Re: Making a Q-meter / References etc
On Tue, 30 Aug 2022 at 04:29, Tom Lee < tomlee@...> wrote:
Thanks, but I already noted that explicitly in the first paragraph
of my post. My question is not about the symbols, but about
the units when spelled out. David asserted that the BIPM
says that even in that case, one does not add an s. I cannot find
any reference to such a rule in my search of BIPM docs.
--Tom
On checking, I can't find anything either. Perhaps I read it elsewhere - an NPL document for example.
The SI document is searchable, and a search of volts, watts, moles, amperes does not find any such words. However, there are numerous references to newtons. On page 59 I read
"namely the value of 683 lumens per watt"
But then on page 76 it says
"is exactly 683 lumen per watt",? so again, no s, despite the perceived plural. So both "683 lumens" and "683 luman" are found. There does seem to be some inconsistency
I would agree that "220 ohms" reads better in English than "220 ohm". But if you think about it, a 220 Ω
resistor is not 220 resistors each of one ohm all joined up in series. So is it really a plural?? How about when the number is less than one (i.e. 0.44?
Ω) ??
This needs a bit more research, as I'm sure I did not dream up this thing about not adding an s on the end. But I admit it not stated in the document I attached.
Dave
|
Re: Cal Lab Magazine - International Journal of Metrology
Thanks Dave,
Looks good and informative, also seems unbiassed. I’ve subscribed too,
Dave Skone
Sydney Australia
|
Re: Making a Q-meter / References etc
Exactly. I can't imagine writing "The power dissipated is four
watt." That's why I'm asking David to point me to a specific
reference that prohibits pluralizing unit names.
Just for reference, here's a cut-and-paste from the post in
question:
6) According to the BIPM, the body that
defines the SI standards, virtually all SI units and derived units
should be spelled in lower case, and without the s
- so watt, ampere, volt, not Watts, Volts, Amps etc.
(bold Italics mine)
I agree that Watts, e.g., is wrong, but because of the
capitalization, not the plural.
Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
On 8/29/2022 21:06, Richard Knoppow
wrote:
But by unit symbols do they not mean W for Watt or
omega for ohm?? I can understand? 2 W. Amd not 2 Ws but not 2
Watt instead of 2 Watts.? ?I thin there is a misreading there.?
I.e. confusion between unit symbols and unit names.
-------- Original message --------
Date: 8/29/22 8:15 PM (GMT-08:00)
Subject: Re: [Test Equipment Design & Construction]
Making a Q-meter / References etc
The
Style Manual, the Australian Government Publishing Service
document, states quite categorically that SI unit symbols
never take a plural s
(Wiley Australia, 2002:184). This is based on ISO:31:1992.
Cheers,
Brian
?
?
Thanks for that, David. I do have a
question about plurals,
however. IEEE journal editorial practice explicitly disagrees
with your rule
about plurals when the unit is spelled out. The IEEE says to
add an s, so “2
watts” is correct, according to them. That also conforms with
standard English
grammar rules.
Since my style guide is decades old, I
took a look at the
most recent BIPM SI summary. I could not find any reference
to a pluralization
rule anywhere in its 102 pages (other than a prohibition
against adding an s to
unit abbreviations) but I was only skimming. If you could
point me to a
specific page in that or done other document, I’d appreciate
it greatly.
Cheers,
|
Re: Making a Q-meter / References etc
But by unit symbols do they not mean W for Watt or omega for ohm?? I can understand? 2 W. Amd not 2 Ws but not 2 Watt instead of 2 Watts.? ?I thin there is a misreading there.? I.e. confusion between unit symbols and unit names.
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Show quoted text
-------- Original message -------- From: Brian <brianclarke01@...> Date: 8/29/22 8:15 PM (GMT-08:00) Subject: Re: [Test Equipment Design & Construction] Making a Q-meter / References etc
The Style Manual, the Australian Government Publishing Service
document, states quite categorically that SI unit symbols never take a plural s
(Wiley Australia, 2002:184). This is based on ISO:31:1992.
