You could probably do it if you could run a few coax or triax lines to the place of measurement, but that sounds.. challenging.
Best regards, Spehro Pefhany
-- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
I think they would flog me if I'd just mentioned that :-)
-- Regards, Joerg http://www.analogconsultants.com/
I think we can cover that part as well because one of the guys in our group is quite experienced in the production of really small stuff. Not an EE, but in the end an inductor is nothing else that a coil spring from an ME point of view.
-- Regards, Joerg http://www.analogconsultants.com/
isn't
cables.
The Boonton uses a phase-sensitive detector, at 100 KHz or 1MHz, and is immume to cable capacitance. But to do that sort of 3T c measurement, you'd need two coaxes, or n+1 if there are n caps to be measured.
Or TDR it.
-- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
Dremel it!
-- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
Sort of/not really, I'd say. Based on stripwound data, though. Typically what you see is really high inductance at low frequencies, peaking resistively in the 100kHz range, then falling after that. The impedance is still quite high in the 10MHz range, usually better than ferrite, but drops after that, where you'd need something like high frequency ferrite beads to take over.
Stripwound typically ends up partly shorted to itself, enough that ohmmeter probes read a few ohms to any point, within a layer or across layers. The impedance curve is basically due to eddy currents, so the impedance of a single layer, or a thin rod, should be higher in frequency than a bulk strip core is. The Q probably still isn't the greatest, but it'd be something to try.
Tim
-- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms
Ouch! Looks decidedly non-trivial.
Whatever you end up doing, beware of the temperature dependence of ferrites. Unless the temperatures involved are practically constant, getting the resonance of a ferrite-core inductor stable over temperature may prove a considerable headache.
Recently I've been bitten by this less-than-well-documented property of some no-name ferrite. Got a new, but rather inexpensive spectrum analyzer and found out that it would not track the signal of it's own built-in tracking generator. When turned on, set to 20 kHz RBW, and connected directly output-to-input it would see no steady signal, just wavy lines on the screen, resulting from slope demodulation of some PLL's loop ringing, the receiver's center frequency being way off-center from the TG. As it warmed up, ca. 20 minutes later, it would slowly drift into the frequency it's been adjusted for at the factory and show a stable signal for a while. After 1-2 hours, as it heated up even more, it would drift out of tolerance and the signal would slowly disappear into wavy lines again. At 400 kHz RBW however all would look well all the time.
The manufacturer from Shenzhen seemed to hardly understand the issue, and shipping the thing back looked like a lot of hassle and additional expenses, so I ended up repairing it instead. I found out that the receiver's third IF stage was done with LC filters, the Ls wound on some unknown ferrite core (all 6 Ls in the rather symmetrical filer being equal). The Cs were NPO and had sufficient stability, but the ferrites were really drifty, although all equal to each other (which fortunately made the whole filter drift equally in one direction and not spread).
In the end, I ended up replacing the local crystal oscillator that was driving the mixer of this stage with a wide tuning range (350 ppm) VCXO (plus a little amplification and filtering on the VCXO's output) and using an LM34 temperature sensor plus an opamp to control the VCXO's frequency. The LM34 was put into the drifty third stage module near one of the filters so it could track the temperature. After setting this up, running the spectrum analyzer throug some 5 or 6 temperature cycles and adjusting gain and offset of the newly-added 'compensation' as it went, I finally got it sufficiently stable. It ended up with a below 3-ish kHz drift over temperature as opposed to the manufacturer's originally specified 10 kHz and the actual measured 50 to 70 kHz drift when I first got it. A factor of 20, more or less, and no more wavy lines.
When I finally had a look at the service manual that they decided to send me after some waiting, and found there instructions to calibrate the center frequency after at least half an hour of operation, somehow I was no longer surprised. So much for ferrites and their more insidious propertied.
So, if you end up with a micro-miniature ferrite in your application, and need to track it's resonance frequency, make sure to design in some local temperature sensing, so you can correct out the nonlinearities later. If that's not possible, make sure to select and test the ferrite very well.
Sure, given your well-known profession, if it's a medical device that can take a more or less 36.6°C environment for granted, the above may not apply, it also won't apply if you are only interested in the changes of the frequency and can safely ignore the absolute value. Otherwise a ferrite-LC may go well with some compensation.
