.....but can you listen to the radio in the car ??  Many of these things
will kill other applications like broadband over twisted pair and PLT tv
extension. Never mind killing you!
Alan
G3NYK
----- Original Message -----
From: "Van Horn, David" david.vanhorn@backcountryaccess.com
To: "Discussion of precise time and frequency measurement"
time-nuts@febo.com
Sent: Thursday, October 13, 2016 2:05 PM
Subject: Re: [time-nuts] For those that insist on using switching power
supplies

Not quite. They power the device in question while they’re charging the battery. Now, I’ll admit that powering a phone is a much lower bar than powering, say, an audio amplifier, but I’d also say that some of the devices on that page were pumping out way more garbage than even any digital system should have to put up with.

Well, there’s some of that, but the worst offenders were counterfeit devices that were pumping out unreasonable levels. To your analogy, they were the outer shell of a family car with a the engine from an Edsel installed in it without a muffler or any emissions controls fed from an open bucket of gasoline sitting on the passenger’s seat.

Actually, if they have the "CE" stamp on the product, then they have very
specific radio interference limits that they must test and meet.
It must have been tested, certified, and the certification package
available for inspection.

Whether they actually met it, then pulled the interference supression parts
off the board as a "cost reduction" as is common in no-name computer power
supplies, or whether it never met it to begin with, is for you to
speculate.  Some suppliers will explain to you that "CE" means China
Export, not that it meets the consolidated European safety and electrical
rules.

--- Graham

On Thu, Oct 13, 2016 at 5:25 PM, Nick Sayer via time-nuts <
time-nuts@febo.com> wrote:

Even if they meet the CE or FCC requirements for unintentional
radiators, they can still screw up the short wave bands and more; many
are bad enough that I can see the noise they emit on an oscilloscope
with a shorted probe.  At least in the US, there are a lot of cheap
products with switching regulators which cause problems including CFL
and LED lamps and FCC enforcement is poor.

That confusion between the European Economic Area CE and the China
Export CE is just shrewd.

On Thu, 13 Oct 2016 17:57:02 -0500, you wrote:

On Thu, 13 Oct 2016 20:07:41 -0500
David davidwhess@gmail.com wrote:

It's an outright lie
https://en.wikipedia.org/wiki/CE_marking#China_Export

		Attila Kinali

--
Malek's Law:
Any simple idea will be worded in the most complicated way.

Benchtop linear power supplies also share in some deceptive marketing
regarding noise. Some have horrible 1/f noise, others are on par to a
tl431, which isn't too bad. Some will have spurious tones 10's of dB above
the Gaussian noise spectrum. Unfortunately most linear power supplies only
spec a total rms noise over 20 Hz - 20 MHz. Whether that's a flat power
spectrum or a handful of tones, is a test it and see senario.

On Wednesday, 12 October 2016, Pete Lancashire pete@petelancashire.com
wrote:

On Thu, Oct 13, 2016 at 6:05 AM, Van Horn, David
david.vanhorn@backcountryaccess.com wrote:

Not only that but,  the 5 volts comping out of the larger is almost
certainly the input to another DC/DC power supply and NOT used
directly.
You can't charge a Lithium battery with the 5 volts the charger outputs.

If you don't know about LiPo batteries, they need a constant current
power source and then as they get close to charged the charger
switches to constant voltage (VERY roughly) at about 4V per cell.

I have a project right here on my desk as I type.  I'm using the
output of a generic USB hub.  The circuit is  a cap from 5V to GND and
then a low dropout regulator to get 3.3 volts.    I don't care to much
if there is huge ripple on the 5.0 volts coming in as long as it stays
above the LDO limit.

Also it looks like they tested the USB chargers with no load.  A
typical load might have a say, 0.01uf cap to short the noise to
ground.  So in use the power might be better?

It was no surprise the counterfeit chargers were horrible.  The
manufacturers are by definition of "counterfeit" being dishonest slim
balls. Why would he care about anything other then that he can fool
some people into buying his product.  There are third party chargers
that are not trying to copy a well known brand, these are usually much
better

--

Chris Albertson
Redondo Beach, California

How would one go about testing power supplies and seeing how noisy they are?  I have the standard suite of tools, an oscilloscope and a little (dangerous) know-how.  I am just not sure what to look for or how to safely hook it up to test.

Thanks in advance for any tips!

-Randal R.
	(at CubeCentral)

-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces@febo.com] On Behalf Of Chris Albertson
Sent: Friday, 14 October, 2016 02:29
To: Discussion of precise time and frequency measurement time-nuts@febo.com
Subject: Re: [time-nuts] For those that insist on using switching power supplies

On Thu, Oct 13, 2016 at 6:05 AM, Van Horn, David david.vanhorn@backcountryaccess.com wrote:

Not only that but,  the 5 volts comping out of the larger is almost certainly the input to another DC/DC power supply and NOT used directly.
You can't charge a Lithium battery with the 5 volts the charger outputs.