Cheers, Brian
?
?
Thanks for that, David. I do have a question about plurals,
however. IEEE journal editorial practice explicitly disagrees with your rule
about plurals when the unit is spelled out. The IEEE says to add an s, so “2
watts” is correct, according to them. That also conforms with standard English
grammar rules.
Since my style guide is decades old, I took a look at the
most recent BIPM SI summary. I could not find any reference to a pluralization
rule anywhere in its 102 pages (other than a prohibition against adding an s to
unit abbreviations) but I was only skimming. If you could point me to a
specific page in that or done other document, I’d appreciate it greatly.
Cheers,
|
Re: Making a Q-meter / References etc
Hi Dave, Thank you for the feedback, an amended version is attached. ? - The input power of watt is rounded to the nearest integer - it would be useful if it allowed a few decimal places, as entering powers in nW or similar is not unusual. But if I enter 1.4 W, it gets rounded to 1 in the input display, but the outputs are more sensible.
Done. (Working in the TV broadcast industry, most of the transmitters that I worked on were 100W up to 30KW). ? - You might consider whether it's worthwhile adding dbW. I know it's not used a lot, but our amateur licenses in the UK are specified in dBW now, not watt.
Done. - You say dBm is referenced to 1 mW, and dBuV is referenced to 1 uV, but for dBmV, you spell out the millivolt, rather than just put 1 mV.
Done. - You mention dBu, but don't allow anyone to perform any calculations with it.
For dBu, use 600Ω and ignore Watts, dBm, dBmV & dbuV. - There's a spelling error – impemdence.
- Done.
- According to the BIPM, the body that defines the SI standards, virtually all SI units and derived units should be spelled in lower case, and without the s - so watt, ampere, volt, not Watts, Volts, Amps etc. I think the only exception to this is degrees Celsius. (I have attached a copy of the SI document).
Just a personal preference. Re SI, having lived through: fps, cgs, MKS and SI. It’s all just numbers, although at least in emu & esu (electrostatic units & electromagnetic units) there was no π in a constant. And anyway, SI is just a collection of precisely defined, arbitrary units, relating to the an ordinary planet, orbiting around an ordinary star, in remote part of a galaxy that we call The Milky Way. They have as much in common with the rest of the universe as the distance from the thumb to the nose of whoever is the current reigning monarch. (lol). 7) If on the voltage gain section, I put an input of 1 V, and an output of -2 V, the calculator shows an error. Not so easy to fix, I could square V1 & V2 then square root them to remove the negative sign, but I don’t believe that it is necessary.? And any changes that gave a negative dB would imply a loss where none exists. There may be a function that only takes the modulus of a number entry. But I think it would be easier to remember that you are using an inverting amplifier. * It's easy to configure an op-amp to have a negative gain (inverting amplifier). * A VNA will often measure a reflected voltage that is 180 degrees out of phase with respect to the input. ? Rodger Bean ? ?