Regards Dimitrij Klingbeil
Realtime blood pressure measurement?
-- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
made
isn't
cables.
Running another cable is completely impossible in this app.
We could do that. But doing it in the frequency domain is probably easier and not so prone to nightmares at the EMC lab.
-- Regards, Joerg http://www.analogconsultants.com/
That's why there's engineers in the world :-)
Luckily this application sees an almost constant temperature, and one that is always the same. But slow drift would not hurt because we could calculate that out. And we'll have to because just the mere repositioning of the cable will cause drift. It is inevitavbly part of the resonant circuitry, at least to some extent.
Yikes! That looks like a design from Uncle Chen's Backyard Works.
I probably would have returned the whole thing. But I understand the urge, you are an engineer and it just has to be fixed. I am the same way sometimes.
The analyzer I bought last year is a Signalhound. It was something around $1600 including the tracking generator. It tracks beautifully and has to in my cases. For example, when you must check out crystal filter structures the track gen has to be in lockstep even when RBW is only a few Hertz. That's impossible with anything purely LC-based.
In this case I really don't have to worry about thermal drift. Only about size, plus the fact that mankind has to be able to produce this.
-- Regards, Joerg http://www.analogconsultants.com/
Wescott, I presume? :)
There's an awful lot of Tims (or Jims) and Williamses in this business... go figure!
Tim (not the filter guy) Williams
-- Deep Friar: a very philosophical monk. Website: http://www.seventransistorlabs.com/
Care to mention the maker? Atten?
Best regards, Spehro Pefhany
-- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
Well, if that's all you want, just take some 1/4" mylar recording tape and wrap it around the wire or form it into a spindle. You won't get much AL out of whatever mix is used for recording tape, but if you're lucky, it might be enough. It's certainly easier than making your own tiny rods.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...
Not French, but my favorite....
cheers
I wonder if there is a recording head that might be that small? Maybe a video head?
tm
Mmmm.. looks like it would be good with smoked porkchops (Kasseler) from our local Euro meats place.
Do you recommend with or w/o horseradish? Generally I'd probably prefer the latter.
Best regards, Spehro Pefhany
-- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
can you stick an oscilator in there? A 555 die is not going to fit, but perhaps there's something else that would.
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I prefer with horseradish. I don't think I ever tried it without. It has a nice Zing from the horseradish, but not over whelming. ;)
Cheers
Getting ferrite down to .004 may be a bridge too far. You may want to look at shaving off a sliver of .004 amorphous steel. For experimentation, you can find a piece in the anti theft tags of your next big box store purchase.
Kevin Gallimore
Yes. AT6011 of ca. 2010 make. Also rebranded SA6011T by MCP Shanghai. It looks like a newer version of the Hameg HM5011 with a wider sweep span range, and an LCD for the frequency and settings readout. Actually, given the HM5011 horrible datasheet performance (100 kHz frequency offset, and
150 kHz drift per hour), the Atten looks like a noticeable improvement, even when it's third stage is not compensated. I wonder, how the TG on the Hameg's "original" could even have worked at all. Maybe it never did or they've redefined "work" for 400 kHz RBW only. At least Atten used a TCXO and a DDS IC followed by a PLL for upscaling where Hameg originally had used a VCO with analog tuning and (as it seems) free-running without a frequency feedback at all, so at least Atten's first two IF stages and TG are stable.The AT6011's third IF stage is the only one not controlled by the central TCXO, so while everything else is in lockstep, this stage relies on LCs. In a pinch, it is fixable by way of a SI550BG32M1250DG (VCXO), LM35 (temp sensor) and some other minor supporting circuitry, if you happen to have one and need an idea how to make it behave properly.
That was 2010 however and they could have changed suppliers in the mean time. No telling, what ferrite is in there now. No idea if the correction would still work the same on newer models or if it would even be needed.
Given that re-use is popular in many places, chances are that this third IF stage module with its 32.125MHz quartz LO and string of filters switchable between 2 and 6 resonant LCs is also used in other models. The AT6011 is very modular after all, with a minimum of interconnects between the modules, so its design easily "invites" copying.
Regards Dimitrij Klingbeil
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