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Multimeter purchase help needed

Discussion in 'General Electronics Discussion' started by scieqp, Aug 8, 2012.

  1. scieqp

    scieqp

    12
    0
    Aug 8, 2012
    Hi all,

    I am looking for a multimeter or cheaper DAQ that can do the following:

    1. Can record data continuously for at least 7 days
    2. Must be able to do 3 readings per second minimum.
    3. Input impedence at 10 million ohms at -10K mV ~ +10K mV, preferrable a unit that can do 10 giga ohms such as the NI 6210 would be great without the price tag of the NI DAQ unit.
    4. USB to USB only. No RS 232, I do not have a serial port, and serial to usb cables do not work on my machine very well, I want usb to usb.
    5. The data must be continually able to download to the pc by itself if possible. And the file be emailed to another.

    I have seen some units that can do 10 million ohms at a resonable price, like I think $40, but they use RS232. And honestly I am hoping to find something that can do 10 giga ohms.

    I saw a thread here. https://www.electronicspoint.com/re-freaky-amazing-dmm-t151939.html they claim it can do 14giga ohms at 400mV. I am assuming they ment with a unit of K??

    Any suggestions let me know. I am willing to spend around $100 or so for a multimeter. But I am not willing to spend $600 on an NI device. If there is another manufacturer as reputable as NI with a lower price I would consider.

    Thanks in advance!
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,174
    2,690
    Jan 21, 2010
    Sounds like you want Champagne on a beer budget.

    3 readings per second for 7 days either means a lot of internal memory (2 million samples) or external logging to a PC.

    Having it run continuously for 7 days may be a stretch for some multimeters which could be close to running through a battery in around this time or less.

    Even cheap meters these days have optocoupled USB interfaces, so getting the data shouldn't be a problem, just don't expect the multimeter to email it!
     
  3. CocaCola

    CocaCola

    3,635
    4
    Apr 7, 2012
    If I was doing it I would setup the logging PC as an FTP, and drop the logs in the FTP directory and have the other computer download from there when needed... Even HTTP will work...

    There are also remote file transfer clients that will allow you to save to remotely connected computers as well... All my remotely located websites are mapped as local drives on my development computer, I can save and move files as if they are local (speed is of course slower)...
     
  4. scieqp

    scieqp

    12
    0
    Aug 8, 2012
    Ok guys, a little confusion. I don't expect it to email or upload the data as it reads it, it might be a nice function in the future, but it's not necessary. It would be nice for the unit to be hooked up via usb and just download the data to the pc as it gets it and stores it in a file.When I am ready to stop it, I can find that file and then email it myself.

    I don't think it has to cost an arm and a leg for this, I have a weather station that cost me around $120 that will upload my data to weather underground every minute, this is software related, not hardware. So I don't think it would be all that difficult to do provided that the software is available to do that.

    Question still remains though, any recommendations for a unit that fits the requiements above?
     
  5. CocaCola

    CocaCola

    3,635
    4
    Apr 7, 2012
    Is it taking 3 readings a second and logging them, and emailing them? Comparing an over the counter mass produced item to one custom configured to your needs is apples to oranges, and pennies to dollars...
     
  6. scieqp

    scieqp

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    0
    Aug 8, 2012
    The weather station uploads my data to three different websites every minute JFYI.

    The multimeter is what has to sample 3 times every second. You guys are focusing on something that I said I do not necesiarily need at the moment. I am more interested in knowing your opinions on what unit I should buy then focusing on this uploading issue. I can take the file every day and email it myself, that is no big deal. I am more interested in knowing what units can meet my other needs. thank you.
     
  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,174
    2,690
    Jan 21, 2010
    To be fair, we're looking at what you stated your requirements were and compared them with what our experience tells us is available.

    How about this.
     
  8. scieqp

    scieqp

    12
    0
    Aug 8, 2012
    Perhaps I am not stating the requirements correctly or people are reading to much into what I need. Actually if one looks closely at my requirements about the email portion it says: "And the file be emailed to another." meaning I will email the file myself once the data has been downloaded.

    The meter you sent me looks nice, but perhaps I am not understanding the spec list. It does not appear it can do -10K mV. And the specs look incomplete. I do not see any impedence values.

    It is absoluetely necessary that the unit do the following:

    1. Can record data continuously for about 24 hours to 48 hours, 7 days is optimal.
    2. Must be able to do 3 readings per second.
    3. Input impedence at 10 million ohms at -10K mV ~ +10K mV.
    4. USB to USB connection so that the data can be downloaded continually. I hope this part is automatic, the downloading of the data does not have to be 3 times a second, it can store it locally for a minute or two and then download the values, but the readings need to be 3 per second and shown.

    I hope this is clearer.
     
