USB1808x output glitch

[jpavlich]

I am noticing a 'glitch' on the analog output. I am working with 1000Hz triangular output and I see a glitch in the same spot of each cycle.  I can put this signal on an oscilloscope and also see the glitch.  I have attached a file to show the glitch in DAQAmi.  I have the same output on both channels.  In the attachment, I have tied AOUT1 to Ch2.  Have you seen this before? 

glitch.pptx

[Fausto]

Hello @jpavlich.

Please check your wiring and test the USB-1808X with a different system.  I set the analog input sample rate to 200 kHz and the channel mode set to differential.  Below is my result. 

 

What is the serial number of your USB-1808X and have you had any issues with it in the past? 

Regards,

Fausto

Edited September 6, 2023 by Fausto
differential mode

[jpavlich]

Hi, we have just started using this device.  The serial number is 2151488.  I have the output hooked up with a twisted pair from AOUT1 to Ch2 in a single-ended configuration.   I will try this on another computer tomorrow. I can change the voltage range sweep and still get a glitch but in a different spot.  But it remains consistent to that spot.  Could it be that the sweep is too fast?   I will try a slower sweep as well.

[Fausto]

@jpavlich,

It may be a display glitch.  Save the input data to a .csv file.  Open the data file in Excel and plot the data.  Do you still see the glitch, using Excel?

[jpavlich]

I did try it on another computer and saw a similar glitch.  I also plotted in python and looked at the output signal on an osciloscope and saw the glitch.

 

[jpavlich]

I am trying the 1698GX-2AO and am having better luck with the DAQAMI software.

but I am having trouble with the python code.

this is the output I am getting on ch0 (AO1 to Ch0),  I can see on the scope that the output from AO1 is okay via the python code, which is a triangular display.

 

Not sure what is going on in the python side.  If I have the instacal set up for single ended that should work correct?   Should I not be using scaled data with a 1608Gx?  I will attach my code.  Thanks.

 

a_out_scan_cont_1608G.py

[Fausto]

@jpavlich,

For the USB-1608G Series, the SCALEDATA option is not supported with the a_out_scan() function.  Please reference the Universal Library Help file for supported functions.

https://files.digilent.com/manuals/Mcculw_WebHelp/ULStart.htm

 

Test the attached a_out_scan_1608GX_2AO_v1a.py example. a_out_scan_1608GX_2AO_v1a.py

The output should be a +/- 10V square wave.

Regards,

Fausto

[jpavlich]

The output on the 1608Gx  seems to be working okay.  but the input scans are a little strange.   I have the ch0 input tied to 5V but the reading is moving around when I run some of the sample scripts.  Here is ULAIO2.py output.

 

 

But If I run the Daqami app I get an appropriate output.

 

Here is another example with the a_in_scan_background.py output.  Where Ch0 is at 5V and Ch1 is grounded, Ch2 and Ch 3 are not connected.

 

I feel like the unit is working okay since the DaqAMI output works but I'm not sure what is going on with the mcc examples.  No change in wiring between the runs.  Any thoughts?   Appreciate the help.

[jpavlich]

Just another data point. Instacal seems to be reading appropriately.    So I'm just having trouble with the python examples.    Thanks for the help.

 

 

Here are some example runs from a_in.py which is looking at Ch0 which is tied to 5V.