Re: A stable and repeatable low value capacitance meter
David,
Arduino CPU pin impedance when configured as an analogue input is specified as 100MegOhms.? The charging source/sink is capable of 20mA and the measurement is a voltage ratio, essentially independent of the supply.? Quite interesting to do the sums for the sampling.? I agree that the thread is not easy to follow if you are in a hurry.
It was not the absolute accuracy but the stability and repeatability that surprised me, having assembled? the basic circuit on a prototyping board out of curiosity.? I realised it would be useful to me as a stand alone device for measuring/sorting SMD capacitors in the 2-1000pf range, and I would commend it on that basis.
PeterS???????? G8EZE
-----Original Message-----
From: Dr. David Kirkby, Kirkby Microwave Ltd <drkirkby@...>
To: [email protected]
Sent: Sat, 3 Sep 2022 13:12
Subject: Re: [Test Equipment Design & Construction] A stable and repeatable low value capacitance meter
A while ago I came across a really simple capacitance meter at ??
I am usually sceptical about claims for such designs, but this one does not drift or require constant re-zeroing when measuring capacitors of a few pF.?
I might have misunderstood it. The adverts on the page, PDF and circuit in separate files didn’t make for easy reading.?
For small capacitors, unless the DC voltage is very high little energy will be stored in the reference capacitor in a reasonable time. That would suggest to me that a very high impedance voltage measurement would be needed to measure the voltage capacitor due to the short T=Cref Rload time constant.?
I have probably misunderstood the design.??? ?
I recall a thread on the Keysight forum where a guy had bought a Keysight handheld LCR meter. He measured a capacitor, then compared the valve to that measured by a Fluke and other handheld multimeters. All the multimeters gave approximately the same value, but the LCR meter something significantly different. I suggested that this may be due to the different methods of measurement - the LCR meter using AC and (probably) a 4 terminal connection, and the DMMs charging/discharging a capacitor and measuring the time constant. I don’t know if that was the reason or not, but I do see significant differences between my handheld Tektronix DMM which hasn’t been calibrated for decades, and an HP 4284A Precision LCR meter which has been calibrated by Keysight - not some Mickey Mouse lab.?
Peter S ??? ??? G8EZE
Dave
--
Dr. David Kirkby, Kirkby Microwave Ltd, drkirkby@...Telephone 01621-680100./ +44 1621 680100 Registered in England & Wales, company number 08914892. Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom
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Re: Looking for an article out of an old QEX
Jeff, Tom and Jim,
Thank you. I didn't think about archive.org. Got it.
73,
Ray, W4BYG
On 9/3/2022 15:39, Jim Strohm wrote:
Ray,
While ARRL membership isn't for everybody, it does give you
access to all their periodical?publications.? I'm glad that
several years back I had enough money for a Life membership
... but only because it was heavily discounted.
I'd get a QCWA life membership but then seem to never
discount it.
Anyway, Jeff's link seems to give you exactly what you
need.
73
Jim N6OTQ
On Sat, Sep 3, 2022 at 1:31 PM
Ray, W4BYG < w4byg@...>
wrote:
I am looking for
the article "How to design wide-band RF
Quadrature Network" by G.W.Horn, I4MK
QEX, November 1982. Anyone still have such in their QEX
stash? Mine only goes back into the early 90's.
An electronic scan of the article would be appreciated.
Thanks for your attention.
Ray, W4BYG
--
"If you want to build a strong house, I'll give you my engineer's number.
If you want to build a strong life, I'll introduce you to my carpenter."
Lebron and Heather Lackey
--
"If you want to build a strong house, I'll give you my engineer's number.
If you want to build a strong life, I'll introduce you to my carpenter."
Lebron and Heather Lackey
|
Re: A stable and repeatable low value capacitance meter
An interesting article.
I've built the Roman Black C Meter, which drifts a couple of pF over a short time, and the van Dijk code change, which seemed like it took a couple of minutes before the correct reading appeared.
So a meter that doesn't drift and has fast cycle times is desirable, but one tied to a computer for readout is not useful and my brain is far too old to learn how to modify Arduino code to add a LCD display to make a portable unit. If someone does, please publish.
