# How to look at Rubidium frequency standard using the oscilloscope?

I have the Rubidium frequency standard: http://www.thinksrs.com/products/PRS10.htm

and the Oscilloscope: https://www.atecorp.com/products/tektronix/tds3034

From the Oscilloscope, I want to look at 1PPS and 10MHz from the Rubidium frequency standard, How to do that?

Thank you very much.

From the Oscilloscope, I want to check 1PPS and 10MHz from the Rubidium frequency standard, How to do that?

Not at all.

Accuracy: 200 ppm

That's relatively bad, even for cheap measurement equipment.

From the rubidium oscillator's datasheet:

Accuracy at shipping: $\pm 5 \cdot 10^{-11}$

which is

$$\frac{2\cdot 10^{-4}}{5\cdot 10^{-11}}\,$$

i.e. 4 Million times more accurate than your oscilloscope promises to be.

I'd very much expect a comparable difference in oscillator phase noise.

In other words: your rubidium clock is so much better than your oscilloscope that you can only measure your oscilloscope by observing the rubidium clock, not the other way around.

Generally, you'll have a hard time finding an oscillator that beats your rubidium clock in accuracy, so that you can asses it. You can compare long-term against a good GPS-disciplined oscillator, or against other, more expensive atomic clocks.

• Thanks for quick response, but I would like to know a little more about rubidium clock, how to observe the rubidium clock? – Nate Duong Apr 17 '17 at 14:48
• what do you mean, "observe"? – Marcus Müller Apr 17 '17 at 14:49
• I want to see microsecond variation, is it vary? how much is it vary? How much differences there from PPS output to rubidium clock? Microsecond in variation I should be able to see if I were change this scope trigger on 1 of these PPS output and then I look at the others. And since system is 300MHz bandwidth and I can see of the other of 3 nanoseconds of variation, so microsecond variation in a few, if I trigger on 1 and watch the other, what does it do? That is my goal to check Rubidium frequency standard using the oscilloscope – Nate Duong Apr 17 '17 at 14:51
• read my answer. You can not use your oscilloscope to verify something that is 4 million times better than your oscilloscope. That's like using a scale designed to weigh elephants to verify the weight of a single dust particle. The whole point of having a frequency standard is to calibrate the rest of your equipment. – Marcus Müller Apr 17 '17 at 14:55
• I repeat myself: You can not check your rubidium clock with your oscilloscope. That'd be like trying to check the diameter of a single hair by putting it next to a cricket field. Seriously. – Marcus Müller Apr 17 '17 at 15:00

but I just want to check this rubidium are still working or not because once we dropped it on the floo

Short Rant:

OK. we have a sixteen messages conversation under my answer after you wrote a question, and only four full days after asking, it occurs to you that oops I dropped my multi-thousand-dollar frequency standard might be a relevant piece of info???

So, this is clearly no signal processing problem. You might have ruined a piece of equipment that someone else might rely on with their PhD or job. Find someone who's actually competent enough to diagnose the device, if in doubt, call the company that produced it. They have calibration services, and will be able to do that properly.

A "possibly broken", "checked only by a so-and-so competent" measurement standard is worse than not having a measurement standard; it might ruin future research. It's mandatory you inform the person in charge of the lab, and clearly mark the device as being of unknown state of functionality.