problems in communicating with agilent 34970A

[kleinfeld]

hello
i'm using agilent 34970A data acquisition with LV. I'm doing scannings
over 4 channels (10K thermistors) with scan to scan interval of 0,01
secs-0,001 secs.
The problem is that the readings aren't stable at all and the
fluctuations depend on range and resolution; sometimes they look like
square waves, sometimes they are completely random. Any solution?

[Matt_K]

The solution to your problem is National Instruments Hardware. However, if for some reason you decide to continue to use the agilent device, you'll want to make sure you have your signals connected correctly, etc. We have a lot of general information on our website dealing with the basic of Data Acquisition. If you continue to have problems with the product, I would recommend contacting Agilent. They might be able to help you get their hardware working properly.

Matt Kisler
Applications Engineer
National Instruments

[Dennis_Knutson]

I agree with Matt. I use a lot of 34970's (not with thermistors though) and don't find them particularly fast. You might try slowing down the scan rate to see if that improves things. Also, if you already haven't, check chapter 8 of the user manual on measurement fundamentals and sources of error. In any case, I don't think your problem has anything to do with LabVIEW.

[Priyanku_BE]

Hello, I am using an Agilent 34970A and trying to communicate with it using an Agilent 82357A GPIB/USB cable .My LabVIEW version is 7.1. I downloaded instrument driver for Agilent 34970A (for LV 7.1) & installed. In DAQ Max I could able to detect the instrument. But while running ready to use example VI (Advance Scan Example.VI), an error is popping up which  comes even when the Agilent DAQ is not connected to the Laptop. The error message contain:  Error -1073807195 occurred at VISA Open in HP34970A Initialize.vi->HP34970A Advanced Scan Example.viPossible reason(s): VISA:  (Hex 0xBFFF00A5) The interface type is valid, but the specified interface number is not configured. Looking forward for your help on this. Thanks,Priyanku P. Bora

[JÞB]

Matt, and others,

I have done a bit of development work using the 34970A.  I have encountered and solved similar issues with VISA communications with the Agilent driver.  The problem seem to stem from the VISA reads and writes throughout the driver and several issues exist.

1) VISA Write and VISA Read vi's are configured as synchronous throughout the driver and no delay is placed between them.  What this means is the writes return as soon as the data is sent to the write buffer.  With the extended overhead of GPIB via USB the read vi may be called BEFORE the write data is written out to the 34970A.  This is solved by using Asynchronous writes and reads and adding a re-entrant variable delay between the write and read. (start with Wait +(ms).vi but make it re-enterant or your delay will be unpredictable in multi-thread applications).  An Asynchronus write does not return until after the data is sent to the instrument.  To swap between sync and async right click the vi and select the correct option (a clock is shown in the top right of the vi for sync).

2) VISA TMO property is reset depending on resolution of the reading.  This causes all future calls to the instrument to use the new value and could cause unexpected results.  It is much better practice to set the TMO value during initialization ONLY.  If it needs to be changed for a specific sub.vi that sub.vi should A) read the passed in value, B) set the desired value and most importantly C) RESET TMO to the original value before returning!!! (This practice could be applied to any VISA Properties that are changed and just call it VISA Session transparancy.  VISA out = VISA in except in initialization.

I hope this helps 

Jeff

[Dennis_Knutson]

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Communication with BNR PLC wrote:
Hello, I am using an Agilent 34970A and trying to communicate with it using an Agilent 82357A GPIB/USB cable .My LabVIEW version is 7.1. I downloaded instrument driver for Agilent 34970A (for LV 7.1) & installed. In DAQ Max I could able to detect the instrument. But while running ready to use example VI (Advance Scan Example.VI), an error is popping up which  comes even when the Agilent DAQ is not connected to the Laptop. The error message contain:  Error -1073807195 occurred at VISA Open in HP34970A Initialize.vi->HP34970A Advanced Scan Example.viPossible reason(s): VISA:  (Hex 0xBFFF00A5) The interface type is valid, but the specified interface number is not configured. Looking forward for your help on this. Thanks,Priyanku P. Bora

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Your problem stems from using an Agilent controller. You need to enable tulip support in MAX in order to use NI-VISA with the Agilent converter. There may be addtional configuration changes you need to make depending on the versions of NI and Agilent software. I would suggest you search the forum for the Agilent model number.

[RTSLVU]

I have been using the Agilent 34970A's for years, we still have some that say HP 34970A and have several production ATE systems built aruond these.

Anyway I have never ran into the issues that Jeff Bohrer mentioned but I have ran into the Agilent GPIB issue... I am not sure who to blame on this one, but I tend to point my finger at NI since the "Tulip" support is the ONLY support that is turned OFF by default.

Enable Tulip support and try again. If that does not work load the Agilent I/O libraries suite. When using the Agilent I/O lib's you must first go into the Agilent Connection Expert and make sure it finds the 34970A, then Labview will see it because the Agilent I/O also has it's own VISA.

Also the 34970A will not show up as a DAQ device in NIDAQ you will have to use the VI's found in the NI Instrument Driver Network  

[JÞB]

RT

You've probably seen the issue but coded around it in earlier versions of LV.    

[RTSLVU]

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Jeff Bohrer wrote:

RT

You've probably seen the issue but coded around it in earlier versions of LV.    

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I don't think so, but maybe someone else did.

But here is the 34970A 'drivers' I am using

[Priyanku_BE]

Hey Jeff,

I think, I am encountering an issue similar to your point 1. I am using GPIB/USB to communicate with Agilent 34970A. While writing READ?  on VISA & read, I am getting error -420. I could able to get data for 1^st iteration, but there is no data collection in subsequent iteration. You are mentioning about Asynchronous writes and reads to resolve the issue. Could you elaborate the same? I herewith attached my code for your referenc.

Thanks,

Priyanku

P.S:  I have LV 7.1 Version only