John
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Show quoted text
On 9/3/2022 1:29 AM, swallowp via groups.io wrote: A while ago I came across a really simple capacitance meter at
I am usually sceptical about claims for such designs, but this one does not drift or require constant re-zeroing when measuring capacitors of a few pF.? It puts the DUT and a reference capacitor in series, applies a DC step voltage and measures the resulting voltage across the reference capacitor.? A? disadvantage is that the DUT is floating, the reference capacitor being the input capacitance of the Arduino.? The article is the start of a thread which has links to notes on resolution and expanding the measuring range.
The original scheme uses a PC to display the results, but it is fairly trivial to add an LCD or OLED to make a small self contained bench meter using an Arduino Pro-Mini module or similar - example attached.? Ditto to add an offset calibration mode to compensate for different test lead capacitances.
I have tried a number of capacitance meter circuits over the years and tested several devices of the AADE/LC100 self-oscillating type, which although they use sound principles and theoretically offer good accuracy, in practice suffer from drift when measuring small values of capacitance (and sometimes huge errors when measuring larger capacitors).? This circuit is both sensitive and stable, even on the plugboard I used to try it out.
Peter S ??? ??? G8EZE
|
Re: Looking for an article out of an old QEX
Ray,
While ARRL membership isn't for everybody, it does give you access to all their periodical?publications.? I'm glad that several years back I had enough money for a Life membership ... but only because it was heavily discounted.
I'd get a QCWA life membership but then seem to never discount it.
Anyway, Jeff's link seems to give you exactly what you need.
73 Jim N6OTQ
On Sat, Sep 3, 2022 at 1:31 PM Ray, W4BYG < w4byg@...> wrote:
I am looking for the article "How
to design wide-band RF Quadrature Network" by G.W.Horn, I4MK
QEX, November 1982. Anyone still have such in their QEX stash? Mine
only goes back into the early 90's.
An electronic scan of the article would be appreciated.
Thanks for your attention.
Ray, W4BYG
--
"If you want to build a strong house, I'll give you my engineer's number.
If you want to build a strong life, I'll introduce you to my carpenter."
Lebron and Heather Lackey
|
Looking for an article out of an old QEX
I am looking for the article "How
to design wide-band RF Quadrature Network" by G.W.Horn, I4MK
QEX, November 1982. Anyone still have such in their QEX stash? Mine
only goes back into the early 90's.
An electronic scan of the article would be appreciated.
Thanks for your attention.
Ray, W4BYG
--
"If you want to build a strong house, I'll give you my engineer's number.
If you want to build a strong life, I'll introduce you to my carpenter."
Lebron and Heather Lackey
|
Hi David, On 9/2/22 7:29 AM, Dr. David Kirkby, Kirkby Microwave Ltd wrote: I am personally interested in doing this in a low impedance circuit.
That probably means having a transformer with a single turn on the
secondary. A bit of nichrome wire as the secondary would be convenient
if it could be the current sense too. Using an Injection Transformer, as in HP4342 Q Meter, uses known Power or voltage applied to a Constant Voltage Injection System. An example Injection Transformer Fixture shown in: Section "Injection Transformer Q Measurement" Using an Oscilloscope for voltage measurement. As mentioned before, Oscilloscopes do not make highly accurate voltage meters. A simSmith model is included in web page, a way to measuring the measurement. Note applied Q, 200 in the case, does not match measured Q, 196.7. Required is a 10 Mohm voltmeter. As used in HP 4342A. Though an Injection Transformer fixture, with oscilloscope, could be valuable for evaluating differences between inductors. As described in HP 4342A documentation, there are internal errors which are accounted for. 4342A calibration procedure includes many calibration adjustments. John KN5L
|
Re: A stable and repeatable low value capacitance meter
A while ago I came across a really simple capacitance meter at ??
I am usually sceptical about claims for such designs, but this one does not drift or require constant re-zeroing when measuring capacitors of a few pF.?
I might have misunderstood it. The adverts on the page, PDF and circuit in separate files didn’t make for easy reading.?
For small capacitors, unless the DC voltage is very high little energy will be stored in the reference capacitor in a reasonable time. That would suggest to me that a very high impedance voltage measurement would be needed to measure the voltage capacitor due to the short T=Cref Rload time constant.?
I have probably misunderstood the design.??? ?