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From: [email protected] <[email protected]> On Behalf Of Dr. David Kirkby, Kirkby Microwave Ltd
Sent: Tuesday, 30 August 2022 07:35
To: [email protected]
Subject: Re: [Test Equipment Design & Construction] Making a Q-meter / References etc? That's useful. Can I suggest a few improvements? 1) The input power of watt is rounded to the nearest integer - it would be useful if it allowed a few decimal places, as entering powers in nW or similar is not unusual. But if I enter 1.4 W, it gets rounded to 1 in the input display, but the outputs are more sensible. 2) You might consider whether it's worthwhile adding dbW. I know it's not used a lot, but our amateur licenses in the UK are specified in dBW now, not watt. 3) You say dBm is referenced to 1 mW, and dBuV is referenced to 1 uV, but for dBmV, you spell out the millivolt, rather than just put 1 mV. 4) You mention dBu, but don't allow anyone to perform any calculations with it. 5) There's a spelling error - impemdence 6) According to the BIPM, the body that defines the SI standards, virtually all SI units and derived units should be spelled in lower case, and without the s - so watt, ampere, volt, not Watts, Volts, Amps etc. I think the only exception to this is degrees Celsius. (I have attached a copy of the SI document). 7) If on the voltage gain section, I put an input of 1 V, and an output of -2 V, the calculator shows an error. * It's easy to configure an op-amp to have a negative gain (inverting amplifier). * A VNA will often measure a reflected voltage that is 180 degrees out of phase with respect to the input. I personally would take the absolute magnitudes of the voltages and use that to calculate the gain, so as to not show an error when the input and output are of a different sign. 8) According to the BIPM, there should be a space between a number and a unit - ie 2 uV not 2uV. 9) You are inconsistent in your use of P1 and P 1, and likewise V2 and V 2. Personally I would remove the spaces, as spaces imply multiplication. Or perhaps consider the use of subscripts. 10) I think the last part is potentially wrong, if the DUT does not accept all the input power. If the device reflects a lot of power on the left hand side, then the input power can be high, the output power low, but the dissipation is also low. When calculating antenna gains, the values are in terms of power accepted by the antenna, not the input power to the antenna. I can think of two things you could usefully add. 1) The ability to calculate output voltages given an input voltage and a gain. 2) Noise temperature to noise figure and noise factor conversions. It looks like a useful calculator, but there are some random suggestions of mine. Dr David Kirkby Ph.D
Email: drkirkby@... Web:
Kirkby Microwave Ltd (Tel 01621-680100 / +44 1621-680100)
Stokes Hall Lodge, Burnham Rd, Chelmsford, Essex, CM3 6DT.
? ? I created this Excel spreadsheet to convert between Watts, Volts, dBm, dBmV and dBuV. It has simple protection applied to guard against accidental overwriting of a formula. There is no password required to turn it off. To turn the protection off, got to “file” then “info”. ? Rodger Bean ? ? Well the box turned out a little silly, basically a short from BNC to BNC.
?I setup a series LC 230uh, 110pf (variable) I could not get a dip, (still unsure why, not my first rodeo)
So, I installed a better than 1%, 1Ω resistor as the DUT and used 50kHz to avoid any strays.
Using db on my HP 400E (unknown calibration) Using 1 volt input and 1Ω load, I get -26.45db with the db scale and using a voltage ratio 1/ 0.0371 = 26.95 = 28.6db
?I don't know why the printed scale would not be in agreement.
?The correct answer (according to the paper) is 28.3db, so pretty good agreement using the voltage ratio! The meter error difference is 1.3mv.
?My favorite db to voltage, voltage to db calculator.
? I received parts for another project, so this is now on the back burner, but will keep reading in case someone has ideas where I went wrong.
??????????????????????????????????????????? Thanks, Mikek
* After talking with a calibration facility, I sent my HP 400E in for calibration ($25 shipping) Then they told me, "we can't calibrate that"
?After I get my HP 3400 working properly, I'll check, I think that someone will be able to calibrate that.
>I decided to tighten it up and put the termination at the meter.
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?? Mikek ???????
?????????????????????????? ?
|
Re: Making a Q-meter / References etc
Thanks, but I already noted that explicitly in the first paragraph
of my post. My question is not about the symbols, but about
the units when spelled out. David asserted that the BIPM
says that even in that case, one does not add an s. I cannot find
any reference to such a rule in my search of BIPM docs.
--Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
On 8/29/2022 20:15, Brian wrote:
toggle quoted message
Show quoted text
The
Style Manual, the Australian Government Publishing Service
document, states quite categorically that SI unit symbols
never take a plural s
(Wiley Australia, 2002:184). This is based on ISO:31:1992.
Cheers,
Brian
?
?
