Data Acquisition Idea Exchange

A customer of mine was trying to read 8 thermocouple readings simultaneously over the course of a week and then store the data.  She quickly found out that there are memory limitations with Signal Express.  Eventually no matter how She saved or logged their data, she would run out of memory.  My product suggestion is to write code that will determine the RAM on a customers computer as well as available hard drive space and show customers (at the start of a task) exactly how long they can acquire signals without filling up their hard drive or seriously draining their resources.  That way when they start a process, they are aware of what they're working with in terms of space at that instant rather than when an error pops up three hours or so later.  Most customers would figure out these needs in advance of any acquisition, but for the ease of the customer, this would be a welcomed additional feature.  It would also be nice to have a document that explained how this time frame was calculated.  I suggest that when a task is ran, there is a pop up that explains the maximum amount of samples that can be acquired and time that can pass.  The document I mentioned could be available via hyper-link, and the hyper-link text could read "How did we calculate this number?", which could explain the process in more depth.

I have submitted this idea for Signal Express at the product suggestion page found at www.ni.com/contact ("feedback" link in bottom left of window).  I figured this would be a good idea for DAQ in general for any extended signal acquisition.

Shawn Shaw

Applications Engineering Department

National Instruments

I'm not sure who reads this, but I'm not seeing any feedback in the forum so I thought I'd post up here.   This may seem like a simple thing, but hopefully my pain will be someone else gain.  I messed with this off and on for two months before I finally figured it out.  It's probably obvious to those who work with this equipment every day and have EE degrees, but not so much to those of us who do not. 

Please see http://forums.ni.com/t5/Multifunction-DAQ/Measuring-220VAC-with-CompactDAQ/td-p/1145956 for a description of the issues I was having. 

Some will tell me to "search"... well, I did.  ...and everywhere I looked all I found was that I needed to measure from the power leg to ground.  All of the examples either were only measuring 120 which is fine since what you have is one power leg and neutral... which is basically ground!  So those numbers come out fine.  Or they were for 3 phase, which I don't use currently.  BUT when you try and measure anything with two power legs (basically anything between 208VAC to 240 VAC) the numbers don't work out right if you try to measure between each power leg to ground and then try to recombine them and plug them into the Power VI's.  Not one place that I looked did it tell me that I need to measure both power legs across a single channel.  I only finally tried it because I'd done pretty much everything else.  I know this is pretty basic stuff, but when all you give me says one thing... that's what we do.  Just trying to help others.

Thanks,

Chad