Re: Making a Q-meter / References etc

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Could larger resistor values be used for measuring larger values of Rs.? I think the answer is yes.? If the signal source is an RF signal generator the load on it would need to always be 50 ohms.?

?

73 (Regards).

?

Max K 4 O D S.

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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 11:57 AM
To: [email protected]
Subject: Re: [Test Equipment Design & Construction] Making a Q-meter / References etc

?

Sorry forgot my proposed Layout.

Re: Making a Q-meter / References etc

#308

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

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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

ss-Q-Rs.png

Re: Making a Q-meter / References etc

#307

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

Q-DUT.jpg

Re: Making a Q-meter / References etc

#306

I decided to tighten it up and put the termination at the meter.
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?? Mikek ???????
??????????????????????????

Q Tester tightened up.jpg

File /Q-factor (Q is the inverse of dissipation factor DF)./Method simplifies testing high-Q devices; Alan Victor, EDN Feb 2002.pdf uploaded #file-notice

Group Notification

#303

The following files and folders have been uploaded to the Files area of the [email protected] group.

/Q-factor (Q is the inverse of dissipation factor DF)./Method simplifies testing high-Q devices; Alan Victor, EDN Feb 2002.pdf

By: Ron <roncarlson.email@...>

Description:
Alan Victor's article in EDN 2002 on High-Q device testing

Re: Making a Q-meter / References etc

#302

I uploaded the original article to the files section.? Notification should show shortly.

Ron

Re: Making a Q-meter / References etc

#301

Use the five-sided box to mount everything, not the lid.

Pete

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On Sun, Aug 28, 2022 at 5:52 PM Mikek <amdx@...> wrote:

I want to try this, since I now have an HP 3400 RF voltmeter. It will only go to 10 MHz. I'll use my scope after that.
?I'll be using a 4" x 2" x 1" tall cast box.See attached pictures. I'll install Teflon* stand offs to solder DUT to. *(if I find them)
I'll put BNC connectors on the box.
Some questions about best RF practices.
1) Do I want the 50Ω termination internal to my box or at the end of the cable going to the meter. (high input impedance meter)
2)? Can ground to the box or should I put in copper straps.
3) Tell me what I should do different.

?????????????????????? Mikek

?

Re: Making a Q-meter / References etc

#300

On Sun, Aug 28, 2022 at 06:07 AM, Mikek wrote:

My scanner is finicky these days, I took pictures.
If they don't help, I'll work with my scanner.
?????????????????????? Mikek

I converted your photos into a PDF using the free open-source GIMP.

I put it here in the files section of the group
/g/Test-Equipment-Design-Construction/files/Q-factor%20%28Q%20is%20the%20inverse%20of%20dissipation%20factor%20DF%29./Method%20Simplifies%20high-Q%20devices%20EDN%20Magazine%201st%20Feb%202002%20by%20Alan%20Victor.pdf

Re: Making a Q-meter / References etc

#299

SimSmith model attached,

John KN5L

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On 8/28/22 12:22 PM, Mikek wrote:
I'm missing a detail. It looks like we need to set the 1 Volt input
without the DUT connected, then insert the DUT and tune for lowest voltage.
(no need for constant voltage source as I said before)

ss-V-Q.png

Re: Making a Q-meter / References etc

#298

Thanks, no edit though :-(
???????????????? Mikek

Re: Making a Q-meter / References etc

#296

I'm missing a detail. It looks like we need to set the 1 Volt input without the DUT connected, then insert the DUT and tune for lowest voltage.
(no need for constant voltage source as I said before)
?Is there an edit function with this software? Or delete?

?Help, with best RF practice.
??????????????????? Mikek

?Going to clean my bench so I can get started.

Re: Making a Q-meter / References etc

#295

Sorry forgot my proposed Layout.

Q Tester.jpg

Re: Making a Q-meter / References etc

#294

I want to try this, since I now have an HP 3400 RF voltmeter. It will only go to 10 MHz. I'll use my scope after that.
?I'll be using a 4" x 2" x 1" tall cast box.See attached pictures. I'll install Teflon* stand offs to solder DUT to. *(if I find them)
I'll put BNC connectors on the box.
Some questions about best RF practices.
1) Do I want the 50Ω termination internal to my box or at the end of the cable going to the meter. (high input impedance meter)
2)? Can ground to the box or should I put in copper straps.
3) Tell me what I should do different.

?????????????????????? Mikek

?

Project box.jpg

Re: Making a Q-meter / References etc

#292

Appended to: 
is section "FT114-31 9T SRF Q Measurement" which demonstrates measuring
a high inductance Ferrite inductor at Self Resonant Frequency (SRF).

This measurement demonstrates the difficulty measuring Ferrite inductors
using S11 Real and Imaginary measurements. Inductive reactance, ImagZ,
is invalid above about 4MHz. Above 4MHz, ImagZ is sum of inductive and
capacitive reactance.

John KN5L

Re: Making a Q-meter / References etc

#291

Obviously, you would need to generate a more finely incremented Table one.
????????????????????????????? Mikek

Re: Making a Q-meter / References etc

#290

My scanner is finicky these days, I took pictures.
If they don't help, I'll work with my scanner.
?????????????????????? Mikek

Design Ideas Q meter 1.jpg

Design Ideas Q meter 2.jpg

Re: Making a Q-meter / References etc

#289

On Sun, 28 Aug 2022 at 13:26, Mikek <amdx@...> wrote:

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.

I would appreciate a scan if you can do so. I can't get images to load either, so it's essentially impossible to follow the description.

Re: Making a Q-meter / References etc

#288

I found this in my files while looking for something else.
Method Simplifies Testing High-Q devices, Alan Victor.
https://www.edn.com/method-simplifies-testing-high-q-devices/
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.

Re: Optimal full scale deflection on analog meters

Rodger Bean

#287

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The Sangamo Weston S 82 galvanometer pictured has a significant overshoot when given a step increase in current. The coil is 146Ω and it is recommended that a 2KΩ resistor be put in parallel with it, if the galvo is being used with a high source impedance. For those who revel in the mathematics of galvo damping. There is an interesting paper here: ?

?

Rodger Bean

?

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From: [email protected] <[email protected]> On Behalf Of Pete_G4GJL
Sent: Thursday, 25 August 2022 22:30
To: [email protected]
Subject: Re: [Test Equipment Design & Construction] Optimal full scale deflection on analog meters

?

No surprise, as the movement would normally be damped by the very low resistance of the thermocouple to which it should be connected. With the data you have, make a 0-1 Amp ammeter and test that with a 1/2 FSD current. You will find it exhibits 'normal' damping. That is unless you have a thermocouple to try it out on!

?

Pete

G4GJL

?

On Wed, Aug 24, 2022 at 9:34 PM Mikek <amdx@...> wrote:

Here's a video I posted of the Multiply by Q meter from the 260A.

?I just found it interesting that it was so Undamped.
????????????????????????????????? Mikek

P3050009A.jpg

Re: Making a Q-meter / References etc

#286

Would it not be possible to come up with a temperature stable (within reasonable room temp) in a 1" x 1" size or however you make it low inductance and make a Kelvin connection to that.
?Have a switch to set the drive current, that also sets the gain of the Q meter amp that is driven by the Kelvin connection.
I'm assuming a parallel connection, although I do see one advantage of a series connection and that is less interference from local AM stations with big coils.
?Tell me where I'm wrong on this so I can learn.
??????????????????????????????????? Thanks, Mikek
As far as overwhelming response, I can't get enough!