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Thread: question about usb osciloscope

  1. #21
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    well thanks for the compliment but I'm not any kind of an electronics person...I just tinker and have fun and with this project I just had a concept and some space requirements and played the rest by ear and somethings didn't tie together in the end as well as if I had a plan but anyway it's working pretty good I think.

    Is it the accuracy of the clamp meter you don't like? Really not sure I have room for shunts...depends on how many I need to cover the amps without losing accuracy in the bigger shunts I think?

    BTW I've checked the clamp meter against the more accurate shunt meter in a DMM and the clamp meter matched good except at less than a few amps.

  2. #22
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    The thing i dont like with the clamp meter is the whole process of taking the reading. Is a little messy. On the other hand using a shunt is more straight forward and you can also forward the readings to a PC, logger, etc.

    As for the number of the shunts you need, it depends on the 12V rails you have. If you have two (suitable for most of the today PSUs) then with 4 shunts you are ok (12V1, 12V2, 5V, 3.3V). The 5VSB and -12V can be measured directly with a DMM since they are under 10Amps (nearly all DMMs can measure up to 10Amps).

  3. #23
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    ah well it takes me just a few minutes to double check amps and then measure and write down all 5 voltage outputs plus fan voltage, int and exh. temps, VA, PF and AC watts and uhh fan RPM I am doing now too and then a couple more minutes to set up the next load and check amps...so it's less than 10 minutes "work" for all the measurements and then wait like 30 minutes or more for temps and fan voltage to stabilize under the new load and repeat.

    Regarding rails I really don't pay any attention to the number of rails the test unit has except for current limit concerns and I don't measure 12V voltage on a loaded connector. I have 6 PCIe connectors, an 8-pin CPU, 4-pin CPU and 24-pin straight connected to 12V loads and can measure current thru any of them alone (or either side of 8-pin) or any combination of them at once so it'd take 10 shunts to duplicate that plus one each for the 3.3V and 5V and yeah I don't measure amps on the -12V and 5vsb. I checked the loads there when I put it together and just use what the switches give which is within .1A....I calibrated the amps at the factory like a Sunmoon

    I dunno...there's a lot of ways to do it and I'd do some things differently if I did it again and have changed some already of course...think i want a digital line voltage thermostat for the heater next....or a variac lol

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    I finally finished the program that gets the readings from the labjack. Now I can monitor every detail of the test PSU and log it too. The numbers bellow are from a random number generator that I have included in the program for debugging purposes. The red fonts indicate that a reading is out of specification and the green that it is normal. In the logging section when there is a "*" before the time it means that there are readings out of range. The readings can be automatically transferred to Excel.






  5. #25
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    Cool, what's the data acquisition equipment?
    It's been a hard day's night and I've been working like a dog.

  6. #26
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    That's working good...can you adjust the polling rate?

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    Quote Originally Posted by Travis View Post
    Cool, what's the data acquisition equipment?
    Its a LabJack U3-HV

    http://www.audon.co.uk/u3.html

  8. #28
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    Quote Originally Posted by Makalu View Post
    That's working good...can you adjust the polling rate?
    Yes. Currently is set to only 2 samples per second (for each V, Amp measurement). I can easily up it to several thousands per second but then the log files will be enormus!

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    lol yeah I have some huge files from logging volts and temps even at that .5s polling rate...superfast might come in handy for a little while at times though.

  10. #30
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    Yesterday my stingray arrived



    and a photo of the LabJack


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