How do I set the NPLC on a Agilent 34970A then keep it set when I do a Temp measurement on the channels

[1tech]

I have an Agilent 34970A DAQ that I am trying to set the NPLC to 10 and keep it set when I issue a temp measurement command to the channels.  Right now I can issue the NPLC 10 command to set the channels and it works but when I send the measure channels command the NPLC gets set back to 1. What am I missing to keep this from happening?


Thanks in advance for your help.

Charles

[EEsRULEtheWORLD]

Hi Charles,

Are you using the Agilent 34970A Instrument Driver?   If so, are you using one of the examples that install with this instrument driver to set the NPLC?

How are you seeing that the NPLC gets set back to 1?  I'm guessing that there is a reset embedded in the subVI that is responsible for the measuring of channels.  Could you tell me exactly what subVI you are using to send the measure channels command?

[1tech]

Hi Sara,

I am was trying to use the Labview Instrument drivers for the HP 34970A and I can not find in any of them that sets the NPLC.  I can issue the skippy command via labview(EZ Temp vi) to set the NPLC to 10 and I can look at it via the front panel.  Then I issue the read temp skippy command via labview(EZ Temp vi) and I get the temp but the NPLC is set back to one when I view it via the front panel.

I also ran NI SPY and could not find anywhere the reset command is being issued.

I am using a modified version of the EZ Temp vi so I can contol the skippy command going in. 

If you need more info to help me please feel free to reply.

Charles.

[JimmyJin]

Hi Charles,

Was your problem solved? I have run into a very similar situation but instead of HP 34970A, I have a HP 3852A and I want to set NPLC small so that it speeds up the data acqusition.

I tried Measurement and Automation Explorer and use "communicate with Instrument" under GPIB folder and issue the command "NPLC 0" before running labview. But I did not see any change when I run my LabVIEW again. Since this command was working under VEE Pro, I am guessing the setting for NPLC was somehow reset. I am not sure why.

I will try use "GPIB write" vi to see if it does anything but I'm not sure if I should set NPLC value everytime. Please let me know what you think if by any chance you see this message.

Thanks,

Jin

[ben64]

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@JimmyJin wrote:

Hi Charles,

Was your problem solved? I have run into a very similar situation but instead of HP 34970A, I have a HP 3852A and I want to set NPLC small so that it speeds up the data acqusition.

I tried Measurement and Automation Explorer and use "communicate with Instrument" under GPIB folder and issue the command "NPLC 0" before running labview. But I did not see any change when I run my LabVIEW again. Since this command was working under VEE Pro, I am guessing the setting for NPLC was somehow reset. I am not sure why.

I will try use "GPIB write" vi to see if it does anything but I'm not sure if I should set NPLC value everytime. Please let me know what you think if by any chance you see this message.

Thanks,

Jin

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I don't think you can set the NPLC to 0, the minimum value is 0.02. Maybe VEE automatically set it to the minimum value. Instead use NPLC MIN.

Now if you use the MEAS? command to read the value the instrument will use the default value for the type of measurement if you don't specify the resolution (not the integration time, if you look at the 34970A documentation you will see how they relate) which is probably set to NPLC 1.

If you want to speed up things you may look at the ROUT: SCAN and READ? commands to define a scan list.

Ben64

[Arda____]

Hi, ı saw this problem on my Keysight DAQ 970A, Can you find any solutions for this problem?

[NIquist]

All of the posts above seem to be saying that the NPLC parameter is somehow changing by itself which makes no sense.  I have used the DAQ970A and older 34970A instruments for many years and never saw an issue like this.  It is VERY likely that they were all doing something wrong in their code which reset the value, but since no one posted any code there's no way to check.

Please let us know what you are trying to measure and which modules you are using.  Also, post your code!  It is almost impossible to troubleshoot a problem unless we can see what you're doing.

NOTE:  If you are using a recent version of LabVIEW (> 2000), please do a File > Save for Previous Version... and save it for LV 2018 or so.  I'm still stuck with 2019 and many of us here that can help are also using older versions. 😉

[RTSLVU]

You are probably doing it wrong... Without seeing your code I am guessing that you are using the "EZ" VI set or the SCPI MEAS: command. 

While this works for single channel measurements at relatively log intervals, it is not how you take multiple measurements of different types in one scan like the software that comes with it.   

Do use this instrument properly you need to drill down to the advanced configuration VI set.

Configure all your channels measurements and build a scan list

When you need to take a measurement use something like this to trigger a scan and retrieve the data.

A for the person using the new Keysight DAQ 97x series. I recommend you use the Agilent 34970A drivers as the DAQ97X is fully backwards compatible. 

[Arda____]

My code is very simple, I didn't add anything else until I solved this, because scan time is important. I will try the 34970A library. 

[Arda____]

actually ı try to set 0.02