I recall a thread on the Keysight forum where a guy had bought a Keysight handheld LCR meter. He measured a capacitor, then compared the valve to that measured by a Fluke and other handheld multimeters. All the multimeters gave approximately the same value, but the LCR meter something significantly different. I suggested that this may be due to the different methods of measurement - the LCR meter using AC and (probably) a 4 terminal connection, and the DMMs charging/discharging a capacitor and measuring the time constant. I don’t know if that was the reason or not, but I do see significant differences between my handheld Tektronix DMM which hasn’t been calibrated for decades, and an HP 4284A Precision LCR meter which has been calibrated by Keysight - not some Mickey Mouse lab.?
Peter S ??? ??? G8EZE
Dave
-- Dr. David Kirkby, Kirkby Microwave Ltd, drkirkby@...Telephone 01621-680100./ +44 1621 680100 Registered in England & Wales, company number 08914892. Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom
|
Re: A stable and repeatable low value capacitance meter
The example .pdf went AWOL on the first pass!
PeterS???????????? G8EZE
-----Original Message-----
From: swallowp via groups.io <swallowp@...>
To: [email protected]
Sent: Sat, 3 Sep 2022 9:29
Subject: [Test Equipment Design & Construction] A stable and repeatable low value capacitance meter
A while ago I came across a really simple capacitance meter at ?? https://wordpress.codewrite.co.uk/pic/2014/01/21/cap-meter-with-arduino-uno/index.html
I am usually sceptical about claims for such designs, but this one does not drift or require constant re-zeroing when measuring capacitors of a few pF.? It puts the DUT and a reference capacitor in series, applies a DC step voltage and measures the resulting voltage across the reference capacitor.? A? disadvantage is that the DUT is floating, the reference capacitor being the input capacitance of the Arduino.? The article is the start of a thread which has links to notes on resolution and expanding the measuring range.
The original scheme uses a PC to display the results, but it is fairly trivial to add an LCD or OLED to make a small self contained bench meter using an Arduino Pro-Mini module or similar - example attached.? Ditto to add an offset calibration mode to compensate for different test lead capacitances.
I have tried a number of capacitance meter circuits over the years and tested several devices of the AADE/LC100 self-oscillating type, which although they use sound principles and theoretically offer good accuracy, in practice suffer from drift when measuring small values of capacitance (and sometimes huge errors when measuring larger capacitors).? This circuit is both sensitive and stable, even on the plugboard I used to try it out.
Peter S ??? ??? G8EZE
|
A stable and repeatable low value capacitance meter
A while ago I came across a really simple capacitance meter at ?? https://wordpress.codewrite.co.uk/pic/2014/01/21/cap-meter-with-arduino-uno/index.html
I am usually sceptical about claims for such designs, but this one does not drift or require constant re-zeroing when measuring capacitors of a few pF.? It puts the DUT and a reference capacitor in series, applies a DC step voltage and measures the resulting voltage across the reference capacitor.? A? disadvantage is that the DUT is floating, the reference capacitor being the input capacitance of the Arduino.? The article is the start of a thread which has links to notes on resolution and expanding the measuring range.
The original scheme uses a PC to display the results, but it is fairly trivial to add an LCD or OLED to make a small self contained bench meter using an Arduino Pro-Mini module or similar - example attached.? Ditto to add an offset calibration mode to compensate for different test lead capacitances.
I have tried a number of capacitance meter circuits over the years and tested several devices of the AADE/LC100 self-oscillating type, which although they use sound principles and theoretically offer good accuracy, in practice suffer from drift when measuring small values of capacitance (and sometimes huge errors when measuring larger capacitors).? This circuit is both sensitive and stable, even on the plugboard I used to try it out.
Peter S ??? ??? G8EZE
|
Re: Cal Lab Magazine - International Journal of Metrology
I have no doubt that you are correct. I'm glad, though, that the farad won out over time. Faraday was remarkable, and deserves having two units named for him.
--Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
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On 9/2/2022 23:39, G8HUL wrote: I don't think it was just the Navy that used Jars as the capacitance unit, it was the 'standard' in the early days, and it was some time before the farad gained popularity, jars can still be found in some sources probably up as far as WW2.
Jeff
-----Original Message-----
From: [email protected] <[email protected]> On Behalf Of Tom Lee
Sent: 02 September 2022 19:23
To: [email protected]
Subject: Re: [Test Equipment Design & Construction] Cal Lab Magazine - International Journal of Metrology
Thank you very much, George. Thanks to you, I now have the 1927 edition of the Admiralty Handbook (archive.org has it, as well as volume 1 of the 1938 edition).
