Increasing the scan rate for Keithley 2700 f AC Voltage measurement

[oap3952]

The error is shown in the "timing vi" of the "keithleyperformance.vi". I am using Rs-232 to Usb for connecting the keithle 27xx to the computer. Using Labview 16 for running the code.

[cstorey]

What values are you sending to the timing VI?  Just the defaults?  Did you supply Power line cycles and a value of 0.02?  Try 0.1 or 1 or 5.  Do those work?  Try the aperture and a time value (10ms)?

The more details you provide the less guessing we have to do the quicker you get an answer..

Without any knowledge of what card you are using its going to be up to you to debug.

[oap3952]

I am using a keithley 770 20 channel multiplex slot card. I ran the code at default value.

[oap3952]

I tried sending all the different values to Timing.vi but it gives the same error of 221:System Conflict

[BrinkHombre]

Hey oap3952,

Can you read data from your original example VI anymore? Or is the error 221 system conflict keeping you from collecting any data? I am trying to figure out if we took a step backwards, or if we are still troubleshooting the sampling rate.

If you can't connect to your device in LabVIEW, can you see it in NI MAX? Can you successfully communicate SCPI commands in the VISA Test Panel?

Best regards,

[oap3952]

Nope, we took a step backward. i can no longer read data from the standard "Peformance.Vi" The error 221 prevents from reading data. Yes, I tried to communicate using the Visa Test Panel. I sent a query and it read backs with No Error. Whenever I try to use "Timing.Vi" It shows the error of "System Conflict"

I have attached a very basic vi to reply. This vi works without the timing.vi at slower sampling rate of 1 eading per second. But as soon as I use timing.vi to adjust aperture timing or NPL Cycles it Shows "system conflict"

[cstorey]

I don't see a 770 card listed as compatible with 2700.  Have you checked the specs? 

I'm guessing that AC voltage measurements can't use NPLC or other measurement timing setting because they need to do more averaging to get a measurement.  What's the frequency of your signal?  What does the card documentation say about AC measurement rate?

[RTSLVU]

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@cstorey wrote:

I don't see a 770 card listed as compatible with 2700.  Have you checked the specs? 

I'm guessing that AC voltage measurements can't use NPLC or other measurement timing setting because they need to do more averaging to get a measurement.  What's the frequency of your signal?  What does the card documentation say about AC measurement rate?

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Well in general NPLC is used for AC/DC voltage measurements when noise is an issue. The NPLC is literally the Number of Power Line Cycles the instrument averages the measurement.

I usually do not use NPLC unless I am measuring in the 100mV range such as measuring voltages across a current shunt.

[oap3952]

I am attaching the manual and data sheet for 7700. I have checked it. I am measurin an AC voltage in a range of mV. For jut test runs, I am giving the Keithley 27xx a signal of 100mV at 1kHz.

[cstorey]

So if you just conditionally disable or remove the timing VI for the moment then everything else works?  What sort of increase in speed do you see with 3.5 digit resolution and autorange disabled?