Re: [time-nuts] potential low-RFI power supply

[ed breya]

Taka,

You can set up a mini conducted-EMC lab with a few additional items that 
can be purchased, and some that you can make yourself, if you have the 
right parts.


The most important item is a wideband AC current probe or transformer. A 
commercial clip-on type is most convenient, and ideally it should have 
jaws big enough to clip around fairly large conductors, like an entire 
power cord. I have some nice Tek P6021s, but they are too small for 
large conductors - they only go up to about 3-4 mm diameter wire. I 
don't know what's available out there that would work for bigger stuff, 
but there may be some. It's not that you need a high current capability, 
but that it's very convenient to go around large cable assemblies or 
even components. In the old days, EMC labs would use nice big shielded 
split-toroid HF current transformers to clamp around the big stuff - I 
would imagine it's the same nowadays. When I need such measurements, I 
just wind up a transformer on a ferrite core. What you don't want is one 
of those big clamp-on amp meter type things - they are for measuring 
high currents at line frequency, and can't reach SMPS type frequencies. 
About 20-50 MHz or so BW is plenty, and you don't need to worry about 
the low end response like at line frequency, although that would be nice 
too.


I'm guessing you won't find such a probe with all these characteristics 
commercially, unless you get a high precision, professional type one 
made for EMC or SMPS design use, and likely very spendy. So, it's an 
opportunity to make your own. I'll explain later how to make some, but 
at this point it's necessary to know what you have available, 
ferrite-wise. Many people have nice collections of magnetic cores and 
parts, new or salvaged, so already may have plenty of pieces to play 
with. For SMPS/EMC use, it's good to have some nice ferrite power 
toroids - the bigger (like 2-3" ID) the better - for winding 
transformers with a hole big enough for a one-turn pass-through loop of 
big stuff, like a power cord, or even its plug too. For clamp-ons, you 
can use any un-gapped two-piece core like E-I, C-I, C-C, etc, again, the 
bigger the better, for putting around cords and such. If you have a 
bunch, that's great. Also, if you have some junker equipment with SMPS 
stuff in it, you can likely salvage many pieces that you can use.


Remember, all this current probe/transformer stuff is about measuring 
high speed common-mode currents, not operating loop currents in 
circuits. You'll want to first explore the time domain with a scope, 
then later an SA.


The next category of ferrites is more of the same stuff, but for 
steering the currents away from where they're not wanted, to where they 
don't bother anything, or can be dissipated. Lots of smaller cores are 
handy for this too, especially the split-toroid (or box) types that are 
commonly used and encountered on cords and internal wiring for EMC noise 
suppression. These are commonly called "prayer beads," for good reason.


I'll have more to say about all this next time.

Regarding your SA, you won't really need it to make any measurements on 
the DC output, until maybe later. The best use will be to look at the CM 
currents via the probe/transformer, which is an isolated AC measurement, 
and will have protection (I'll explain if necessary) against excessive 
signal power.


If you already know about thoroughly protecting your 50 ohm gear when 
making any measurements with DC present, then good. Just in case, I've 
included a couple of links to recent pertinent discussions in the hp and 
tek groups. This subject comes up every so often, and I always have 
something to say about it. Please read both threads all the way up and 
down, for context, and you'll have a pretty good idea of what's involved.


https://groups.io/g/HP-Agilent-Keysight-e quipment/message/106348

https://groups.io/g/TekScopes/message/166344

That's all for now. Good luck in finding lots of good ferrites, and 
maybe even a nice current probe.


Ed

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Re: [time-nuts] potential low-RFI power supply

[jimlux]

On 5/18/20 11:27 AM, Taka Kamiya via time-nuts wrote:

I bought one the moment information about this PS was posted here.

Will you gentlemen come up with a testing method?  I have an audio FFT, 
spectrum analyzer up to 26.5GHz, O'scope of various kind, measuring receiver, 
frequency counters, 6 1/2 DMM and other assorted stuff to play with.  I, 
however, lack the experience and technique most of folks here have.
I'll be glad to run any test and post a result.


Ed Breya had a pretty comprehensive list.

What I would start with is getting some big resistors to serve as a load.



---
(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG
  


 On Monday, May 18, 2020, 1:49:04 PM EDT, jimlux  
wrote:
  
  On 5/18/20 10:19 AM, Joseph Gwinn wrote:

On Mon, 18 May 2020 12:00:02 -0400, time-nuts-requ...@lists.febo.com
wrote:
Re: time-nuts Digest, Vol 190, Issue 30


Message: 1
Date: Sun, 17 May 2020 12:53:42 -0600
From: Eric Scace 
To: Time Nuts email list 
Subject: [time-nuts] potential low-RFI power supply
Message-ID: 
Content-Type: text/plain;    charset=utf-8

Pro Audio Engineering announced a sale (through Friday) on its
nominal 14 Vdc 4A switching supply
.
The test results

webpage compares noise on the DC output and noise frequency spectrum
under a variety of conditions with a lead-acid battery, an Astron
linear supply, and a variety of switching supplies from other
manufacturers.