Thanks for that, David. I do have a
question about plurals,
however. IEEE journal editorial practice explicitly disagrees
with your rule
about plurals when the unit is spelled out. The IEEE says to
add an s, so “2
watts” is correct, according to them. That also conforms with
standard English
grammar rules.
Since my style guide is decades old, I
took a look at the
most recent BIPM SI summary. I could not find any reference
to a pluralization
rule anywhere in its 102 pages (other than a prohibition
against adding an s to
unit abbreviations) but I was only skimming. If you could
point me to a
specific page in that or done other document, I’d appreciate
it greatly.
Cheers,
|
Re: Making a Q-meter / References etc
The Style Manual, the Australian Government Publishing Service
document, states quite categorically that SI unit symbols never take a plural s
(Wiley Australia, 2002:184). This is based on ISO:31:1992.
Cheers, Brian
?
?
Thanks for that, David. I do have a question about plurals,
however. IEEE journal editorial practice explicitly disagrees with your rule
about plurals when the unit is spelled out. The IEEE says to add an s, so “2
watts” is correct, according to them. That also conforms with standard English
grammar rules.
Since my style guide is decades old, I took a look at the
most recent BIPM SI summary. I could not find any reference to a pluralization
rule anywhere in its 102 pages (other than a prohibition against adding an s to
unit abbreviations) but I was only skimming. If you could point me to a
specific page in that or done other document, I’d appreciate it greatly.
Cheers,
|
Re: Making a Q-meter / References etc
Nice calculator, thanks. Will be much better than looking for an on-line one when needed.
If anyone is interested using small series capacitors to measure Q using the 3 db points, I have about 20,000 1.8pF capacitors in the box of reels of surface mount capacitors I picked up at auction. Only problem is they are size 0402 so you would need a magnifier, steady hands, and a small soldering iron tip to use them. I'll mail a handful, free, to anyone that sends me a mailing address to kk6il@.... Don't reply to the list and clutter it up please.
Also have a only a few 0.007 ohm resistors, large 2010 size. Only 1 each to first 10 requests.
John
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On 8/29/2022 7:36 AM, Mikek wrote: Well the box turned out a little silly, basically a short from BNC to BNC.
?I setup a series LC 230uh, 110pf (variable) I could not get a dip, (still unsure why, not my first rodeo)
So, I installed a better than 1%, 1Ω resistor as the DUT and used 50kHz to avoid any strays.
|
Re: Making a Q-meter / References etc
Thanks for that, David. I do have a question about plurals, however. IEEE journal editorial practice explicitly disagrees with your rule about plurals when the unit is spelled out. The IEEE says to add an s, so “2 watts” is correct, according to them. That also conforms with standard English grammar rules.
Since my style guide is decades old, I took a look at the most recent BIPM SI summary. I could not find any reference to a pluralization rule anywhere in its 102 pages (other than a prohibition against adding an s to unit abbreviations) but I was only skimming. If you could point me to a specific page in that or done other document, I’d appreciate it greatly.
Cheers, Tom Sent from my iThing; please forgive the typos and brevity
toggle quoted message
Show quoted text
On Aug 29, 2022, at 14:36, Dr. David Kirkby, Kirkby Microwave Ltd <drkirkby@...> wrote:
? That's useful. Can I suggest a few improvements?
1) The input power of watt is rounded to the nearest integer - it would be useful if it allowed a few decimal places, as entering powers in nW or similar is not unusual. But if I enter 1.4 W, it gets rounded to 1 in the input display, but the outputs are more sensible.
2) You might consider whether it's worthwhile adding dbW. I know it's not used a lot, but our amateur licenses in the UK are specified in dBW now, not watt.
3) You say dBm is referenced to 1 mW, and dBuV is referenced to 1 uV, but for dBmV, you spell out the millivolt, rather than just put 1 mV.
4) You mention dBu, but don't allow anyone to perform any calculations with it.
