See the 16mHz Arduino Mega crystal on an oscilloscope. A Tektronics Active FET probe with 1.5pF loading is used to examine the oscillator of the Arduino Mega.

3 Comments

1. 

   Dornado

   March 31, 2011 at 3:36 am

   I remember probing my Arduino Duemilanove with my eBay probes on an HP54601B 100Mhz scope and seeing the 16Mhz signal. I must be lucky or something.

2. 

   Jim Narem

   March 31, 2011 at 2:38 pm

   Input loading on a standard 100mhz chinese probe is 16 to 20pF.
   That’s around the size of the pair of caps on the crystal and the
   clock driver is pretty robust. I looked at an atmega324p with
   a 20mhz crystal using a crap 10X probe and got a perfectly good
   sine wave on both XTAL1/XTAL2 pins. A FET probe is overkill
   for this application.

   Note that there is a "low power/full swing" clock option on the
   clock driver. Using the "low power" setting may not drive the
   crystal hard enough to tolerate the probe load and will cause
   other problems in the real (noisy) world.

3. 

   unammused

   March 31, 2011 at 3:42 pm

   This can also be done with a number of simple FET circuits, no need to go out an buy an expensive probe.

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