I have not used this and can?t vouch for its performance. Given
recent discussions here on supplies, the analysis might be
interesting. At least the supplier has attempted to quantify the
performance of its power supply and make that information available
to the prospective purchaser.

It would be interesting to see comparable (or more suitable)
measurements made by others posted here.


Given that this power supply is intended for audio applications such as
mixer boards, if the switching frequency exceeds say 200 KHz, none of
the ripple spurs will matter, as they are far above the band.  Hmm.
Unless that get too close to the sampling rate of some delta-sigma
converter I suppose.


Actually, it's intended as a power supply for HF transceivers, so noise
in the HF band is of interest. Especially if it's radiated from the
power cable.

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Re: [time-nuts] time-nuts Digest, Vol 190, Issue 30

[Dave B via time-nuts]

Hi.

They call them "Low" noise, not No noise!  If you want/need the latter,
then it's a linear regulated supply, or battery.

Also sceptical that the "review" is hosted on the same site that is
selling them...

Look at the figures, for the same conditions, they tell the story, as do
the spectrum plots.

And as for that Astron regulator "ringing" when the load does a step
drop, that's not good.

No affiliation either way, just saying..

73.

Dave G0WBX (a KX3 owner.)

On 18/05/2020 17:00, time-nuts-requ...@lists.febo.com wrote:
> Date: Sun, 17 May 2020 12:53:42 -0600
> From: Eric Scace 
> To: Time Nuts email list 
> Subject: [time-nuts] potential low-RFI power supply
> Message-ID: 
> Content-Type: text/plain; charset=utf-8
>
> Pro Audio Engineering announced a sale (through Friday) on its nominal 14 Vdc 
> 4A switching supply 
> . The 
> test results 
>  webpage 
> compares noise on the DC output and noise frequency spectrum under a variety 
> of conditions with a lead-acid battery, an Astron linear supply, and a 
> variety of switching supplies from other manufacturers.
>
> I have not used this and can?t vouch for its performance. Given recent 
> discussions here on supplies, the analysis might be interesting. At least the 
> supplier has attempted to quantify the performance of its power supply and 
> make that information available to the prospective purchaser.
>
> It would be interesting to see comparable (or more suitable) measurements 
> made by others posted here.

-- 
Created on and sent from a Unix like PC running and using free and open source 
software:


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Re: [time-nuts] potential low-RFI power supply

[Taka Kamiya via time-nuts]

I bought one the moment information about this PS was posted here.  

Will you gentlemen come up with a testing method?  I have an audio FFT, 
spectrum analyzer up to 26.5GHz, O'scope of various kind, measuring receiver, 
frequency counters, 6 1/2 DMM and other assorted stuff to play with.  I, 
however, lack the experience and technique most of folks here have.
I'll be glad to run any test and post a result.
--- 
(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG
 

On Monday, May 18, 2020, 1:49:04 PM EDT, jimlux  
wrote:  
 
 On 5/18/20 10:19 AM, Joseph Gwinn wrote:
> On Mon, 18 May 2020 12:00:02 -0400, time-nuts-requ...@lists.febo.com
> wrote:
> Re: time-nuts Digest, Vol 190, Issue 30
> 
>> Message: 1
>> Date: Sun, 17 May 2020 12:53:42 -0600
>> From: Eric Scace 
>> To: Time Nuts email list 
>> Subject: [time-nuts] potential low-RFI power supply
>> Message-ID: 
>> Content-Type: text/plain;    charset=utf-8
>>
>> Pro Audio Engineering announced a sale (through Friday) on its
>> nominal 14 Vdc 4A switching supply
>> .
>> The test results
>> 
>> webpage compares noise on the DC output and noise frequency spectrum
>> under a variety of conditions with a lead-acid battery, an Astron
>> linear supply, and a variety of switching supplies from other
>> manufacturers.
>>
>> I have not used this and can?t vouch for its performance. Given
>> recent discussions here on supplies, the analysis might be
>> interesting. At least the supplier has attempted to quantify the
>> performance of its power supply and make that information available
>> to the prospective purchaser.
>>
>> It would be interesting to see comparable (or more suitable)
>> measurements made by others posted here.
> 
> Given that this power supply is intended for audio applications such as
> mixer boards, if the switching frequency exceeds say 200 KHz, none of
> the ripple spurs will matter, as they are far above the band.  Hmm.
> Unless that get too close to the sampling rate of some delta-sigma
> converter I suppose.