5) There's a spelling error - impemdence 6) According to the BIPM, the body that defines the SI standards, virtually all SI units and derived units should be spelled in lower case, and without the s - so watt, ampere, volt, not Watts, Volts, Amps etc. I think the only exception to this is degrees Celsius. (I have attached a copy of the SI document).
7) If on the voltage gain section, I put an input of 1 V, and an output of -2 V, the calculator shows an error.
* It's easy to configure an op-amp to have a negative gain (inverting amplifier).
* A VNA will often measure a reflected voltage that is 180 degrees out of phase with respect to the input.
I personally would take the absolute magnitudes of the voltages and use that to calculate the gain, so as to not show an error when the input and output are of a different sign.
8) According to the BIPM, there should be a space between a number and a unit - ie 2 uV not 2uV.
9) You are inconsistent in your use of P1 and P 1, and likewise V2 and V 2. Personally I would remove the spaces, as spaces imply multiplication. Or perhaps consider the use of subscripts.
10) I think the last part is potentially wrong, if the DUT does not accept all the input power. If the device reflects a lot of power on the left hand side, then the input power can be high, the output power low, but the dissipation is also low. When calculating antenna gains, the values are in terms of power accepted by the antenna, not the input power to the antenna.
I can think of two things you could usefully add.
1) The ability to calculate output voltages given an input voltage and a gain.
2) Noise temperature to noise figure and noise factor conversions.
It looks like a useful calculator, but there are some random suggestions of mine.
Dave
Dr David Kirkby Ph.D Email: drkirkby@... Web: Kirkby Microwave Ltd (Tel 01621-680100 / +44 1621-680100)
Stokes Hall Lodge, Burnham Rd, Chelmsford, Essex, CM3 6DT. I created this Excel spreadsheet to convert between Watts, Volts, dBm, dBmV and dBuV. It has simple protection applied to guard against accidental overwriting of a formula. There is no password required to turn it off. To turn the protection off, got to “file” then “info”. ? Rodger Bean ? ? Well the box turned out a little silly, basically a short from BNC to BNC.
?I setup a series LC 230uh, 110pf (variable) I could not get a dip, (still unsure why, not my first rodeo)
So, I installed a better than 1%, 1Ω resistor as the DUT and used 50kHz to avoid any strays.
Using db on my HP 400E (unknown calibration) Using 1 volt input and 1Ω load, I get -26.45db with the db scale and using a voltage ratio 1/ 0.0371 = 26.95 = 28.6db
?I don't know why the printed scale would not be in agreement.
?The correct answer (according to the paper) is 28.3db, so pretty good agreement using the voltage ratio! The meter error difference is 1.3mv.
?My favorite db to voltage, voltage to db calculator.
? I received parts for another project, so this is now on the back burner, but will keep reading in case someone has ideas where I went wrong.
??????????????????????????????????????????? Thanks, Mikek
* After talking with a calibration facility, I sent my HP 400E in for calibration ($25 shipping) Then they told me, "we can't calibrate that"
?After I get my HP 3400 working properly, I'll check, I think that someone will be able to calibrate that.
>I decided to tighten it up and put the termination at the meter.
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?? Mikek ???????
?????????????????????????? ?
|
Re: Making a Q-meter / References etc
That's useful. Can I suggest a few improvements?
1) The input power of watt is rounded to the nearest integer - it would be useful if it allowed a few decimal places, as entering powers in nW or similar is not unusual. But if I enter 1.4 W, it gets rounded to 1 in the input display, but the outputs are more sensible.
2) You might consider whether it's worthwhile adding dbW. I know it's not used a lot, but our amateur licenses in the UK are specified in dBW now, not watt.
3) You say dBm is referenced to 1 mW, and dBuV is referenced to 1 uV, but for dBmV, you spell out the millivolt, rather than just put 1 mV.
4) You mention dBu, but don't allow anyone to perform any calculations with it.
