Crystal testing issues

Status
Not open for further replies.
M

Murugesh_89

Full Member level 5
Joined
Nov 23, 2012
Messages
266
Helped
7
Reputation
12
Reaction score
6
Trophy points
1,298
Location
India
Visit site
Activity points
3,267
Hi,
I am using a 10Mhz crystal for my PIC microcontroller. Every thing including timer,uart are working fine. But i just want to test the output frequency of crystal using oscilloscope. The scope showing a sine wave with the time period of 1 milli seconds which leads to a frequency of 1000 Hz. Why it showing like this?



Thanks,
Murugesh
 

Assuming your oscilloscope has wide enough bandwidth to see 10MHz, the most likely reason is the scope probe capacitance is stopping the oscillator running properly. Remember that the loading capacitors around the crystal are very small in value and the probes themselves probably have much higher capacitance and appear in parallel with the real ones. If possible only measure at the output side of the oscillator as it will be less prone to loading than the input side.

If you really need to measure the frequency accurately, use a low-capacitance scope probe, preferably in x10 mode if it has it.

Brian.
 
Hi,

If your scope cannot handle that high a frequency, then make a simple program that toggles a port of the pic at a lower speed, say 1mhz, and then measure that on the scope and multiply its result by 10
 

Status
Not open for further replies.

Similar threads

Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…