be 0.· I have read +12VDC on my O'scope with no problem.

    Sid
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-10-03 17:36
    Sid,

    ·· Can you post a screenshot of your scope reading 12V?

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-10-03 17:40
    Dave and I both connected our USB scopes and ramped the voltage form 0 - 12V.· The scope stops rising at 10V, as it was designed to do.· This is going straight in without any input buffer/divider.

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • NewzedNewzed Posts: 2,503
    edited 2005-10-03 17:42
    Negative, Chris.· The O'scope is connected to my workbendh computer, which does not have Screen Shot and is not even on-line.· Besides, I wouldn't try it again since you say the limit is 10VDC.· That was last year when I measured 12VDC.· how do you arrive at 10VDC max?

    Sid
  • NewzedNewzed Posts: 2,503
    edited 2005-10-03 17:44
    Is the Optascope exactly the same as the USB scope?
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-10-03 18:06
    Yes Sid, they are the same.· In reference to ground the Scope will read -10V through +10V (20V P-P).· You can put 12V into it, as we did, but the display will stop at the second grid line when Volts/Div = 5V.

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • DannyDanny Posts: 56
    edited 2005-10-03 18:53
    On this same thread, I bought an Optascope 81M before you started carrying it, have there been any software upgrades?
    And will they work on a unit that old?
    SN is OP81M1005020381 in case it's needed.
    Thanks!

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    "Never create anything you can't control"
    "The amount of intelligence on the planet is fixed... the population is growing"
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-10-03 19:06
    Danny,

    ·· The current version of the USB Scope software on our website should work fine with your scope.

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • NewzedNewzed Posts: 2,503
    edited 2005-10-03 19:20
    Danny, if you download and install the USB software for your Optascope, please let me know how it runs.· Any improvements?· I'm curious to fond out before I download it.

    Sid
  • Andy4usAndy4us Posts: 5
    edited 2005-10-03 19:22
    Thanks all. How is the overvoltage protection ? If I run rs232 into it, which may be +-5V to around +-15V will I damage anything ? Also Chris, you seemed to insinuate that it will clamp any over range voltages rather than either ignore them. Basically what I'm asking is, if my rs232 is running +-15V will I still get a decent set of signal pulses to read which won't have the correct max/min voltages, +- 10V instead of +-15V, but will correctly indicate the bits. I'm interested in the data, rather than height of the peaks.

    thanks,

    Andy
  • Andy4usAndy4us Posts: 5
    edited 2005-10-03 19:51
    OH, I forgot another question. Anyone had any luck running the software under LInux, or are any plans to make a Linux version
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-10-03 23:37
    Andy,

    ·· No linux version plans...I will see if I can get the engineer who designed the scope to answer your other questions tomorrow.

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • Andy4usAndy4us Posts: 5
    edited 2005-10-08 14:06
    OK, so I bought one, and it's almost paid for itself so far, certainly helped me find a couple of problems. I do have some suggestions though.

    1- A resizeable main window, ultimately so that I could see the whole waveform
    2 - seperate controls for each channel
    3- A (much) longer waveform history. It would be nice be at a fine horizontal scale, but be able to go back several seconds in time. This goes hand in hand with #4
    4 - once stopped, be able to change the horizontal range. The problem is capture the whole signal I have to be a quite a course horizontal range, but then it's much harder to decipher the bits. Zoom does not quite cut it.
    5 When zoomed a grid, based on the horizonatal range and zoon factor.
    6 A cursor control in the horizintal direction that is "click" based. That is one click moves X amount of time based on current horizontal division. Makes "Snap to Plot" much more useful.

    To give you an idea of what I'm doing, I've been tracing issues related to I2c on my board. The oscilloscope works great for signal tracing and confirming that there is a signal, I set the trigger points and capture the I2c coms. I can see that I have data. To capture the packet though requires a course horizontal range. What I am now trying to do is read the data to make sure I'm sending what I think I am. That is proving much harder than it should.

    It seems that the designers of the software really targeted lower end machines, which is great, but I have a P4 with lots of ram and a huge screen, it would be nice to able to use it if I have it [noparse]:)[/noparse]

    thanks,

    Andy
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-10-08 15:33
    Andy,

    ·· I will certinaly pass your information along to the engineer who designed the scope.· In the meantime I think you just found some reasons why our scope is more affordable and not closer to $300 or $400!· =)· As for the signal verification, it almost seems like you would be better of adding a BASIC Stamp Logic Analyzer to your tools collection.

    ·· The BASIC Stamp Logic Analyzer can not only capture several million samples of your I2C data, but it can even decode the data to show you what is being sent.· Please see our examples in the AppNotes on the product page for the BSLA.· I find the BSLA to be an invaluable tool to work with the Scope.· I find I use both quite frequently.

    http://www.parallax.com/detail.asp?product_id=30010

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
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