5) There's a spelling error - impemdence 6) According to the BIPM, the body that defines the SI standards, virtually all SI units and derived units should be spelled in lower case, and without the s - so watt, ampere, volt, not Watts, Volts, Amps etc. I think the only exception to this is degrees Celsius. (I have attached a copy of the SI document).
7) If on the voltage gain section, I put an input of 1 V, and an output of -2 V, the calculator shows an error.
* It's easy to configure an op-amp to have a negative gain (inverting amplifier).
* A VNA will often measure a reflected voltage that is 180 degrees out of phase with respect to the input.
I personally would take the absolute magnitudes of the voltages and use that to calculate the gain, so as to not show an error when the input and output are of a different sign.
8) According to the BIPM, there should be a space between a number and a unit - ie 2 uV not 2uV.
9) You are inconsistent in your use of P1 and P 1, and likewise V2 and V 2. Personally I would remove the spaces, as spaces imply multiplication. Or perhaps consider the use of subscripts.
10) I think the last part is potentially wrong, if the DUT does not accept all the input power. If the device reflects a lot of power on the left hand side, then the input power can be high, the output power low, but the dissipation is also low. When calculating antenna gains, the values are in terms of power accepted by the antenna, not the input power to the antenna.
I can think of two things you could usefully add.
1) The ability to calculate output voltages given an input voltage and a gain.
2) Noise temperature to noise figure and noise factor conversions.
It looks like a useful calculator, but there are some random suggestions of mine.
Dave
Dr David Kirkby Ph.D Email: drkirkby@... Web: Kirkby Microwave Ltd (Tel 01621-680100 / +44 1621-680100)
Stokes Hall Lodge, Burnham Rd, Chelmsford, Essex, CM3 6DT.
I created this Excel spreadsheet to convert between Watts, Volts, dBm, dBmV and dBuV. It has simple protection applied to guard against accidental overwriting of a formula. There is no password required to turn it off. To turn the protection off, got to “file” then “info”. ? Rodger Bean ? ? Well the box turned out a little silly, basically a short from BNC to BNC.
?I setup a series LC 230uh, 110pf (variable) I could not get a dip, (still unsure why, not my first rodeo)
So, I installed a better than 1%, 1Ω resistor as the DUT and used 50kHz to avoid any strays.
Using db on my HP 400E (unknown calibration) Using 1 volt input and 1Ω load, I get -26.45db with the db scale and using a voltage ratio 1/ 0.0371 = 26.95 = 28.6db
?I don't know why the printed scale would not be in agreement.
?The correct answer (according to the paper) is 28.3db, so pretty good agreement using the voltage ratio! The meter error difference is 1.3mv.
?My favorite db to voltage, voltage to db calculator.
? I received parts for another project, so this is now on the back burner, but will keep reading in case someone has ideas where I went wrong.
??????????????????????????????????????????? Thanks, Mikek
* After talking with a calibration facility, I sent my HP 400E in for calibration ($25 shipping) Then they told me, "we can't calibrate that"
?After I get my HP 3400 working properly, I'll check, I think that someone will be able to calibrate that.
>I decided to tighten it up and put the termination at the meter.
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?? Mikek ???????
?????????????????????????? ?
|
Re: Making a Q-meter / References etc
I created this Excel spreadsheet to convert between Watts, Volts, dBm, dBmV and dBuV. It has simple protection applied to guard against accidental overwriting of a formula. There is no password required to turn it off. To turn the protection off, got to “file” then “info”. ? Rodger Bean ?
toggle quoted message
Show quoted text
From: [email protected] <[email protected]> On Behalf Of Mikek
Sent: Tuesday, 30 August 2022 00:36
To: [email protected]
Subject: Re: [Test Equipment Design & Construction] Making a Q-meter / References etc? Well the box turned out a little silly, basically a short from BNC to BNC.
