How The Fastest Measurement Device were Made? - Page 1
Forum section: electronics / projects

author: Mechatrommer
author_rank: Super Contributor
timestamp: June 14, 2011, 07:15:25 am
content: i just wonder. how the maker can confirm the performance of the measurement device they are making. do they need physicist to do that? or down to molecular inspection? maybe just a dumb question.32GHz Infiniium 90000 X-Series Oscilloscopes

author: scrat
author_rank: Frequent Contributor
timestamp: June 14, 2011, 08:59:09 am
content: The frontiers of measurement always made me wonder the same thing...

author: ejeffrey
author_rank: Super Contributor
timestamp: June 14, 2011, 09:22:08 am
content: Very carefullyThat said, there are plenty of sources in the 40 GHz range and even higher -- I know people who work on THz generation. Check out Miteq for a lot of components designed for satellite communications. I personally am an optics guy, and it is fairly easy to generate any frequency you want by the beat note of two lasers -- as long as you have a fast enough photodetector to measure it. Both Silicon and InGaAs detectors are available for a cost of a few thousand dollars that go up to 40 GHz or so.Another major difficulty is cabling, or more precisely connectors. As long as you keep the signal within your device in controlled impedance PCB traces or within rigid waveguides, things are not too bad. If you want to connect your signal to an oscilloscope through a flexible coax cable with mating connectors at both ends this are a lot more difficult. The slightest misalignment or defect in the connector can just trash your performance. Overtighten a microwave connector just once and you can cut its usable bandwidth in half. Undertighten and the dielectrics will not mate fully and there will be an impedance mismatch. At 32 GHz *everything* is a transmission line.

author: Mechatrommer
author_rank: Super Contributor
timestamp: June 14, 2011, 12:35:50 pm
content: any specific device/link reference to be used as calibrator? fiber optic device?

author: Unknown
author_rank: Unknown
timestamp: June 14, 2011, 11:50:36 pm
content: These are just their fastest real-time scopes, there have been sampling scopes with as much or more bandwidth available for a long time. Same for spectrum analyzers, with may be used to verify a sinusoidal signal for purity. Frequency can be measured with a frequency counter. Amplitude with a power meter. Both are available for well beyond 32GHz. Generators beyond 32GHz are also readily available. But if you're pushing the envelope in bandwidth, you're likely also going to have to push the envelope with regard to calibration / test equipment. I'm guessing this scope isn't supported by Fluke oscilloscope calibrators.If you read through the calibration procedure, you see that they mostly rely on self calibration, and use a DMM to verify DC gain, a 10MHz source to verify time base accuracy and a microwave signal generator and power meter for bandwidth verification.

author: Mechatrommer
author_rank: Super Contributor
timestamp: June 15, 2011, 07:37:29 am
content: Quote from: alm on June 14, 2011, 11:50:36 pmwhich in turn. divert the question. how they are going to confirm the performance of those devices? frequency counter, power meter, spectrum analyzer, generators etc?

author: ejeffrey
author_rank: Super Contributor
timestamp: June 15, 2011, 09:15:32 am
content: Quote from: Mechatrommer on June 15, 2011, 07:37:29 amFrequency counters are easy. They count cycles relative to some reference clock -- this could be a pre-calibrated oven controlled crystal oscillator or a rubidium standard if you want the utmost accuracy. As long as they work they are accurate to +/- 1 count. A spectrum analyzer will be as accurate as your synthesized local oscillator, which is measured with a frequency counter.The other major tool in frequency measurement is the essentially perfect sum/difference/harmonic generation in mixers. The simplest example is the frequency doubler. By symmetry, it must return to its original state after a complete period of the input signal. The only output waveforms that have this property are harmonics of the input. So if you send a frequency doubler a very stable sine wave, you get a signal out at exactly 2f with maybe some 3f, 4f, ... thrown in, but those are widely separated and easy to identify. You can use chains of frequency multiplers to generate an arbitrarily high frequency that is a precise multiple of some lower frequency, and as long as the circuit works you get the right frequency. Difference frequency generation is also perfect and simple if you have a reference frequency at f_0 and an unknown frequency f_0 + df and you feed the two signals to a mixer you get out a signal at exactly df which you can measure with a low frequency counter.Power meters are intrinsically wide bandwidth -- they measure the heat deposited in a terminating resistor and in principle they work from DC to daylight (literally -- shine a laser pointer on it and you can measure the power. That is 500 THz!), and their behavior is guaranteed by the laws of physics (conservation of energy).