  9. GreenGiant

    GreenGiant

    830
    5
    Feb 9, 2012
    input impedance is 90% of the time at or above 10Mohms in meters like this

    Also what do you mean when you say "-10K mV ~ +10K mV" do you mean 10,000V, 10V (10,000mV), or 10mV?

    also looking at the instructions download yields this...

    and

    assuming rage is supposed to be rate
     
  10. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,174
    2,690
    Jan 21, 2010
    No, I have one of these and it gets very angry at the world three times every second. :D

    I actually do have one of them. I was after another (cheap) multimeter and I got this one because for the few bucks more it could do data logging. I haven't had the need to try it out, but maybe I will on the weekend to assist the OP.
     
  11. scieqp

    scieqp

    12
    0
    Aug 8, 2012
    Thanks for all the replies.

    10K mV = 10 V. The signals we need to measure range from minus 10K mV to positive 10K mV, thus the meter needs to be able to show and record these ranges. The NI 6210 and NI 6212 can do that, but those units are very high priced, but they can also measure 10G Ohms. This would be nice to find in a multimeter, but it seems like it doesn't exist.

    I could not find more specs from the website to download, I was only looking at that page also, if there was a download section I wasn't looking for it, thus didn't find it.

    Did I say rage? LOL I can't see where I wrote that, but yes it is range, not rage. ha We need it to detect, record and show at least 3x times a second as written before, thanks.
     
  12. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,174
    2,690
    Jan 21, 2010
    "Rage" is on the specs for a meter.

    So you want to measure, 3 times per second, voltages in the -10V to 10V range. And you are happy with some connection to a PC or whatever to gather these readings?

    Yes?

    Do you have a requirement for input impedance?

    Do you have a requirement for accuracy and/or resolution?

    Don't use pairs of multipliers (like 10k mV because it's confusing)

    Oh, and you want it to cost less than 0.1% of a G c-cent? (Oh dear, did I just do what you did?)
     
  13. GreenGiant

    GreenGiant

    830
    5
    Feb 9, 2012
    The last 2 quotes that I posted are from the document that is located here where it appears to fit all of your specs, 10Mohm impedance at all voltage readings other than 400mV range, it can only measure to 40Mohms unfortunately, but it reads and logs at 3S/sec

    the specs are from the document I have linked above, which on the site for that multimeter its the "instructions" link on the right hand side underneath product information.

    rage was from the document in place of rate, not from you.
     
  14. scieqp

    scieqp

    12
    0
    Aug 8, 2012
    yes, three times per second. -10V to 10V range yes. pc connection via usb , yes.

    of course the meter can have additional things or have a bigger range, but this is the minimum requirement.

    input impedance must be at least 10M ohms, but would prefer something much better. But I think this is what increases the price of these units, but I am not sure. I just know the NI 6210 would actually be quite perfect for our measurement, but it's out of our budget.
    Resolution I think doesn't matter, are you talking about the resolution of the graph that is created? That is downloaded so mustly depends on the software no? I'm not an expert here, so... Provided I can read it, it should be fine. Accuracy, well, it should be accurate enough to get reliable data, I know this is very vague, but.. let's not make the accuracy so bad that the data is useless.
     
  15. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,174
    2,690
    Jan 21, 2010
    Resolution means how many digits. i.e. do you need to resolve to millivolts, or is tens of millivolts OK.

    I tried that meter and it looks to me that it only does about 1 reading per second.

    I was out today sand looked at a couple of logging multimeters. None of them seem to do more than 1 reading per second.
     
  16. scieqp

    scieqp

    12
    0
    Aug 8, 2012
    Need to resolve to milivolts. We need at least four digits.
     
  17. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,174
    2,690
    Jan 21, 2010
    4 digits, so 0 to 9999 millivolts? (and 0 to -9999)

    This pretty much means you need a 4 1/2 digit meter

    You realise the accuracy will probably be +/- 3 in the last digit (or worse) unless you pay big(ger) bucks.

    I'm pretty much stuck on the 3 samples per second. I can't find anything affordable that will do that.
     
  18. scieqp

    scieqp

    12
    0
    Aug 8, 2012
    Well. Four whole numbers will be enough. 0 to 9999 and 0 to -9999 yes.
    Yep, the accuracy issue should be ok.

    Because I am not good reading specs, would this meter fit my needs? http://www.uni-trend.com/UT71D.html they have a bunch more meters, but I am not sure if those meters fit what I need either. Their full list is here: http://www.uni-trend.com/product.html I feel the UT71D is a bit overkill, it's priced I think around $130-$150....
     
  19. scieqp

    scieqp

    12
    0
    Aug 8, 2012
    In addition to the above, I should ask this also because until now I cannot find where to get one. Are their any websites out there specializing in selling used NI devices? Ebay has had a few but almost none for the 6210 or 6212. And most sellers I think do not want to list this kind of thing on Ebay because most people don't know what it's for. I've checked around, but cannot find anywhere online that might actually sell some of these used..

    I also was looking at some AMPROBE BY FLUKE multimeters, but have not had enough time to go through all their products.
     
  20. scieqp

    scieqp

    12
    0
    Aug 8, 2012
    Did you all give up on me?
     
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