DT9837E does not acquire correct signal in time domain

[zakir quabili]

The DT9837E does not acquire correct signal in time domain.

The top figure shows the time domain signal (quiet environment) when DT9837E was normal.

The bottom figure shows the time domain signal looks like now after we found something went wrong with DT9837E. The magnitude of the signal is also wrong.

Any suggestions?

 

[Fausto]

Hello @zakir quabili.

Please confirm the Data Translation device used, i.e. DT9837A, DT9857E.

Which operating system and version are you using?

What is the serial number on the backside label of the device?

Open Windows Control Panel Items using 'Control Panel\All Control Panel Items'.

Which DT device is listed?

Reply with a screen capture of the device list (similar to the image below).  Also, select the device and then click on the Advanced button.  Reply with a screen capture of those settings as well.

Which software are you using?

Install the current version of DT OMNI software, with DT Open Layers.

https://files.digilent.com/#downloads/DTSoftware/Omni-CD/

Run Data Translation's QuickDAQ application, which gets installed with the DT software installation.

QuickDAQ defaults to channel 0, so connect a known voltage signal to channel 0.

Start an acquisition and reply back with your results.

Regards,

Fausto

[daquser]

@Fausto

Let me reply to your questions, I am from the same team of the engineer who started this post.

(1) Sorry for the confusion, the model of the device in question is DT9857E (s/n: 1EC8B17) which we purchased not long time ago. 

We use the same version of DT OMNI as you suggested.

Please see below the screen capture from "open layers control panel".

 

(2) As you suggested, we used the QuickDAQ to acquire a sine signal from a function generator (1000Hz, Vpp =0.6V). Below is what we got from the DT9857E (sampling frequency 20kHz).

We see the acquired signal (red line) is not uniform, and is embedded in an unknown low frequency irregular signal. 

 

(3) As a comparison, we used a DT9837A we have to acquire the same signal using the same method (same sampling frequency), and the acquired signal (blue line) is what we expect to see.

I did a sample FFT comparison, it shows the FFT of DT9857E in question shows many peaks which are not from the source signal.

 

 

I was wondering if you have seen similar issue with DT9857E before and what can be done to fix it?

 

Thanks.

[Fausto]

Hello @daquser.

Thank you for the additional information and screen captures.  Your device's serial number was invoiced on 10/12/2021, so it is out of warranty.

When using QuickDAQ, please confirm that only the capturing channel is selected and the other channels are not selected nor have an external signal connection.  Please repeat this test for all analog input channels individually.  Also, test with a different BNC cable to rule out an issue with the actual cable.  Lastly, verify that there is no surrounding equipment (i.e. pumps, motors, EMF sources) that may be interfering with your input signal.

Let me know the results of these tests in order to determine if the device requires servicing.

DT9857E User's Manual:  https://files.digilent.com/manuals/UM9857.pdf

Regards,

Fausto

[daquser]

Hi @Fausto

(1)   We verified that the current issue with DT9857E is NOT caused by BNC cable, surroundings, or external signal connection.

(2)   We checked the 8 channels individually (each time only the capturing channel is selected as you emphasized) and we found that 5 out of 8 channels have the same problem as described in my previous post. The impacted channels are ch0, ch1, ch4, ch5, ch6.    And ch2, ch3, ch7 are still able to capture signal correctly.

[Fausto]

Thank you for testing.

I will send you a private message regarding our repair process.

Regards,

Fausto