And thanks to this thread, I have learned that the jar, as a unit of capacitance, is 10/9 nF. Apparently, it was mainly used by the Royal Navy. I wonder what the prototype jar was (Leyden? Marmite?)
--Cheers,
Tom
|
Re: Cal Lab Magazine - International Journal of Metrology
I don't think it was just the Navy that used Jars as the capacitance unit, it was the 'standard' in the early days, and it was some time before the farad gained popularity, jars can still be found in some sources probably up as far as WW2.
Jeff
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-----Original Message----- From: [email protected] < [email protected]> On Behalf Of Tom Lee Sent: 02 September 2022 19:23 To: [email protected]Subject: Re: [Test Equipment Design & Construction] Cal Lab Magazine - International Journal of Metrology Thank you very much, George. Thanks to you, I now have the 1927 edition of the Admiralty Handbook (archive.org has it, as well as volume 1 of the 1938 edition). And thanks to this thread, I have learned that the jar, as a unit of capacitance, is 10/9 nF. Apparently, it was mainly used by the Royal Navy. I wonder what the prototype jar was (Leyden? Marmite?) --Cheers, Tom -- Prof. Thomas H. Lee Allen Ctr., Rm. 205 350 Jane Stanford Way Stanford University Stanford, CA 94305-4070 On 9/2/2022 05:20, Labguy wrote: I happen to have a 1931 copy of The Admiralty Handbook of Wireless Telegraphy, a great tome for its day. It speaks of capacitance in jars. I also have a 1927 copy of "Les Ondes Electriques Courtes" (Short Electric Waves). I picked this up at a university book fair for $0.50 some years ago. Makes for great reading to see how things were done in those days. I had a look to see if it contained anything about units for capacitance. It shows circuits for transmitters, but all have the transmit signal that is used to drive output triodes derived from mechanical generators. The output stage shows a capacitor in the tank circuit, but unfortunately no units. Cheers, George VK2KGG -----Original Message----- From: [email protected] <mailto: [email protected]> [mailto: [email protected]] On Behalf Of Tom Lee Sent: Thursday, 1 September 2022 7:16 PM To: [email protected] <mailto: [email protected]> Subject: Re: [Test Equipment Design & Construction] Cal Lab Magazine - International Journal of Metrology I just took a look at a few hobbyist magazines and some product schematics from several different decades, and your speculation looks pretty solid. Based on that random, statistically insignifcant sample, the UK has been quite consistent over time and across publications aimed at quite different readers. The US, not so much, even within a single company. The earliest schematic for HP's first product, the 200A, surprised me with its use of the mu symbol. A schematic for the same product, but of later manufacture, uses "m" for micro. a seemingly backwards step. Textbooks and refereed journals paid the extra ha'penny for a mu, but hobby magazines were a different story. I did not check any German or French pubs to see what conventions were followed there. -- Cheers, Tom
|
Hi Gary, ? One tool that I found useful in tracking down spurii in an unstable UHF amplifier was the shielded pickup loop. I found out about this at an HP, RF, test equipment seminar in Canberra in the mid 1980s. It uses a length of semi rigid miniature coax. The end is formed into a loop, but with a break in the outer. At the end, both the inner and outer are soldered to the outer at the beginning of the loop. I have thought that one day, I will try terminating the end in 50Ω, to see if that flattens the frequency response. ? Regards Rodger Bean ?
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From: [email protected] <[email protected]> On Behalf Of Gary Johnson via groups.io
Sent: Saturday, 3 September 2022 10:09
To: [email protected]
Subject: Re: [Test Equipment Design & Construction] LISN? My one complaint about all commercial LISN units, and the measurement standards, is that their definition of common mode is flawed. K9YC has discussed this extensively. What they do is observe the difference between the two sides of the AC line, but always with respect to the grounding conductor. This makes the bizarre assumption that the grounding conductor does not radiate, which is false. For that reason, my LISN design additionally includes a proper CM current transformer that encompasses all three conductors. This is much more relevant to conducted emissions observations from any device as they actually occur. In fact, if you do anything at all, just measure the common-mode current under whatever test conditions you may establish. This was my primary method of noise finding as an EMC engineer. My favorite tools were Textronix current probes and a spectrum analyzer. They never failed to lead me to the root cause of a noise problem. In the ham radio world, my main tools are a small directional loop antenna and a portable shortwave receiver. That combination will lead me quickly to most noise sources, near or far. Full details on my RFI page at NA6O.com.