?I setup a series LC 230uh, 110pf (variable) I could not get a dip, (still unsure why, not my first rodeo)
So, I installed a better than 1%, 1Ω resistor as the DUT and used 50kHz to avoid any strays.
Using db on my HP 400E (unknown calibration) Using 1 volt input and 1Ω load, I get -26.45db with the db scale and using a voltage ratio 1/ 0.0371 = 26.95 = 28.6db
?I don't know why the printed scale would not be in agreement.
?The correct answer (according to the paper) is 28.3db, so pretty good agreement using the voltage ratio! The meter error difference is 1.3mv.
?My favorite db to voltage, voltage to db calculator.
? I received parts for another project, so this is now on the back burner, but will keep reading in case someone has ideas where I went wrong.
??????????????????????????????????????????? Thanks, Mikek
* After talking with a calibration facility, I sent my HP 400E in for calibration ($25 shipping) Then they told me, "we can't calibrate that"
?After I get my HP 3400 working properly, I'll check, I think that someone will be able to calibrate that.
>I decided to tighten it up and put the termination at the meter.
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?? Mikek ???????
?????????????????????????? ?
|
Cal Lab Magazine - International Journal of Metrology
I don't know about others, but I was completely unaware of this.
I was made aware of it by someone at METAS, who has published there. So if METAS publishes there, it is worth knowing about. It is obviously not one of these useless scam journals, which exist to do little more than boost the publication record of dubious academics.
Dr David Kirkby Ph.D Email: drkirkby@... Web: Kirkby Microwave Ltd (Tel 01621-680100 / +44 1621-680100)
Stokes Hall Lodge, Burnham Rd, Chelmsford, Essex, CM3 6DT.
|
Re: Making a Q-meter / References etc
Well the box turned out a little silly, basically a short from BNC to BNC.
?I setup a series LC 230uh, 110pf (variable) I could not get a dip, (still unsure why, not my first rodeo)
So, I installed a better than 1%, 1Ω resistor as the DUT and used 50kHz to avoid any strays.
Using db on my HP 400E (unknown calibration) Using 1 volt input and 1Ω load, I get -26.45db with the db scale and using a voltage ratio 1/ 0.0371 = 26.95 = 28.6db
?I don't know why the printed scale would not be in agreement.
?The correct answer (according to the paper) is 28.3db, so pretty good agreement using the voltage ratio! The meter error difference is 1.3mv.
?My favorite db to voltage, voltage to db calculator.
? I received parts for another project, so this is now on the back burner, but will keep reading in case someone has ideas where I went wrong.
??????????????????????????????????????????? Thanks, Mikek
* After talking with a calibration facility, I sent my HP 400E in for calibration ($25 shipping) Then they told me, "we can't calibrate that"
?After I get my HP 3400 working properly, I'll check, I think that someone will be able to calibrate that.
>I decided to tighten it up and put the termination at the meter.
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?? Mikek ???????
??????????????????????????
?
|
Re: Making a Q-meter / References etc
Measurements using a single voltage measurement with an air coil may not
be easily reproducible. Air coil selected at the time for computing Q
using an online coil calculator.
is updated with easier to replicate Toroidal inductor, shown in section
"Single Voltage T50-2 37T #24 with 330pF C0G Q Measurement"
Signal generator is set to near maximum output to increase DUT Vout
measurement. Using Oscilloscope Averaging and RMS measure for greater
accuracy.
John KN5L
|
Re: Making a Q-meter / References etc
Thanks Steve,
As I read EMRFD, the external 50 Ohm resistor is intended to be input Z
of a Voltmeter or Spectrum Analyzer.
The solutions I just posted is using a high Z oscilloscope as a voltmeter.
It takes one line of code to factor in external 50 ohm, Rs = 1/(1/Rs - 1/50)
When using a volt meter, my preference to compute Rs directly without dB
computation.
