Timeline for Why does my crystal oscillator spike so much?
Current License: CC BY-SA 3.0
12 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| May 6, 2014 at 0:54 | answer | added | Marla | timeline score: 2 | |
| Apr 6, 2014 at 14:05 | history | tweeted | twitter.com/#!/StackElectronix/status/452809206664810496 | ||
| Mar 15, 2014 at 20:26 | comment | added | user16497 | Did you compensate your probe? Untuned or uncompensated probes can overshoot like that. | |
| Mar 15, 2014 at 13:15 | comment | added | user16324 | You can accept one answer and upvote others if you like. | |
| Mar 15, 2014 at 6:12 | comment | added | cbmeeks | Agreed! Awesome comments. Both are excellent. Too bad I can't award credit to both as great answers. | |
| Mar 15, 2014 at 4:19 | comment | added | DuckTyped | @crasic and ConnorWolf your comments look like good answers to me, go ahead and earn those rep points! | |
| Mar 15, 2014 at 4:06 | comment | added | crasic | The frequency is jumping for two reasons, the excess ringing can mistrigger the frequency counter on the scope, so you have a measurement error. Otherwise all clocks have some amount of jitter (how accurately they keep their frequency), different crystals have different amount of jitter (like resistor tolerance, it depends on the component product line). Temperature fluctuations also cause the frequency to shift (clock drift). | |
| Mar 15, 2014 at 4:00 | comment | added | crasic | For various physical reasons (the primary one being that its impossible to achieve true "instantaneous" voltage jumping), all square wave generators will have some overshoot, the mathematical reason behind this is that a square wave is actually an infinite series of increasing frequency sine waves, since inductive/capacitative effects are frequency dependent, it affects different frequency components of the square wave differently, shunting of high-f components (no/well-damped fast ringing), and exaggerated overshoot usually indicates stray inductance, as Connor suggested. | |
| Mar 15, 2014 at 3:51 | history | edited | JYelton | CC BY-SA 3.0 |
Removed unnecessary thanks. Show thanks by upvoting and accepting answers.
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| Mar 15, 2014 at 0:34 | comment | added | Connor Wolf | If your scope probe came with a little metal spring thing that fits over the tip of the probe, try using that for grounding. The lower ground inductance should somewhat ameliorate the overshoot. Here is a question that covers the little ground thing: electronics.stackexchange.com/questions/40420/… . | |
| Mar 15, 2014 at 0:32 | comment | added | Connor Wolf | It's spiking because of the inductance of the ground-clip. | |
| Mar 15, 2014 at 0:11 | history | asked | cbmeeks | CC BY-SA 3.0 |