So you managed to round up some clots to support your *cause* did you. You can't *have* watts without it involving resistance you ignorant bugger ! No resistance = no watts. Period. Then apply the VIR triangle to resolve the equations in different units.
I'm sorry you're all *WRONG*. End of discussion.
Graham
I suspect he meant Peak Music Power. < dives for cover >
Graham
Yes, I know, Jim. But you happen to be one of the few kind souls left who still saves your pdf files in Acro 3 compatible format. So guess what? I read every one I can get my hands on:)
Mike Monett
Nah. Still on topic. dB, don'cha know:)
Mike Monett
the
your
That 10nA is a sleep mode common input current. The A/D input current balancing circuit will force IN(+) and IN(-) cm currents to zero when Vin,cm is fixed at Vref,cm=Vref/2. This makes sense for a passive sensor that derives its stimulus from Vref. It makes no sense in a voltmeter application. If the input source impedances are not balanced in the varying input cm case, you are in even worse trouble- the LTC cannot handle very high source impedance in that case. The there is the LTC1152 buffer with typical CMRR of 130dB and Ib of
10pA. There may be a slight clock noise problem with it.
I don't know how it's even possible to make a measurement dependent on such a low current. It seems you could detect someone throwing a light switch in China.
Hmmmm....
When I attended this course in 'Electronics for Musical Instrument Technology' I already had much practical and indeed self-taught theroetical knowledge about electronics.
Our electronics lecturer had a PhD but actually his PhD was in acoustics. He made dumb statements about electronics from time to time. Drawing on the excellent education I had at my 'high school' - one of the oldest schools in the world...
I debated these issues with him and in no time at all we had developed a double-act where I'd give him the wink when he was straying into territory he didn't fully understand. To his eternal credit he didn't mind this and simply invited me to afford the class my knowledge in the area in question.
Sadly the same couldn't be said of the lecturers at University College London where I wasted an entire year being fed trash. Considering that UCL is meant to be one of the best academic institutions in the whole of the UK this was disappointing to say the least !
Graham
Now you have started me on a very interesting quest, to find out when the definition of the decibel changed - if it actually ever did.
It appears that the decibel originated in line telephony in 1923 when AT&T introduced the "Transmission Unit". By 1924 it was agreed to standardise on the "Bel" (10 TUs) and the "Neper", based on Naperian logarithms. By 1929 the TU had been renamed the "Decibel" and was firmly established as the unit of gain or attenuation.
All these units were defined as power ratios but could be used to describe related quantities such as current and voltage if the impedance levels were specified.
I have found a number of reference sources (listed below in order of first publication date) and all of them unequivocally define the decibel as a power ratio except the one I have named xxx (to spare any embarrassment).
1931 The Admiralty Handbook of Wireless Telegraphy (HMSO) 1934 Radio Designer's Handbook (Langford-Smith) 1936 Foundations of Wireless (Scroggie) 1938 Radio Communication Handbook (RSGB) 1956 Programme Operations Handbook (BBC) 1960 A to Z in Audio (Briggs)1972 Woods Practical Guide to Noise Control (Woods Acoustics)
1980 xxx2003 The Decibel Revisited (AES)
If you search on the Web, you will find a bewildering variety of so-called definitions for the dB, many relating to absolute sound levels, which I am sure the majority of knowlegeable people would agree are utterly wrong. (OK, I found the AES definition on the web too; but I like to think that they, of all people, should know what they are talking about)
The decibel does not appear to me to have been formally re-defined at any time since its inception - and its informal abuse by large numbers of ignorant punters does not alter that fact.
-- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk
Interesting. I went to St Edmunds College in Hertfordshire (Nr Ware) - we had a radio club that afforded us the opportunity to strip down bits of equipment and even to try to get some of it to work.
Later, I worked at Imperial College and attended some lectures there. (On computing - including digital electronics) I was pretty impressed by the standard.
Technology'
about
to
a radio club that afforded us the opportunity to
standard.
I've heard ICL was much better at electronics than UCL. Didn't stop UCL having a big head about their reputation though. 600 of us were invited to a series of 'last interviews', being told in no uncertain terms that the jolly 100 who passed were to consider themselves damn lucky !
The biggest con I've come across ever.
Graham
Is that the only holy approved *power* dB ? How much power can a LTC1152 take anyway ? ;-)
< ducks >Don't you think this deserves a new thread ?
Graham
The cosmic ray flux is surprisingly high. Cosmic rays are bad news. We're now learning that they play an important role in starting lightning stikes. Mind-boggling stuff.