John KN5L
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On 8/28/22 7:23 PM, Steve Ratzlaff wrote: The ARRL publication Experimental Methods in RF Design (aka EMRFD),
first published around 2003, has the same? info on using notch depth to
compute Q for a series or parallel circuit, p. 7.36, Chapter 7.9, "Q
Measurement of LC Resonators". Both series and parallel trap methods are
shown along with the formulas.
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Re: Making a Q-meter / References etc
The ARRL publication Experimental Methods in RF Design (aka
EMRFD), first published around 2003, has the same? info on using
notch depth to compute Q for a series or parallel circuit, p.
7.36, Chapter 7.9, "Q Measurement of LC Resonators". Both series
and parallel trap methods are shown along with the formulas.
73,
Steve AA7U
On 8/28/2022 5:26 AM, Mikek wrote:
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I found this in my files while looking for something else.
Method Simplifies Testing High-Q devices, Alan Victor.
I can't get the Figure 1, Table 1, and figure 2 to load.
If anyone is interested I have a paper copy and can upload it to
Dropbox.
It's just a series LC circuit driven by 50Ω and loaded with 50Ω.
Voltage is read with a voltmeter, and some voltage divider math
gets
you notch depth in db that converts to R of the inductor.
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Re: Making a Q-meter / References etc
I knew an Alan Victor when I was in grad school at U of F.? I wonder if he is the same one. ? 73 (Regards). ? Max K 4 O D S. ? I've Never Lost the Wonder. ?
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From: [email protected] [mailto:[email protected]] On Behalf Of Mikek
Sent: Sunday, August 28, 2022 7:26 AM
To: [email protected]
Subject: Re: [Test Equipment Design & Construction] Making a Q-meter / References etc ? I found this in my files while looking for something else.
Method Simplifies Testing High-Q devices, Alan Victor.
I can't get the Figure 1, Table 1, and figure 2 to load.
If anyone is interested I have a paper copy and can upload it to
Dropbox.
It's just a series LC circuit driven by 50Ω and loaded with 50Ω.
Voltage is read with a voltmeter, and some voltage divider math gets
you notch depth in db that converts to R of the inductor.
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Re: Making a Q-meter / References etc
The external 50 ohm load resistor is not required, and increases
solution complexity.
Section "Voltage Ratio Q Measurement" is updated with new SimSmith
window image "Single Voltage, 81mV, Q Measurement." Using single
measurement, across the DUT and computing Q using DUT inductance.
John KN5L
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On 8/28/22 4:37 PM, John KN5L wrote: Got it, Attached is SimSmith solution with measured V to Q equation.
Equations are:
XL=2*Pi*G.MHz*L1.H*1e6;
Rs=(R1.V.M*50)/(2-R1.V.M);
Rs=1/(1/Rs-1/50);
Q=XL/Rs;
John KN5L
On 8/28/22 3:37 PM, John KN5L wrote:
Added a 50 Ohm load to BNC connector fixture shown in:
Section: "Voltage Ratio Q Measurement" With Generator set to 1Vrms
output, Oscilloscope measures = 49.5mV
Using SimSmith model to reverse out Q results with Q = 110.
Need a mV and L to Q formula such that Q can be computed within SimSmith.
John KN5L
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Re: Making a Q-meter / References etc
I uploaded the original article to the files section.? Notification should show shortly.
Ron
Thank you. I will delete the poorer version I created from the photographs.
RF Volt meters are much less common than power meters or VNAs. Given both ends are terminated in 50 ohm, this seems more easily done with a VNA, and using the VNA to provide the 50 ohm termination. Unless I am missing something.
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: Making a Q-meter / References etc
Ron,
many thanks for the clean copy of the article.
73, Stay Safe,
Robin, G8DQX
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On 28/08/2022 20:36, Ron wrote: I uploaded the original article to the files section.? Notification should show shortly.
Ron
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Dr. David Kirkby, Kirkby Microwave Ltd
Brian
John Kolb