EWL diagnosing

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Federico Sangiuliano

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Jul 22, 2021, 6:47:54 AMJul 22
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Hello all. A few weeks ago I hosted an online meeting with the purpose of showing how to diagnose the EWL. Because not everyone was able to attend and I didn't record it, I'll write down the instructions in this post. To diagnose the EWL we need the following 
  1. v4 miniscope
  2. Coaxial cable
  3. DAQ with the latest firmware
  4. A computer with an USB3 port and the latest Miniscope DAQ QT Software
  5. An oscilloscope capable of measuring amplitudes up to 80 Volts 
  6. At least one oscilloscope probe
First, we locate the testing points on the PCB. The EWL needs two terminals in order to work. In the v4 miniscope, the terminals that make contact with the EWL are found in the flexible PCB shaped like rings with an exposed copper trace . The pads on the rigid PCB are electrically equal to those in the rings.
ewl.png
To diagnose the EWL we need to measure the voltage on those test points
  1. Attach the coaxial cable to the u.FL connector in the v4 miniscope
  2. Screw the coaxial cable to the SMA connector in the DAQ
  3. Plug in the USB3 cable into a USB3 port
  4. Open the Miniscope DAQ QT Software
  5. Load a configuration file suitable for the v4 and click "Run"
  6. Check that the v4 miniscope is streaming data to the computer. If the connection to the computer fails don't continue until you can connect the miniscope
  7. Ground the oscilloscope probe. Please make sure that the probe clip is connected to ground before continuing 
  8. Place the tip of the probe on each EWL ring. Record and save the amplitude and frequency measurement
  9. Place the tip of the probe on each EWL pad. Record and save the amplitude and frequency measurement
If the EWL in the v4 miniscope is working correctly a square wave of 70 Volt amplitude and 5 kHz frequency should be measured at any of the test points

SCR24.PNG

If the square wave is not found at the four testing points, we have three cases

Case 1: the square wave is measured in the pads but not in the rings

In this case the EWL circuitry is still working but the rings are not. This can be fixed by cutting the rings and soldering a new EWL cable in the pads

Case 2: the square wave is not measured anywhere

In this case the EWL circuitry is not working at all. Sometimes this can be fixed by restarting the software. If this doesn't fix the issue, the EWL isn't working anymore and the only solution is to replace the PCB. 

Case 3: the LED/EWL PCB gets burning hot

As the previous case, the EWL is not working anymore and has to be replaced.

I hope this helps. If something is not clear enough please feel free to ask questions. 

Thank you

Federico


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