Gary NA6O?
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Re: Cal Lab Magazine - International Journal of Metrology
Hi Guys, Some more on conventions in values. Leafing through some of my library of old technical books, I have found the following regarding capacitor designations: Practical Radio Communication, McGraw Hill, 1943, page 78, sec 2.10: “The unit of electrostatic capacity is called the farad.? A condenser which has a capacity of 1 farad would require 1 coulomb of electricity to bring its plates up to a potential difference of 1 volt.” And further on in that paragraph: “In electrical- and radio-engineering practice the values of capacity are generally always expressed in micro-farads or microfarads. The micro-farad is 1/1,000,000 part of a farad, consequently a condenser having a capacity of 1 mf…..” So, the authors, Arthur R. Nilson and J. L. Hornung’s preference is for lower case. In the various circuits in this book, lower values of capacitance are indicated by the use of mmf for picofarad. Electrical and Radio Notes for Wireless Operators, Air Publication 1762, October 1939: designates capacitors only in μf on the circuit diagrams. And mentions smaller value, but only in the text, as micro-microfarads. Reference Data for Radio Engineers, an STC publication, (no publication date), but mentions STC’s supplying of 100 kW – 130 kW transmitters for the BBC’s Empire service. (The case of kW is as printed). Uses “microfarads” and “μ μF”. CREED & CO., LTD’s instruction booklet No 20. The Morse Reperforator model No 7W/3. Uses “Capacitor ‘C’, 5uF” in the components list for fig 2, p6. But “CONDENSOR ‘C’ ?, 1 or 2MF” in fig 3. The Ferguson service manual for their (405 line) TV, model’s 992 – 998, uses uF and pF. Electricity and its uses, J. Munro. Published by The Religious Tract Society, 1890. Mentions condensers, but has no mention of values thereof. The Radio Data Charts; second edition, third reprint by R. T. Beatty, pub by Iliffe & Sons. Talks of micro-microfarads and μμF. The RSGB’s Radio Data Reference Book (1962) uses μF & pF. ? It brings to mind a Ralph Waldo Emerson quote. The first line being “A foolish consistency is the hobgoblin of little minds, adored by little statesmen and philosophers and divines”.? ? Regards Rodger Bean ?
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From: [email protected] <[email protected]> On Behalf Of Tom Lee
Sent: Saturday, 3 September 2022 04:23
To: [email protected]
Subject: Re: [Test Equipment Design & Construction] Cal Lab Magazine - International Journal of Metrology? Thank you very much, George. Thanks to you, I now have the 1927 edition of the Admiralty Handbook (archive.org has it, as well as volume 1 of the 1938 edition).
And thanks to this thread, I have learned that the jar, as a unit of capacitance, is 10/9 nF. Apparently, it was mainly used by the Royal Navy. I wonder what the prototype jar was (Leyden? Marmite?)
--Cheers,
Tom
-- Prof. Thomas H. Lee Allen Ctr., Rm. 205 350 Jane Stanford Way Stanford University Stanford, CA 94305-4070 On 9/2/2022 05:20, Labguy wrote: I happen to have a 1931 copy of The Admiralty Handbook of Wireless Telegraphy, a great tome for its day. It speaks of capacitance in jars. ? I also have a 1927 copy of "Les Ondes Electriques Courtes" (Short Electric Waves). I picked this up at a university book fair for $0.50 some years ago. Makes for great reading to see how things were done in those days. ? I had a look to see if it contained anything about units for capacitance. It shows circuits for transmitters, but all have the transmit signal that is used to drive output triodes derived from mechanical generators. The output stage shows a capacitor in the tank circuit, but unfortunately no units. ? Cheers, George VK2KGG ? ? ? -----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Tom Lee
Sent: Thursday, 1 September 2022 7:16 PM
To: [email protected]
Subject: Re: [Test Equipment Design & Construction] Cal Lab Magazine - International Journal of Metrology ? I just took a look at a few hobbyist magazines and some product schematics from several different decades, and your speculation looks pretty solid. Based on that random, statistically insignifcant sample, the UK has been quite consistent over time and across publications aimed at quite different readers. The US, not so much, even within a single company. The earliest schematic for HP's first product, the 200A, surprised me with its use of the mu symbol. A schematic for the same product, but of later manufacture, uses "m" for micro. a seemingly backwards step. Textbooks and refereed journals paid the extra ha'penny for a mu, but hobby magazines were a different story. ? I did not check any German or French pubs to see what conventions were followed there. ? -- Cheers, Tom ?
