No, the test person just has to flip the switches in the classic SAR manner while observing an oscilloscope to see the phase shift. The algorithm is simple: flip a switch and if it doesn't go under-resonant, leave it on. Move on to the next switch. Once it's tuned, we don't care about the switch pattern.
-- 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
Without going into complete detail for a solution, didn't Larkin say he needs to give back answers as to what's going on using DSP?
Good grief, this is 107kHz can't you 'move' everything up stream? Simulate the LC in digital format, look at what's going on, and thereby give back the answer already in digital format? The tuning would be spot on, as long as you're working with a 32 bit ADC, you're better than DSP that goes back
16-18 bits, even 22 bits. Sounds like this is some type of 'analog computer' anyway.
How about a pitot tube and a MEMS differential pressure sensor?
On a sunny day (Thu, 21 Nov 2013 08:37:38 -0700) it happened RobertMacy wrote in :
Yes, I even have a pitot tube like device with digital readout sort of thing, Sensor is just a pressure chip (dunno what is in it). But is has no interface (well now we can read seven segment LCDs LOL).
But I am very much interested in the acoustic solution, extremely light and reliable. Pitot tubes suck (no pun intended) and many plane crashes are possibly related to it (ice forming).
I was thinking maybe, apart from detecting sidewinds, I can just have 2 piezo sensors, on in front, and one a bit more backwards, these come in water proof and are very small. But it is not a real project yet, thermal sensor would work too here. And I do not need extreme precision, a few percent would do.
The problem isn't simulating a transducer, i.e. doing numerical modelling. He's making a _simulated_transducer_, i.e. something that the customer's gizmo can drive as though it were the real transducer, but that, instead of transducing, produces data about the customer's drive/signal conditioning subsystem. So the simplest way to proceed is with a real LC with some data acq stuff hung on it.
Of course it's taken the August SED Brain Trust a week to talk it over. ;)
Cheers
Phil Hobbs
Turkey Countdown: T-7 days and counting
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 USA +1 845 480 2058 hobbs at electrooptical dot net http://electrooptical.net
Not quite 2:1 tries to avoid tolerances causing blind spots. Still may not succeed. ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
We built an air velocity sensor with a TO-92 transistor. At constant Ic, we vary Vc and observe Vbe, which lets us compute thermal resistance Theta-ja and estimate air flow. Works fine, but might dissipate too much power for your use.
-- 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
Over 200 posts so far!
The rules seems to be, the simpler the circuit, the more people have opinions about it.
Oh well, somebody has to keep SED alive.
-- 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
-- And you compensated for ambient air temperature, pressure, and humidity, how???
We have a nearby temperature sensor, but I don't think we needed to factor that in. I'll ask the guy who did the final algorithm in C. Theta-ja is measured independent of ambient temperature.
We're measuring air flow across a VXI module in a fan-cooled crate. We really care about cooling our electronics and detecting fan failure or blockage. Pressure and humidity won't change that much and, if it does, we *don't* want to correct for them, since our bottom line is the cooling effectiveness of the fans.
What we're really measuring is Theta-ja, which correlates highly but not exactly to air flow. We report temperature and "air flow" to the users, in VXI registers. In our tests, our air flow measurements correlate pretty well against an air flow meter. Air flow inside equipment is horrible to measure, since is varies all over the place at different locations.
-- 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
On a sunny day (Thu, 21 Nov 2013 10:56:06 -0500) it happened Phil Hobbs wrote in :
You mean real transducer, with controlled applied load.
World on its head, and NEVER 100% right,
Hey, how long have you been .. about IR, cannot even see it ;-)
-- Larkin's trolling. Notice how at first - with a +/-10% inductance - it was just four caps and a 4 bit dipswitch to get to within 1% of 107kHz? Then it was an unswitched cap flanked by with four switched caps, and now it's 6 or 8 switched caps. Seems he just keeps adding epicycles... What I'd like to see would be the values of the caps needed to tune 82µH to within 1% of 107kHz, the coil being +/- 10% of the nominal 82µH and the caps all being +/- 5%. Oh, and another issue which he seems to be skirting, the spec on the series resistance of the L.
It so already done: go to
-- -T.
Hmmm, I'd have to think about it more. I guess if you only want 'a' solution and not 'the optimal*' solution then it's OK.
George H.
*optimal being closest to resonance given the various components. Just thinking out loud... but it seems like there could very well be more than one 'near optimal' solution. And your search can only find one... which is perhaps 'good enough'.On a sunny day (Thu, 21 Nov 2013 10:56:06 -0500) it happened Phil Hobbs wrote in :
You mean real transducer, with controlled applied load.
PS and then WHY an LC????? If you want to simulate that a [power]opamp output should do.
He should know that, so maybe he is _not_ 'simulating a transductor'?
Maybe 'the custardcomer is always right' was not edible.
On a sunny day (Thu, 21 Nov 2013 18:56:21 +0200) it happened Tauno Voipio wrote in :
Yes.
I gave these links earier on in the thread:
Acoustic:
Or the less detail in the question.
If you had posted a complete spec and a longer description of the problem, a lot of people will decide they can't be bothered with it. And you would be getting the "I could do it at my hourly rate" posts.
-- John Devereux
-- Since theta j-a specifies the thermal resitance between the junction and the ambient temperature, the junction temperature for a given power dissipation can't be known unless the ambient temperature is also known.
I stated the problem clearly: I have an LC that I need to tune to resonance at a given frequency. A lot of people said, in effect, that I don't actually need an LC circuit. But I really do.
As far as "hourly rate" goes, for several "experts" here, their hiurly rate is zero, apparently by choice.
-- 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
Bloviation after bloviation... what we've come to expect from Larkin.
I sometimes suspect these "projects" are just fictions so that he can keep his name up on this group constantly.... typical behavior for a manic/depressive. ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
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