Actually, it's intended as a power supply for HF transceivers, so noise 
in the HF band is of interest. Especially if it's radiated from the 
power cable.

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Re: [time-nuts] potential low-RFI power supply

[jimlux]

On 5/18/20 10:19 AM, Joseph Gwinn wrote:

On Mon, 18 May 2020 12:00:02 -0400, time-nuts-requ...@lists.febo.com
wrote:
Re: time-nuts Digest, Vol 190, Issue 30


Message: 1
Date: Sun, 17 May 2020 12:53:42 -0600
From: Eric Scace 
To: Time Nuts email list 
Subject: [time-nuts] potential low-RFI power supply
Message-ID: 
Content-Type: text/plain;   charset=utf-8

Pro Audio Engineering announced a sale (through Friday) on its
nominal 14 Vdc 4A switching supply
.
The test results

webpage compares noise on the DC output and noise frequency spectrum
under a variety of conditions with a lead-acid battery, an Astron
linear supply, and a variety of switching supplies from other
manufacturers.

I have not used this and can?t vouch for its performance. Given
recent discussions here on supplies, the analysis might be
interesting. At least the supplier has attempted to quantify the
performance of its power supply and make that information available
to the prospective purchaser.

It would be interesting to see comparable (or more suitable)
measurements made by others posted here.


Given that this power supply is intended for audio applications such as
mixer boards, if the switching frequency exceeds say 200 KHz, none of
the ripple spurs will matter, as they are far above the band.  Hmm.
Unless that get too close to the sampling rate of some delta-sigma
converter I suppose.


Actually, it's intended as a power supply for HF transceivers, so noise 
in the HF band is of interest. Especially if it's radiated from the 
power cable.


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Re: [time-nuts] potential low-RFI power supply

[Bob kb8tq]

Hi



> On May 18, 2020, at 1:19 PM, Joseph Gwinn  wrote:
> 
> On Mon, 18 May 2020 12:00:02 -0400, time-nuts-requ...@lists.febo.com 
> wrote:
> Re: time-nuts Digest, Vol 190, Issue 30
> 
>> Message: 1
>> Date: Sun, 17 May 2020 12:53:42 -0600
>> From: Eric Scace 
>> To: Time Nuts email list 
>> Subject: [time-nuts] potential low-RFI power supply
>> Message-ID: 
>> Content-Type: text/plain;charset=utf-8
>> 
>> Pro Audio Engineering announced a sale (through Friday) on its 
>> nominal 14 Vdc 4A switching supply 
>> . 
>> The test results 
>>  
>> webpage compares noise on the DC output and noise frequency spectrum 
>> under a variety of conditions with a lead-acid battery, an Astron 
>> linear supply, and a variety of switching supplies from other 
>> manufacturers.
>> 
>> I have not used this and can?t vouch for its performance. Given 
>> recent discussions here on supplies, the analysis might be 
>> interesting. At least the supplier has attempted to quantify the 
>> performance of its power supply and make that information available 
>> to the prospective purchaser.
>> 
>> It would be interesting to see comparable (or more suitable) 
>> measurements made by others posted here.
> 
> Given that this power supply is intended for audio applications such as 
> mixer boards, if the switching frequency exceeds say 200 KHz, none of 
> the ripple spurs will matter, as they are far above the band.  Hmm.  
> Unless that get too close to the sampling rate of some delta-sigma 
> converter I suppose.

If it was only that simple …..

Switchers go into a variety of modes depending on what state they are in. 
One common mode “burps” the output when the load current is low. This 
significantly improves efficiency. It also takes the “crud frequency” way down. 

We often use one of these devices at a load well below the rated max. That
makes getting into these sorts of modes a fairly common thing. 

Bob


> 
> Joe Gwinn
> 
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Re: [time-nuts] potential low-RFI power supply

[Joseph Gwinn]

On Mon, 18 May 2020 12:00:02 -0400, time-nuts-requ...@lists.febo.com 
wrote:
Re: time-nuts Digest, Vol 190, Issue 30

> Message: 1
> Date: Sun, 17 May 2020 12:53:42 -0600
> From: Eric Scace 
> To: Time Nuts email list 
> Subject: [time-nuts] potential low-RFI power supply
> Message-ID: 
> Content-Type: text/plain; charset=utf-8
> 
> Pro Audio Engineering announced a sale (through Friday) on its 
> nominal 14 Vdc 4A switching supply 
> . 
> The test results 
>  
> webpage compares noise on the DC output and noise frequency spectrum 
> under a variety of conditions with a lead-acid battery, an Astron 
> linear supply, and a variety of switching supplies from other 
> manufacturers.
> 
> I have not used this and can?t vouch for its performance. Given 
> recent discussions here on supplies, the analysis might be 
> interesting. At least the supplier has attempted to quantify the 
> performance of its power supply and make that information available 
> to the prospective purchaser.
> 
> It would be interesting to see comparable (or more suitable) 
> measurements made by others posted here.

