possible to "tune" a resonator?

background
I have a number of clone 'duinos mostly with resonators
I also have a Seeeduino with a crystal
the Seeeduino runs a little faster than the clones
I tried a scope on the X1 and X2 pins, but it simply froze the Seeeduino
continued when i removed the probe (not reset, just continued!)

the clones all seem to run at the same speed
I put a scope on the X1 and X2 pins of the clones with resonators
frequency on each of them seems to be < 16 MHz
I am aware that I might be loading the resonator, therby altering it's frequency

which leads me to my question
is it possible to alter the frequency of a resonator, or, like a crystal, it is substantially fixed?

thanks for listening

By playing with the values of the capacitors you can alter the frequency of the crystal circuit. You can't make large changes, but you can "trim" it if more accuracy is needed.

which leads me to my question
is it possible to alter the frequency of a resonator, or, like a crystal, it is substantially fixed?

Well even a crystal's frequency can be changed ( a little) by changing the values of the external padding capacitors. A 3 terminal ceramic resonators have their padding caps built into it's package, but I suspect you might be able to lower (but not raise) the frequency a little by adding extra external padding capacitors.

As far a using a scope on the crystal pins, unless you use a special (and expensive) FET type scope probe you will always have an effect on the frequency just by trying to measure it with a scope probe, more so on the clock in pin Vs clock out pin possibly.

Lefty

retrolefty:
As far a using a scope on the crystal pins, unless you use a special (and expensive) FET type scope probe

I did some research on such probes - yikes is all I can say. However, I did run across something interesting:

Apparently, in chapter 2 of Bob Pease's (RIP) book, "Troubleshooting Analog Circuits", there is a design for an inexpensive "probe" (see this post: Re: [EE]: Oscilloscope recommendation? by Jack Smith .).

I don't know if those specs given mean anything to -this- application, but if it would work, for $5.00 (and the cost of the book if you don't own a copy - I sorely need to pick one up) - it might be worth playing with at least...

:slight_smile:

crikey there's a lot of expensive kit out there!

Or, set the CKOUT fuse bit to provide a buffered clock output on the CLKO pin, and measure that.