Getting data from the Impedance Analyzer 4294a

[zingkov]

First of all, I must admit that this is my very first time using Labview. What I have done so far is merely following some basic examples provided in the wonderful NI demos/webcasts.

What I want to do now is simple:

1. Reproduce the graph displayed on the screen of Agilent Impedance Analyzer 4294 in Labview Front Panel.

2. Save all the data into my computer hard disk in either txt or EXCEL format.

I am using Labview 8.5 (with GPIB connection). I have downloaded the NI 488.2, NI VISA and NI instrument driver for 4294a. The connection worked just fine. I have browsed through all the provided examples in the driver. However, most of the examples only display the measurement value of a specific parameter. None of them show the entire graph or allow us to specify the folder which I want to store the entire data to. I suppose with simple modifications at the Labview block diagram, this can be easily done. But I just have no idea how to do even that.

I earnestly hope some experts here can give me some clues. Thank you very very much!

[smercurio_fc]

I'm not familiar with that instrument, but I took a quick look at the instrument driver for you. Not sure which one you downloaded. I pulled down the project-style one found here. Drivers obviously won't have all possible examples, but I believe that all you need to do to get the data is to use the "Read Data and Memory Arrays" found in the "Public\Data" folder. This will provide you with an array of values that you can wire directly to a graph. You can also wire this directly to the "Write to Spreadsheet File" VI in the "File I/O" palette. For that VI if you leave the path input unwired you will get a dialog asking you where to save the file. It's usually better, though, to provide a front panel path control.

[zingkov]

Thank you smercurio_fc for the comment. I appreciate and I will try your method.

By the way, may I know the main difference between the Plug and Play (project-style) instrument driver as compare to the Plug and Play instrument driver? I previously only downloaded the one without "project-style". Thanks.

[smercurio_fc]

Usually the difference is in the organization. The project-style drivers have individual VIs in separate directories organized like a project, and using a project file. The "regular" drivers are typically packaged as a library (.LLB) as usually 2 files and associated menu files. Depending on when they were written there will be differences in implementation and examples. As far as what those difference are, you can't really say, as it depends on the drivers and when they were written, as well as by whom.

[Sendtohen]

I have downloaded the drivers.  I was able to get the data, there seems to be some performance issues.  I was able to capture the data, but when I try to read it out it is given me a VISA:  (Hex 0x3FFF0006) issue and the error code of 1073676294.  I know this is a number of byte problem, but I was not able to resolve it. It is take really long while my requirement is on the order of milisecs.  Please advice.

Henry

[smercurio_fc]

Was that an actual error? Was the "status" boolean in the error cluster actually on? If not, then that's a warning (using NI's error/warning convention). My guess is that you're using a serial connection, and that you have termination character enabled, meaning the read is stopping once it sees the termination character (probably a linefeed).

As for your speed issue: I woulnd't count on getting data that fast, especially if you're using serial. Even GPIB is questionable since you have so many software layers to get through. If you have high-speed requirements you may need to look at alternative ways of getting the data, such as using a DAQ board.

[Sendtohen]

I am sorry, maybe I am not being clear enough.  I am collecting data through GPIB.  I am using the downloaded drivers.  Whenever I try to collect a set of data, it would take over 10 secs.  As i track the timing of each sub vi.  I tracked it down to the "Read Data unknown length" inside the "Read Data and memory array.vi" which takes up most of the time.  Is 10 seconds normal?

 I would just like to collect some data at the speed of 1 sec.  Any help would be appreciated.

Henry

[smercurio_fc]

That sounds like a timeout issue. That subVI just loops around until the VISA Read returns with no bytes. Seems a bit clumsy to me, as you can get into a situation where a single read could return no bytes, yet there's still data there. One thing that you can try is to replace the call to the "Read Data Unknown Length" with a VISA Read in which you wire a really big number for the number of bytes to read. The VISA Read will read as many bytes as available - basically until is sees EOI. Sort of like this:



You will need to determine what a sufficiently large number is based on the number of points and the data size (i.e., number of bytes per point). This should be in the instrument documentation.


Message Edited by smercurio_fc on 06-14-2008 11:36 AM

[anuragdhutti]

Hi, has anyone tried connecting 4294a over ethernet?

[Dennis_Knutson]

The driver page says it supports Ethernet so if you have a problem, describe what it is. Also, since this is an old thread and your problem is unrelated, you should start a new one.