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BNC Adaptor


Question

Hi, 

I was asked by the sales person to make a post on this forum about my issue with the BNC adaptor that I got from one of the vendor.

Setup: 

The current setup is attaching the Analog Discovery 2 (AD2) with the BNC Adaptor. We use the Waveform software and connect the AD2 via USB to our laptop.

We try to conduct a basic connectivity test by connecting the oscilloscope probe into CH1 and have it set to DC. We set the oscilloscope to 10x on the probe itself. For W1 on the BNC adaptor, we attach a BNC cable with two alligator clips (red and black). We set it to 0 ohms setting. We clip the red alligator clip with the main oscilloscope probe and the ground probe of the oscilloscope to the black alligator clip. We are testing if it can produce simple square waves. 

On the Waveform software, we create a new Wavegen tool instance in Waveforms and set the W1 to output a 1 kHz, 1 V amplitude square wave with 0 V of DC offset. Next, we create a new Scope tool instance in Waveforms and make sure that the attenuation for the channel you are using is set to 10X by clicking the gear icon next to the channel name on the right-hand side of the Waveforms window. Click the run button and adjust the voltage and time scales until approximately two square periods of the compensation waveform are clearly visible.

Issue:

We want to make sure the other inputs (W2 and CH2) can do the same thing. However, I try several times and it only produces noises instead of seeing 2 square periods of the compensation waveform. I try to zoom into the signal in case it was too small to see, but it still only outputs noises. For the W1 and CH1, it clearly works since it actually does generate the two square periods of the compensation waveform. 

 

Edited by David Au
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HI @attila

First sorry on the format. I am new on how this forum works in replying to someone on this thread. 

I attached 3 different screenshots. The 2nd screenshot is the wavegen where it remains the same for both CH1 and CH2 with that respective W1 and W2. For the 1st screenshot, it is from CH1 & W1 where you can see the waveform is compensated and outputting a signal. The 3rd screenshot is from CH2 and W2 with the exact setting as 1st screenshot and it does not output any waveform. If I try to zoom in, it is just pure noise. 

 

8 hours ago, attila said:

 

 

 

 

Screen Shot 2020-10-09 at 10.00.00 AM.png

Screen Shot 2020-10-09 at 10.00.07 AM.png

Screen Shot 2020-10-09 at 10.02.07 AM.png

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Hi @David Au

1. Please try loading the Factory calibration under Settings/Device Manager/Calibrate/Reset.
To exclude wrong calibration of Wavegen 2 or Scope C2.

2. Try the loopback with the wire kit.
This to exclude problems with the BNC adaptor or cables.

3. For warranty and replacement the support at digilentinc dot com specifying the Date of Purchase, Seller and Purchase Order/ Web order Number

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Hi @attila

 

1. The calibration for this Analog Discovery 2 (AD2) has no issue with other BNC Adaptors. I tested with 3 random BNC Adaptor that I currently had in possession. It is the reason for suspecting that it is this particular BNC Adaptor instead of the AD2.  

2. What wire kit are you referring to? I currently only have AD2 with its jumper wire and USB-to-Micro-USB cable. The BNC Adaptor does not come with anything else. 

 

3. I might try this since it is only a month since its purchase. 

 

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Hi @David Au

Do I understand correctly that you have identified that the problem is with one BNC Adapter and the AD2 is working well with other adapters?

If you want you could take a look at the Adapter PCB, eventually fix some cold solder or short. This may be quicker than the replacement.
To identify if it is an issue on the Scope 2 or Wavegen 2 lines, you can verify Scope 2 with Wavegen 1 and Wavegen 2 with Scope 1.
Here you can find the simple schematic of the Adapter:
https://reference.digilentinc.com/reference/instrumentation/bnc-adapter-board/start

You can also contact the support for replacement.

Regarding the verification with "wire kit" I was referring to something like this:
image.png

Edited by attila
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Hi @attila

I do not have the wire kit that you have shown above. Yes. I was able to narrow it down to the BNC Adaptor since the AD2 works well with the other BNC Adaptor that I currently have. I have tried your suggestion on isolating the issue between Scope 2 and Wavegen 2 and it seems that the issue is from the Scope 2 connector. From a glance, I do not see any cold solder or anything that would have short it. I am not sure if it is something internal of the Scope connector that might be the cause of the issue. 

-David A.

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