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MSOX2012A WaveGen Option Voltage output problems

Question asked by ertr on Jun 18, 2012
Latest reply on Aug 8, 2012 by ksmith

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I have a Agilent 2000 oscilloscope with WaveGen option installed. I am using to test an ADC Module from TI, specifically it is ADS1278EVM module.

I have the WaveGen generating a 5VPP sine wave with no offset voltage. When I connect my oscilloscope input to the wavegen output I see the sine wave but the voltage is showing 0.3VPP (about 0.3V~, rms, I also have the DVM Option installed). I see this both with high-z setting and 50ohm. I have the WaveGen ground connected with the oscilloscope ground.
This is exactly what I observe through my ADC module as well (I have an fpga as my dsp connected to my computer).

Can you please advice why am i not seeing the full 5VPP?

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algoss Jun 19, 2012 9:07 AM
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I think that you have a problem with your WaveGen. I have a 3000 series, and I connected the WaveGen output directly to channel 1. I'm seeing 5.27V pk-pk if the scope is set to high-Z, and 2.69V pk-pk if the scope is set to 50 Ohm.

I don't know what the input impedance of your device is, but unless it's High-Z, you won't ever see 5V pk-pk.

Al
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- ertr @ algoss on Jun 19, 2012 7:36 PM
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  Here is an image capture attached, so does this mean I have something wrong with my WaveGen?
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  - scope_0.bmp1.2 MB
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  - algoss @ ertr on Jun 20, 2012 4:29 AM
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    Yes
    
    Al
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    - ertr @ algoss on Jun 20, 2012 6:22 AM
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      So what do you suggest i do? I just bought it and they installed the WaveGen option at the factory before shipment.
      Thanks!
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      - algoss @ ertr on Jun 21, 2012 5:22 AM
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        I don't know where you are or where you bought it, but you need to call your local support number and arrange for repair.
        
        Al
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bret Jun 21, 2012 9:18 PM
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Sending it back seems to be the best bet, but you could also try a Self-Calibration.
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- algoss @ bret on Jun 22, 2012 4:32 AM
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  Yes, self-calibration is an option. It uses WaveGen to generate the various waveforms necessary for the cal process, so if there is a problem with WaveGen, then the cal will fail.
  
  Al
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  - ertr @ algoss on Jun 22, 2012 7:48 AM
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    Thanks for all the help! I just shipped my unit back for replacement. They confirmed the problem as well.
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ertr Aug 8, 2012 7:05 AM
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Well I got a replacement one back just now. Connected it the same way and here what I see. I must not be setting a value right or something. Can you please see the images below. It shows how I connect the probes (N2862B) together at 5V wavegen option active. Please let me know if you need more info.
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- 2012-08-07 22.35.24_2.jpg2.6 MB
- 2012-08-07 22.37.18_1.jpg2.6 MB
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- ksmith @ ertr on Aug 13, 2012 1:38 PM
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  Hi,
  
  A picture is worth a 1000 words.
  
  1. Since you are using two 10:1 attenuating probes in series... you are attenuating the signal by a factor of 20 (10+ 10 = 20 ; these add like series resistors; it's not exactly 20, but that's close enough). 5, 000 mV / 20 = 250 mV. This is spot on. if you set the probe attenuation value to 20, you will get pretty close to 5V.
  
  2. Connect the wavegen out to CHx by with a BNC cable; make sure CHx is at 1:1 (which it is in your photos). Leave the wavegen at High Z; set 5Vp-p, you should now see ~5V p-p on CHx, since it is a HighZ only input.
  
  3. When you go to use a a probe, this scope does not ID the probes, so you hve to manually tell the scope what the probe attenuation ratio is for the screen to read the rigth value. All the probes that came with the scope are 10:1 probes.
  
  4. In the plastic bags that the probes cam in, you should find a small silver/chrome barrel. This is a probe tip to BNC adapter. Put the adapter into the wavegen output, remove the hook tip and ground lead from the probes, and insert it into the adapter. Set the probe attenuation to 10:1. You should see ~ 250 mV Vpp. kinda like the attached.
  
  Edited by: ksmith on Aug 9, 2012 10:12 AM
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  - BNC-probe.png299.1 KB
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MSOX2012A WaveGen Option Voltage output problems

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