Cannot Sample Above 150 hz

[CQDevelopment]

Hello, I am currently trying to run a frequency response test by applying a sine wave to an object and then observing its response. Attached is my code-I tried using a sampling clock tied to a control on the front page to determine the sampling rate that the user wants the data to be taken at.

The problem I'm having is right now I cannot get samples above 150 hz regardless of what I set my sample rate to-everything appears to be working but when I time the data myself I realize that it's only taking 150 samples per second.

I tried changing the settings on my sample clocks all over the place with very little success-at one point I was getting 200 pts per second but messed something up, tried to redo the code that I had but it didn't work out.

Also I'm aiming for about 1k samples per second.

Thanks!

Message Edited by CQDevelopment on 08-24-2007 11:30 AM

[Dennis_Knutson]

What you are doing is confusing. You have a task called 4-20 mA Out that you have wired to both a DAQmx Read and a DAQmx Write. You can't do that. You also have a task called Position Transducer for another DAQmx Read. Unless your have a separate DAQ board for this task, you can't do this either. Wire up some error indicators and see if you are generating some errors.

[CQDevelopment]

Sorry let me clean it up abit


And why would I need a separate DAQ board for the position transducer? I'm reading from a different channel than the one I'm writing with.

Here's a cleaner version.

[Dennis_Knutson]

With your two separate DAQmx Reads, you would need to have two separate DAQ boards. Let me look at your modified VI. What DAQ board are you using?

[CQDevelopment]

I'm using the PCI-MIO-16E-4

Have a 5b backplane and a CB50 LP terminal connector both hooked to a SC-2050.

The system I'm using now hasn't ever had two inputs before, but we have a few other daq systems around that all have multiple inputs that run concurrently.

I'm new to Labview and daq in general and so I'm still really confused why you'd need multiple cards to read multiple inputs.

[Dennis_Knutson]

You don't require multiple cards for multiple inputs. What you can't do is have multiple tasks of the same type on the same board running at the same time. That is why I said you can't have the two separate DAQmx Reads without two separate DAQ boards. The information about the DAQ board and the channels used is buried in the task you created in MAX. That's one of the reasons I don't create the task in MAX.

[Dennis_Knutson]

I had to do quite a bit of cleanup to your program to see what you were actually doing (please read the sytle guide) and the attached VI is what I came up with. One of the problems is that you were using 1Ch 1Samp for the DAQmx Read. When you do that, you are switching to software timed acquisition.

[CQDevelopment]

Thanks for the tip, I'll check it out now!

Message Edited by CQDevelopment on 08-24-2007 01:27 PM

[CQDevelopment]

Checked out your mod and I'm still only gathering about 100 pts per second max. Could it possibly be some configuration issues with MAX and if so where should I look?

[Dennis_Knutson]

I don't think it's a configuration issue in MAX. I have to run the VI in simulation mode but with a sample rate of 1000 s/sec, I get 1000 samples with each DAQmx Read.