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- Опубликовано: 18 апр 2013
- A follow-up on another method to calibration adjust the Agilent 53131A frequency counter against the Stanford Research PRS10 rubidium standard.
The oscillator drift video: • EEVblog #61 - Crystal ...
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Наука
Thank you Dave for this video, I've learned more from this video and Mikes video on ipod nano reverse engineering than I have on many other videos on Oscilloscope uses!
Advice as an ex calibration tech ; the main characteristic is to identify the direction of the drift +ve or -ve and adjusting the oscillator at the outer extreme so when the one year calibration time expires the reference oscillator is at the other extreme within specifications. HP/Keysight/Agilent have very good application notes. also you need to apply Allan Variance. en.wikipedia.org/wiki/Allan_variance.
Of course, I said that. The whole point is to show people how to calibrate the internal osc, as they might only have temp access to a better oscillator.
Since you got that rubidium and distribution amps, you can just use that rubidium to provide all your scopes/counters/freq. generators a stable frequency standard, and maybe provide precise timing to your computers too.
Great as usual Dave...
Somebody already said but sticking the hex adjustment tool in a hex nut driver gives you a larger diameter to control the fine adjustment better. Because the metal driver is at the far end of the adjustment tool, it shouldn't affect the capacitance. That's why they are usually hex shaped I believe.
interesting info on the DTCXO. After 2 years there seems to be still very limited availability on it. Where a hobbyist as myself should go to acquire one to play around with in the US?
Hi Dave,
I'm glad that you tested the importance of the non-metallic screwdriver, but what about the tongue angle? You mentioned it, but didn't show how an incorrect tongue angle can ruin your calibration. That's a big trap for young players!
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You can do that with the waveform mode too. The Lissajous pattern has no inherent advantage in this case, it's just a different type of display. With the waveform you can have the scope stats measure and track the phase if needed.
I did but wrote the comment before the end. The advantage of Lissajous pattern is that you can track phase. One way or another it is almost impossible to keep the free running oscillator stable in a narrow margin of error, a case of an instrument with high resolution and high error.
Question.. Could you add another variable cap of far lower value. But the same number of turns to add a fine tune ability to this, or would it just add more % inacuracy and temp variation?
Precise enough for what exactly?
Superb
How can you measure how far it's off? Would be a great follow-up video.
I would bet that the plastic screwdriver is 'ESD' safe and is therefore somewhat conductive. That is why the freq changed when Dave inserted it to make the adjustment.
Any guesses?
Good question, I think it's possible to change that.
You may be right, or they are almost imposible to get now, there where loads of really nice enclosed ones in the old Bang and olefsens I used to play with when I was a young lad
Could you modify that tuning pod to be more stable and less sensitive by adding a small cap in parallel with it.
can you mod the unit so it has a fine tune pot too?
I remember you had eBay rubidium reference clock (if I am not mistaken). Would be interested to compare to this one.
Is using a direct coax cable from your frequency standard and from your frequency counter to your scope going to have a limit on the bandwidth of your measurements? I guess your not interested in amplitude, only frequency though.
Form previous video and this video I've noticed that oscillator is constantly increasing frequency. Why is it doing so? Is it common to all oscillators? Will it increase frequency forever, or will it at some point start to decrease it?
would fitting a new crystal with heatsinks attached to it make much difference ?
Is there a noticeable difference between the ceramic (White brittle) and plastic non-metallic (plastic) adjustment screwdrivers?
Dave, the best methode for this task using an oscilloscope is the so called Lissajous figure. It is fun, easy and accurate!
Reminds me of trying to tune a piano; one string is perfectly on, then you tune another one until it's perfect and the first string is a few Hz high, so you work on the first one again. Then you do that with the other 87 keys (or until your ears bleed, whichever comes first.)
I wish I had a good reason to buy some of this stuff, oh and the money would be good too. Do they not do one of those non metallic, non conductive things with a decent handle on?
Dave, if counter has external ref. in please try instrument with time standard you scored while ago form eBay. The one used in GSM base station.
Yes, you just buy the option. Or simply use an external one.
Your best bet is to use an external reference standard for calibration
Don't trust the internal oscillator
Thanks for a great video
could always slap in a sub-ppm tcxo circuit, would be a good upgrade without the cost of an ocxo, i wonder why they skimped so badly on something so important to a frequency counter, also wonder why the trim capacitor has such a huge range for adjustment, just makes it more difficult to adjust
can u unbox and reveiw the phiplips gogear conect 3 please
4:00 you need to use a nice long lever so you can "gear down" your movements :)
I know that this video is an old one, but maybe my advice can still be useful? To turn the screw much more precise, you can glue a i.e. 1 foot long non conducting pen at a 90 degree angle, so it looks like an angle screw ratchet.
In this way, you avoid to put your hands near the screw and if you hold in the far end of the pen, you han adjust with 1/1,000 degree if you want to.
Yeah you get the extra (15 digit) resolution only on the GPIB/RS232 output...
"My Rubidium", you have fallen in love already ;) What a fin whole bunch of good stuff in that boot fair, you lucky git :D
8 minutes? great!
Normal crystall oscillators do drift a lot due temperature differences. So it may well have been accurate enough on *some* temperature.
Ah.. Apparently I did miss that. Well, most of those intruments I've seen seem to have 10MHz ref input.
I figure that's what they were doing originally, which would be why the internal was so ludicrously out of cal.
Depends mostly on the temperatur
It really needs a vernier adjustment but that adds more expense and the drift may render any accurate adjustment purely academic.
I didnt know you could do 3D with 2 sine waves and a scope :P
Cant you just put one more low value cap in paralell? So that you can adjust that conveniently?
For a second I thought they were perfectly in sync, then I realised youtube was buffering... :D
I doubt a radio variable cap will have the same range as the one that is already there.
Dare I say....First... had to do it.
Great video as always.
that is good for Australia ...... :)
Atomic clock?
I think it would be easier if that adjustment tools had a bigger diameter as a grab handle.
Or, you could just use your rubidium oscillator as an external 10MHz reference for the Agilent counter and forget using the internal entirelly.
Ha! Mix the two signals and you have a Theremin!
almost 2 AM in germany...
time difference is a biatch...
You didn't watch the entire video did you?
You could surley get a better trim cap out of a decent old school radio, you can't even "hot snot" that one.
Yeah but now I have a half an hour to kill.jk
Love you Dave! Make the videos any length you like. People that don't have time can skip ahead, those that do will hopefully learn something extra.
That would defeat the purpose of the internal oscillator, wouldn't it? :P
They weren't going to use the internal oscillator anyway, so why pay extra.
He should have tried being less capacitive :D
you should have tried using gloves with the plastic piece
maybe software calibration would be smarter
yeah, but he hasn't lifted her skirts yet :(