Given that this power supply is intended for audio applications such as 
mixer boards, if the switching frequency exceeds say 200 KHz, none of 
the ripple spurs will matter, as they are far above the band.  Hmm.  
Unless that get too close to the sampling rate of some delta-sigma 
converter I suppose.

Joe Gwinn

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Re: [time-nuts] Baseline measurement with different standard. (same timebase for clock and DUT)

[Bob kb8tq]

Hi

Without seeing the actual data (and setup) there is a lot of guessing in this.

1) Counter floor ADEV plots *should* all have the same slope. They are a 
straight 
line until the hit some sort of basic limit. Often this can be the temperature 
in the 
room impacting the front end delay or something similar.

2) Things like level do count in all this. Trigger levels, signal levels …. 
impact what
you are going to get. If one source is lower level than another …you may get a 
different result. The same also applies to edge rates on PPS signals. 

3) If you are comparing a 10 MHz to a PPS, how you generate the PPS can matter.
Noise in that process can impact the result. 

Those are the top two guesses, there are a lot of other possibilities. The SRS 
620
does some really odd things in this regard ….

Bob

> On May 17, 2020, at 10:36 PM, Taka Kamiya via time-nuts 
>  wrote:
> 
> I hear a term equipment noise, base line noise, and noise floor of the 
> equipment all the time. I had a few concerning and unexpected result with 
> recent tests so I've conducted tests of testing methods.  I'd like to verify, 
> my understanding of the situation is correct.  I basically did baseline test 
> of the same interval counter with different time standards.
> 
> I took an adev measurement of my time-interval counter using standard-A for 
> both clock and input.I took another adev measurement using the same 
> time-interval counter using standard-B for both clock and input.I repeated 
> the same test with standard-C.Run time was 1 hour and interval was 1 second.  
> 
> Method of measurement was, time stamping interval measurement (OK, it was a 
> TICC), clock was 10MHz and input A was fed with 1 pps from the same source.
> Each represents Cesium, Rubidium, and GPSD.
> My expectation was, I will get an over-lapping (right on top of each other) 
> with very minor variations.  Since clock and the DUT was the same, why would 
> there be any different
> Surprising result (to me) was that they all started with different Adev value 
> (origin) and sloped downwards at the slope -a (same value).  They were 
> EXACTLY parallel from 1 second all the way to the end (which was 900 seconds 
> but run time was 1 hour).  
> 
> What did I just do?  How can I make use of this graph?  Why are they all the 
> same slope?  Why are they not overlapping?
> I can assume one of the answers to be, clock and the TICC form an "equipment" 
> and that line represents the base line FOR THAT standard.  That's as far as I 
> can get.  If I can get a better explanations, I would very much like to hear 
> it.  I also wonder if this would be the same situation for every counter and 
> every method, but I can do that test later.
> Thank you.
> 
> 
> --- 
> (Mr.) Taka Kamiya
> KB4EMF / ex JF2DKG
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[time-nuts] Free courses from the National Physical Laboratory (NPL)

[Dr. David Kirkby]

NPL do a number of courses. Some are available online, some only in a
class. The online ones can cost up to £700 (GBP). However, these are free
until the end of June

https://www.npl.co.uk/skills-learning/free-e-learning

For anyone interested in metrology, there are a lot of relevant courses.
Some are at quite an advanced level.

For the vast majority of the courses there’s an exam at the end with a 50%
passmark. I don’t think the certificates will of any use to me, but it
added a challenge.

I completed the “Introduction to Measurement and Metrology” course. I
erroneously believed that the course was supposed to be 1-day, but there
seemed to be a lot for a 1-day course. Later I realised it was supposed to
be 0.5 days! I guess I am just a slow learner.

The bit that took my largest amount of time to commit to memory was the
roles of the BIPM, CGPM, CIPM, NMI, RMOs etc in disseminating the SI
units.  I must have watched the video on that ten times before I was
confident I had a reasonably good understanding of that.

The 40 minutes for the exam was more than enough time.

Dave.


-- 
Dr. David Kirkby,
Kirkby Microwave Ltd,
drkir...@kirkbymicrowave.co.uk
https://www.kirkbymicrowave.co.uk/
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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