SignalExpress TE Very Slow Getting Signals

[Bentech]

Hello,
  I have LabView SignalExpress 2.5.1 with Tektronix Edition 2.5.0 and a TDS 2004B connected via USB. The software is the 30 day trial with a few days left.

  When I simply start a new project, and add a step to aquire a signal, then run the step, it takes a very long time to get the signal! I timed it at about 7 or 8 seconds! I was under the impression that you can do logging and get samples quite fast so I think this is very slow. Has anyone else had this problem or know of a solution?

  I had an older version of SIgnalExpress installed a while ago when I first got the scope and I dont remember it being so slow. Is this a bug in the new version?

  Also, when the software is run, it takes control of the scope. If i uncheck the "SignalExpress controls instrument" in the step options, I can then change the setup using the scope controls which is fine. However, the display does not show a real time signal. It just shows a sort of greyed out version of the last aquired signal, and it says "Acq Complete" in red at the top. Cant I get the scope to run as normal so I can see real time signals and just grab a sample when I run the step in the software?

Cheers,
  Carl

[Bentech]

Ok, forget about the last bit, I realized that you can hit run/stop and the scope will continue to function as normal. However I still cannot see why it takes so long to aquire the signal data!? Any ideas? The computer is not exactly slow, it is an AMD X2 Dual 3800+ with 1GB RAM running Windows XP SP2.

[TobyHex]

Hello BenTech,
I want to make sure that I am understanding you completely before making any recommendations. When you add a step to SignalExpress, I assume you are then choosing Tektronix, acquire signal, and then your device. Once the device is chosen, it takes around 7 or 8 seconds for the device to start communicating to SignalExpress? It usually takes this amount of time to initialize the device and begin communication with the device. Or is it when you actually hit Run, that it takes 7 or 8 seconds to begin taking in samples? Also, do you mind telling me what your Record Length is set too under the Horizontal Tab? The reason for checking this is because this can slow down the data acquisition a little bit due to the higher amount of samples being taken in.

Regards,

Nicholas K

[Bentech]

Nicholas,
  Thank you for your reply. When I create a project and choose the TDS200B series it automatically adds a step, but yes it is the same as going add step->tektronix->aquire signals->tek TDS1000/2000.
  I ran the program this morning, and by default it runs on a continuous loop with the one step. It takes 7-8 seconds to start, but then I realize it takes about 2 seconds to update with a new screen of data. When I was doing it yesterday, I was using the Run Once button where it takes 7-8 seconds to do get one lot of data. Why does it take so long for the Run once and for the first iteration if it loops? And is 2 seconds per "data grab" normal? I thought it would be quite fast.

When I hit run once, it says "running once" for about 3 seconds at the bottom of the task list, then it says "Waiting for trigger" for about 1 second then it says "running once" again for about 3 seconds. The scope is continually being triggered however as I have the probe attached to the 1kHz 5V output on the scope.

As for the record length, I have the "SignalExpress controls instrument" disabled so these options do not take effect. However if I enable them the record length is disabled. This is because I have a TDS2004B which has a fixed record length which is 2500.

Cheers,
  Carl

[TobyHex]

Hey Carl,
I was wondering if you might be able to try the same setup on another computer so that we can narrow down the problem. The delay you are saying after the initial add step of 7-8 seconds is pretty standard as mentioned before. The concern comes in where you are seeing a 2-3 second delay after the initialization. Let me know if you are unable to try the setup on another PC and we shall determine the best route to proceed with from there. Also, you mentioned previously, that you were not seeing these types of delays with an older version of Signal Express. Do you recall what you were experiencing for refresh rates then? The setup that I am testing on is using the Tektronix 4000 series Scope connected through USB and we are unable to reproduce the same refresh times at the moment. Thanks again and have a great weekend!

Regards,

Nicholas K

[Djeepee01]

Hi,

has this thread been resolved? I am using a TDS2004b through a labview vi (not signal Express) and I seem to have the same problem. No matter what settings I use, I get a signal refresh time of approximately 1-2 seconds. Is it not possible get some form of continuous acquisition?

Thanks,

JP

[Efrain_G]

Hi JP,

I am not sure if this issue was resolved already, however I wonder if this issue could be hardware related. Does the TDS2004b use USB 1.0, or 2.0?

As far as your VI, is there any structure that could be slowing down your VI such as a While Loop with a Wait VI inside of it?

[Djeepee01]

Efrain,

From the Tektronix data sheet, the TDS2004b seems to be USB2.0. For the VI, I don't see what could be slowing down the transfer. I have attached a simplified copy that still does not allow ''seamless'' acquisition.

Thanks,

JP

[Efrain_G]

Hi JP,

It is quite interesting that you are getting a slow transmission of data through your USB 2.0 port. I wonder if it would help if you tried updating your USB drivers in the Device Manager. I also think that it could be a good idea to try to isolate the problem by reading only one channel at a time instead of running that while loop that reads from all your channels. Let's see if reading a single channel is also slow.

[poemanji]

Hello,

This thread may be cold... but if anyone is reading this, I have a Tektronix TDS1002B.  It takes, at best, ~900 ms, to read the frequency value on channel 1 using the Tektronix supplied LabVIEW instrument drivers.  I'm trying to do 3 immediate reads as quickly as possible.  Does anyone know of a faster way to poll a similar Tektronix oscilloscope via LabVIEW?

Thanks,

Brian