Hello all, I’ve been running plots of my various and rebuilt volt standards (aka DAS-46 which we have working now) and during that process, someone mentioned to me about using two meters at once and then correlating the outputs. I have a pair of both 3457a’s and 3456a’s, and though the 3457a has the extra digit, the 3456a meters seem to be more stable. So assuming I get a time-stamped dataset from both meters, for instance the 3457A meters in hi-res mode, would I just average the two samples? And if so, would that add a significant level of accuracy for me to change the code, which will only take about 10 minutes maybe? I guess it could remove some noise, no? I could actually run the two from two visual basic programs, triggered by a software pipe, so instead of reading the meters from one program sequentially, I can trigger both programs from a 3rd program using a pipe. What do you think? I’ll probably play around with it today, but was wondering if there was higher math needed than just say averaging the data sets by point. In NPLC=100 mode, the 3457A read loop is a little less than 4 seconds using visual basic. I generally grab about 7,000 to 10,000 data points. Thanks.

-------- In message <3EE48329-EDB5-44D1-AB6C-68C81777DD6E@hanler.com>, Jerry Hancock writes: >Hello all, > >I’ve been running plots of my various and rebuilt volt standards (aka DAS-46 which we have working now) and during that process, someone mentioned to me about using two meters at once and then correlating the outputs. I have a pair of both 3457a’s and 3456a’s, and though the 3457a has the extra dig >it, the 3456a meters seem to be more stable. > >So assuming I get a time-stamped dataset from both meters, for instance the 3457A meters in hi-res mode, would I just average the two samples? First thing you should do is plot them in X:Y mode and let that graph guide you. If you get a straight line from lower left to upper right, the two meters track each other and averaging will get you little more than a sqrt(2) reduction in noise. If you can, also record a representative room temperature, plot that on one axis and the two meter readings on the other, then think creatively about the result... -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.