Lead shields around the semiconductor, low-radioactivity lead (my Keithley 642 electrometer's remote heads are heavy beasts). Reduce the sensor's active area. Go down into a deep mine.
--
Thanks,
- Win
When I was "playing" with a Burr Brown ACF2101 and a Hamamatsu detector and data logging for days, I'd note events on the order of 30 seconds to 4 minutes where there would be between 1000 and 10000 electrons integrated as a burst. The detector was a 1cm sq device. This neatly matched some information I got from an observatory in France (located 3000m above sea level) where they had "calibrated" particle events for silicon detectors and provided data for both their elevation and also for sea level (which is where I was at.) So I took in some autunite I had and was able to produce these events at much higher rates by bringing it nearby. Also, there was a difference in both frequency and in pulse height (number of electrons stripped up) depending on whether or not the crystal of autunite I used was "on edge" or "on face" with the Hamamatsu detector diode. (I used the Burr Brown demonstration board set in this case and placed the entire system in a sealed container placed in a water/ice bath to maintain a stable temperature over the days of data logging.)
How do you deal with this in measuring instruments?
Jon
Oh, yeah? How about low-radioactivity lead shields (less than 15 self-generated alpha pulses per hour). RF shields, triple-turn long-path light shields, tree-configuration grounding, magnetic shielding, low-humidity control, dessicant paper with an inspection viewing port, dust control, adjustable feedback damping. Guarded shields to reduce measuring-node capacitance, noise-filtered guard signals. Radial mounting of the relevant components (zero-check, feedback resistors, damping capacitors, protection elements, etc.), about the input sensor. Temperature sensors, MOSFET offset-voltage temperature correction. Optically-polished sapphire insulators. Avoid charge-injection into insulators, dielectric absorption, wait for 24 hours before making measurements near the maximum specified sensitivity, especially after overload events (this includes turning on the instrument or connecting a signal, which should always be done with the zero-check activated). Remote head, input tube. Guarded feedback network. Zero-check hop compensation. Sapphire-insulated MOSFET card, protection diode. DO NOT TOUCH.
Integrated charge measurements, columbic leakage-current correction plots. Feedback-damping-optimized settling time. Zero-check and Alpha-ionization-event corrections. Input slide cover. Mainframe earth grounding system. AC-line-isolated battery-powered operation.
--
Thanks,
- Win
What do you mean by "order of magnitude"?
On 26 Jun 2005 20:06:10 -0700, Winfield Hill wrote in Msg.
Hey, Win, have you gone into the high-end audio marketing business? Almost sounds like it.
robert
No. It was not trolling garbage. I was being careful about the sign that results from decibel calculations.
The Bel was defined as a Unit of Attenuation, as applied to telephone lines and related apparatus. The original use of Pin/Pout gave a positive sign for a loss and a negative sign for a gain.
Being pedantic may not seem important to you but it is vital on large systems which consist of chains of elements, (from a wide range of mfrs) each with their own loss or gain. Since the overall performance of the system is obtained by adding all the 'dB's', then consistency in definition is important.
This would apply to telephone systems, rf amplifier chains (amplifiers, attenuators, cables, aerials) and even (say) laser optical chains.
Note that in all the above examples it is also important to be scrupulous in the use of the dB as a power ratio only.
-- Tony Williams.
On 6/27/05 2:29 AM, in article YFPve.32266$ snipped-for-privacy@fe3.news.blueyonder.co.uk, "Kevin Aylward" wrote, in part:
Some days you do show you are capable of a little humor. Good show.
Don
It did, in just the same way as your "bad" dude, maans your good.
None of this power stuff means *anything* today. Its simply irrelevant what book, committee etc attempt to define dbs. The dB is still a general term that is universally used as a means of expressing the log of a ratio. As I said, that's it. Period. No amount of discussion is going to change the way dBs (or db) are used as a general term. Its been redifined by common usage. No one has the bloody right to claim that their definition is the "correct" one.
There is simply no bloody law that says Bell labs original definitions mean anything at all. "I don't need to stinking Bell labs" to tell me what is a correct definition. Today, Bell labs are wrong.
Kevin Aylward snipped-for-privacy@anasoft.co.uk
[...]
Not the same 'He'. The author of the talk did not write the webpage.
That looks like sloppy journalism and doesn't engender confidence, but the main thrust of the talk seems clear enough.
It is one of my pet grouses that the reference levels often aren't clearly stated, so they leave the absolute values of related levels open to question. Manufacturers' specification sheets can be particulatly infuriating in this respect.
It would be interesting to see what that says about the subject, perhaps someone who has a copy could help us out with the relevant quotation?
-- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk
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