National Instruments 54602B Oscilloscope

[drbr0wn]

Hi.

Downloaded/modified an oscilloscope vi to control a single channel input, read and record wave functions from sEMG in a csv (Excel) file. The oscilloscope refreshes at a rate of approximately two periods/sec and records each period within a fixed set of 1000 cells in Excel.

How can I make it so the refresh rate is longer so that I can actually viably record the wave signals I am attempting to capture? It seems that with each motion, the oscilloscope refresh and actual motions are never synched up.

Thanks.

[Dennis_Knutson]

There is no such thing as a National Instrument 54602B. There is an Agilent scope with that model number. I'm going to assume that is what you really have.

Since you modified an example VI, why don't you go ahead and attach it so everyone can see what you have done. Be sure to enter values into the front panel controls, go to thr edit menu and select 'Make Current Values Default, and save the VI before attaching.

Also explain what you mean by 'make it so the refresh rate is longer'. Do you mean you want to acquire more samples at the existing sample rate? What do you mean the refresh rate and motions are not synched? I hope you are not expecting to see continous data on the scope. The way a scope works is that you will trigger an acquisition, the scope will capture x amount of samples, it will transfer those samples. While the transfer is being done, you will not be capturing so there will be some large gap in the motions.

[JÞB]

You know I've allways thought that the horizontal properties in NI-Scope were a bit of a problem too.

I came from a technician backround- I like knobs and dials!  Even the soft front panel for NI- scope gives you a "Time per division" control yet, the guts use Sample rate and Number of samples.  It is an easy transition if you know two things-  1) how fast you want to sample.  2) how much time you want to return in a given record (pre and post trigger) 

Say you want to acquire a record of two cycles of  a 10KHz square wave-  You'll need to sample at a rate greater the the freq of interest (oversample) so set min.sample.rate to 20KHz and set the min.record.len to 4.  You'll get 2 Highs and 2 lows.  Sample rate TIMES number of samples gives you total time returned for any given record.  It may not be intuitive for a guy that likes to turn the "time per division" knob but, that IS the differance between a "Digitizer" and an "ocilliscope."  NI-Scope runs "high speed digitizer's"- O'scopes are for techs to look at

[drbr0wn]

Please check out the attached vi.

We're trying to set the sampling rate; however, we can't find the control/option in the block diagram. The vi, when executed, saves 500 data points/second (Range (t) = 1 on the front panel) or 1000, but we cannot stray from those two values, even if the control (0-8: 100-4000) is modified prior to running the vi.

Thanks for your response.

[Dennis_Knutson]

Your horizontal range is set for 6usec or .6usec/div and you are acquiring 4000 points in that 6usec. Your numbers do not agree unless you did not save your defaults like I asked.

There is no control to modify the number of samples unless you are talking about the one on the subVI. Of couse, modifying that does nothing unless you actually made that a new default. Since you did not seem to understand how to do that on the mina, you probably did not do it correctly on the subVI.