?
|
Tesla's notes were the first time that I encountered the
centimeter/centimetre as a unit of both capacitance and inductance.
I see now the connection with the jar -- one jar is 1000 cm of
capacitance, so that a 1 cm capacitance is a millijar.
-- Cheers,
Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
On 9/2/2022 18:45, Brooke Clarke via
groups.io wrote:
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Show quoted text
Hi:
In his Colorado Springs Notebook, Tesla talks about capacitors,
inductors and RF signals, all with the units of meters.
The capacitors were French Champagne bottles filled with salt
water sitting in a salt water bath.? He used the same bottles as
antenna mast insulators, both at the bottom between metal plates
and at the sides of the mast.
--
Have Fun,
Brooke Clarke
axioms:
1. The extent to which you can fix or improve something will be limited by how well you understand how it works.
2. Everybody, with no exceptions, holds false beliefs.
-------- Original Message --------
.
"A?jar?was an early unit of??once used by the British?.?The term originated as the
capacitance of a?. Its value is such that
one??is?9×108?jars and one
jar is 1111?picofarads.
History[]
With early?, changing
the transmission??was most easily
accomplished by changing the number of Leyden jars connected
to the?. While it was
possible to calculate the required capacitance directly, it
was more usual to simply have a book of??which gave the
number of jars needed for any likely?."
Have you ever had?Vegemite?
An Australian sent me a jar as a gag gift.
It's an acquired taste.?
|
Hi:
In his Colorado Springs Notebook, Tesla talks about capacitors,
inductors and RF signals, all with the units of meters.
The capacitors were French Champagne bottles filled with salt water
sitting in a salt water bath.? He used the same bottles as antenna
mast insulators, both at the bottom between metal plates and at the
sides of the mast.
--
Have Fun,
Brooke Clarke
axioms:
1. The extent to which you can fix or improve something will be limited by how well you understand how it works.
2. Everybody, with no exceptions, holds false beliefs.
-------- Original Message --------
toggle quoted message
Show quoted text
.
"A?jar?was an early
unit of??once used by the British?.?The term originated as the
capacitance of a?. Its value is such that one??is?9×108?jars and one jar is
1111?picofarads.
History[]
With early?, changing
the transmission??was most easily
accomplished by changing the number of Leyden jars connected to
the?. While it was possible
to calculate the required capacitance directly, it was more
usual to simply have a book of??which gave the number
of jars needed for any likely?."
Have you ever had?Vegemite? An
Australian sent me a jar as a gag gift.
It's an acquired taste.?
|
My one complaint about all commercial LISN units, and the measurement standards, is that their definition of common mode is flawed. K9YC has discussed this extensively. What they do is observe the difference between the two sides of the AC line, but always with respect to the grounding conductor. This makes the bizarre assumption that the grounding conductor does not radiate, which is false. For that reason, my LISN design additionally includes a proper CM current transformer that encompasses all three conductors. This is much more relevant to conducted emissions observations from any device as they actually occur. In fact, if you do anything at all, just measure the common-mode current under whatever test conditions you may establish. This was my primary method of noise finding as an EMC engineer. My favorite tools were Textronix current probes and a spectrum analyzer. They never failed to lead me to the root cause of a noise problem. In the ham radio world, my main tools are a small directional loop antenna and a portable shortwave receiver. That combination will lead me quickly to most noise sources, near or far. Full details on my RFI page at NA6O.com.
Gary NA6O?
|
Re: Cal Lab Magazine - International Journal of Metrology
:)
I wonder where the Royal Navy kept their standard jars…
Tom Sent from my iThing; please forgive the typos and brevity
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On Sep 2, 2022, at 14:03, Dr. David Kirkby, Kirkby Microwave Ltd <drkirkby@...> wrote:
? On Fri, 2 Sep 2022 at 19:22, Tom Lee < tomlee@...> wrote:
And thanks to this thread, I have learned that the jar, as a unit of
capacitance, is 10/9 nF. Apparently, it was mainly used by the Royal
Navy. I wonder what the prototype jar was (Leyden? Marmite?)