author: ejeffrey
author_rank: Super Contributor
timestamp: June 15, 2011, 09:50:56 pm
content: Oh, and if you want to see some serious measurement porn, go look up optical frequency combs. By using the perfect sum- and difference-frequency generation by nonlinear optical materials people can measure the frequency of petahertz lasers to sub-Hz resolution. By locking such a laser to a transition in an aluminum ion, scientists have recently built an opticals clock with an uncertainty of around 10 millihertz. The actual absolute accuracy of the clock is much worse. The absolute error is dominated by uncertainty in the definition of a second which is currently based on a cesium standard that is not currently possible to measure as precisely. Instead, they demonstrate the quality of their clocks by building two and comparing how they drift relative to one another.

author: Hugoneus
author_rank: Frequent Contributor
timestamp: June 15, 2011, 10:43:16 pm
content: I have a lot of information about this particular topic, in fact my Ph.D. thesis was on mm-wave analog to digital converters. If there is still interest I can type out a paragraph about this...

author: Lawsen
author_rank: Frequent Contributor
timestamp: June 16, 2011, 01:20:29 am
content: The test for the fastest oscilloscope will need a repeatable faster event to confirm it. One application for fast oscilloscope is a branch of physical chemistry called kinetics. Kinetics measures the rate of chemical reactions. The indication of a chemical change will be indirect like a change in pH, conductivity, color, absorbance of light, or transducer output to the fast oscilloscope.Lawsen

author: Mechatrommer
author_rank: Super Contributor
timestamp: June 16, 2011, 01:58:20 am
content: Quote from: Hugoneus on June 15, 2011, 10:43:16 pmyes pls i will be interested! but pls dont put the whole text here, its a pain reading long article in a forum. just pls provide an attached file (doc, pdf) so in case it is too long for me, i can just print it out and read in hardcopy.

author: saturation
author_rank: Super Contributor
timestamp: June 16, 2011, 12:47:52 pm
content: A good way to find out is see what metrologists are doing, NIST.gov is very public about their activities.Electronics engineers are between physicists and technicians. The simplest description of EE used in academia is applied physics. At the cutting edge, you're more like a physicist, at the end user level, you are closer to a technologist. In most applications, they bridge the gap between the two.

author: Lawsen
author_rank: Frequent Contributor
timestamp: June 16, 2011, 04:47:48 pm
content: Extremely fast and repeatable event is found inside a RADAR at an airport or airplane. This is one application for Agilent's fastest measurement oscilloscope.http://cp.literature.agilent.com/litweb/pdf/5989-7575EN.pdfReally fast oscilloscopes might need a MASER, not light waves, but microwave stimulated emission radiation out of its cavity to an attenuator for measurement. The frequency can be verify by a fast frequency counter and the amplitude by a high frequency power meter or spectrum analyzer power versus frequency, where power is the dependent variable that depends upon frequency being adjusted by a knob to see changes in the power level as dependent variable.http://en.wikipedia.org/wiki/Maserhttp://www.symmetricom.com/products/frequency-references/active-hydrogen-maser/MHM-2010/http://en.wikipedia.org/wiki/Dependent_variableA hydrogen maser is a tool and source used to verify fast oscilloscopes. My thought is a fast and reproducible phenomenon in nature or technology are used to verify a fast oscilloscope. My fastest oscilloscope in my room is 50 MHz.Here is a good dream oscilloscope, but these are not fast, good enough for everyday experiences, not exotic masers and radar.http://www.home.agilent.com/agilent/product.jspx?nid=-33575.970747.00&cc=US&lc=engLawsen

author: Mechatrommer
author_rank: Super Contributor
timestamp: June 16, 2011, 11:56:56 pm
content: thanx lawsen and saturation for the info.

author: ArtemisGoldfish
author_rank: Regular Contributor
timestamp: June 20, 2011, 07:37:36 am
content: We have some 20GHz oscilloscopes at work, maybe I'll take a peek at how they're calibrated when the Tektronix people come to visit

author: Mechatrommer
author_rank: Super Contributor
timestamp: June 20, 2011, 05:22:06 pm
content: Quote from: ArtemisGoldfish on June 20, 2011, 07:37:36 amwill be a good idea!