Tuesday, December 25, 2012

DSO Nano AC & DC Coupling Adapter to Shielded Banana

Merry Christmas!

I love the DSO Nano. It is perfect for so many quick uses. You never need an isolation transformer. It works fine in the field because it is so portable. Rechargeable batteries via standard USB. The list goes on and on...

Two issues with the DSO:

  1. It does not have AC coupling
  2. It does not have 4mm banana sockets
Both of these are solved with a little adapter I built.

 I have so many great leads, probes, clamps, etc... I really needed a way to connect them to this scope.

The circuit is about as simple as it gets. The black socket connects directly to the shield of the 3.5mm plug. The red socket connects to the tip of the 3.5mm shield with a switch in between. Across the switch is a 100nF capacitor. I found the size by looking at the schematics of a fluke portable oscilloscope.

  • Switch closed: there is a direct connection (capacitor shorted) from the tip to the red probe. 
  • Switch open: the capacitor is connected between the tip and the red probe.
I didn't have a mono 3.5mm cable laying around, so I just shorted together the unused side for some additional shielding. Buy the way, I know this isn't going to hold up to any sort of high frequency stuff, but then again, it is a DSO nano.

I used a small outlet box from Lowes. These things make great project boxes. They are inexpensive, durable, and easy to drill.

If you have a Nano, I highly recommend building one of these!