--Cheers,
Tom
Which reminds me, I need to take 1111 pF of coffee to my amateur radio club.
Dave -- Dr. David Kirkby, Kirkby Microwave Ltd, drkirkby@...Telephone 01621-680100./ +44 1621 680100 Registered in England & Wales, company number 08914892. Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom
|
Re: Cal Lab Magazine - International Journal of Metrology
On Fri, 2 Sep 2022 at 19:22, Tom Lee < tomlee@...> wrote:
And thanks to this thread, I have learned that the jar, as a unit of
capacitance, is 10/9 nF. Apparently, it was mainly used by the Royal
Navy. I wonder what the prototype jar was (Leyden? Marmite?)
--Cheers,
Tom
Which reminds me, I need to take 1111 pF of coffee to my amateur radio club.
Dave -- Dr. David Kirkby, Kirkby Microwave Ltd, drkirkby@...Telephone 01621-680100./ +44 1621 680100 Registered in England & Wales, company number 08914892. Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom
|
Re: Cal Lab Magazine - International Journal of Metrology
I suspect that the Australian navy used Vegemite.
Harvey
On 9/2/2022 2:22 PM, Tom Lee wrote:
toggle quoted message
Show quoted text
Thank you very much, George. Thanks to you, I now have the 1927
edition of the Admiralty Handbook (archive.org has it, as well as
volume 1 of the 1938 edition).
And thanks to this thread, I have learned that the jar, as a unit
of capacitance, is 10/9 nF. Apparently, it was mainly used by the
Royal Navy. I wonder what the prototype jar was (Leyden? Marmite?)
--Cheers,
Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
On 9/2/2022 05:20, Labguy wrote:
I happen to have a 1931 copy of The
Admiralty Handbook of Wireless Telegraphy, a great tome for
its day. It speaks of capacitance in jars.
?
I also have a 1927 copy of "Les Ondes
Electriques Courtes" (Short Electric Waves). I picked this
up at a university book fair for $0.50 some years ago. Makes
for great reading to see how things were done in those days.
?
I had a look to see if it contained
anything about units for capacitance. It shows circuits for
transmitters, but all have the transmit signal that is used
to drive output triodes derived from mechanical generators.
The output stage shows a capacitor in the tank circuit, but
unfortunately no units.
?
Cheers,
George
VK2KGG
?
?
?
-----Original
Message-----
From: [email protected]
[mailto:[email protected]]
On Behalf Of Tom Lee
Sent: Thursday, 1 September 2022 7:16 PM
To: [email protected]
Subject: Re: [Test Equipment Design & Construction]
Cal Lab Magazine - International Journal of Metrology
?
I just took a look at a few hobbyist
magazines and some product
schematics from several different
decades, and your speculation looks
pretty solid. Based on that random,
statistically insignifcant sample,
the UK has been quite consistent over
time and across publications aimed
at quite different readers. The US,
not so much, even within a single
company. The earliest schematic for
HP's first product, the 200A,
surprised me with its use of the mu
symbol. A schematic for the same
product, but of later manufacture,
uses "m" for micro. a seemingly
backwards step. Textbooks and refereed
journals paid the extra ha'penny
for a mu, but hobby magazines were a
different story.
?
I did not check any German or French
pubs to see what conventions were
followed there.
?
-- Cheers,
Tom
?
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On Fri, 2 Sept 2022 at 03:08, Tom, wb6b < wb6b@...> wrote: Following this thread with interest.
Interesting about the indirect temperature measurement ideas. Here is a link from a quick search. I'm sure there are other, maybe better, choices with a little more searching. There are far infrared sensors with digital interfaces (I2C), too.
The wavelengths used for non-contact temperature measurement seem to be around the?8 ?m to 14 ?m range.
Tom, wb6b
Farnell had some of those therompiles. I bought one of these
It cost about 5x what the IR LED did, but is much cheaper than the bolometer which Neil, G4DBN mentioned. But I may well buy one of them. But I can mess around with the IR LED and thermopile for little outlay.
Dave
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Ray, W4BYG
John Kolb
Dr. David Kirkby, Kirkby Microwave Ltd