If you don't know about LiPo batteries, they need a constant current power source and then as they get close to charged the charger switches to constant voltage (VERY roughly) at about 4V per cell.

I have a project right here on my desk as I type.  I'm using the output of a generic USB hub.  The circuit is  a cap from 5V to GND and
then a low dropout regulator to get 3.3 volts.    I don't care to much
if there is huge ripple on the 5.0 volts coming in as long as it stays above the LDO limit.

Also it looks like they tested the USB chargers with no load.  A typical load might have a say, 0.01uf cap to short the noise to ground.  So in use the power might be better?

It was no surprise the counterfeit chargers were horrible.  The manufacturers are by definition of "counterfeit" being dishonest slim balls. Why would he care about anything other then that he can fool
some people into buying his product.  There are third party chargers
that are not trying to copy a well known brand, these are usually much better

--

Chris Albertson
Redondo Beach, California

time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Hi

A spectrum analyzer and some sort of active load are generally the two pieces of gear I reach for
first when testing supplies. You need an analyzer that will cover the entire “range of interest” for
the supply or possibly multiple analyzers if that turns out to be 0.1 Hz to 6 GHz. Since noise changes
with load, whatever you do needs to be repeated at various output levels on the supply.

Bob

Set your scope for AC coupling. Set your scope probe for 1x rather than 10x. Use the absolutely shortest scope grounding you can. That’s what those spring looking things that came with it are for. I typically use the spring gizmo and probe on an SMD cap. The ground wire with an alligator clip will just pick up far more noise than you’ll be measuring. This is how I was able to measure the noise and ripple of the SC189Z switcher feeding the OCXO in my GPSDO. I got measurements of ~4 mV P-P that way. Be careful you don’t get the probe and ground reversed - your scope won’t likely have an isolated ground from your DUT and that would therefore be bad.

You’re going to want to check the supply’s performance under load. For that, you’ll may want to get yourself a dummy load. I got one from Tindie for testing my Pi Power design: https://www.tindie.com/products/arachnidlabs/reload-2/

Nick, thanks for your detailed reply.  Would you happen to have a photo of the "spring looking things?"  I am not entirely sure I have one of those included with the kit that came with the scope.
What size of capacitor would you suggest?
I happen to have the exact same dummy load that you do.  I have added on a fan for higher current/longer use.

Thanks for the help, I look forward to trying out some of the measurements that I've seen posted elsewhere ( such as this link: http://www.righto.com/2012/10/a-dozen-usb-chargers-in-lab-apple-is.html )

Cheers!

-Randal R.
	(at CubeCentral)

-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces@febo.com] On Behalf Of Nick Sayer via time-nuts
Sent: Friday, 14 October, 2016 12:17
To: Discussion of precise time and frequency measurement time-nuts@febo.com
Subject: Re: [time-nuts] For those that insist on using switching power supplies

Set your scope for AC coupling. Set your scope probe for 1x rather than 10x. Use the absolutely shortest scope grounding you can. That’s what those spring looking things that came with it are for. I typically use the spring gizmo and probe on an SMD cap. The ground wire with an alligator clip will just pick up far more noise than you’ll be measuring. This is how I was able to measure the noise and ripple of the SC189Z switcher feeding the OCXO in my GPSDO. I got measurements of ~4 mV P-P that way. Be careful you don’t get the probe and ground reversed - your scope won’t likely have an isolated ground from your DUT and that would therefore be bad.

You’re going to want to check the supply’s performance under load. For that, you’ll may want to get yourself a dummy load. I got one from Tindie for testing my Pi Power design: https://www.tindie.com/products/arachnidlabs/reload-2/

time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

It is also wise to measure the noise floor of the test setup as fully
connected as possible. For one of those usb charger cubes, you can use a
power bar with a power switch (which will only switch the hot line on/off,
earth and neutral are permanently connected, one would hope). You will see
a lot of other noise sources before you even power up your DUT.

On Fri, Oct 14, 2016 at 2:16 PM, Nick Sayer via time-nuts <
time-nuts@febo.com> wrote:

I don’t have a picture, but the Internet does: http://i.stack.imgur.com/PSo3N.jpg

Well, I use mostly 0805 MLCCs on my boards, not counting the occasional polymer or electrolytic.

On Fri, Oct 14, 2016 at 11:00 AM, Cube Central cubecentral@gmail.com wrote:

You'd ned a spectrum analyser.    You could assemble one from parts
that are used for Software Radios.  A USB TV tunnel dongle and a
computer and a good mixer and clean oscillator.  With hat you'd be
able to characterize noise from DC to about 900MHz

Those with more money than time would just spend the bucks to buy an SA

Those who don't need numbers would just look at the DC on a scope and
"eye ball it" and say "wow that is noisy" or "wow that looks clean"

In all cases you'd want to put a realistic load on the power supply.
But what is that? I bet if varies a lot.

And like I wrote before it may not even matter as phones don't
directly use the 5 volt DC that these chargers produce.

Chris Albertson
Redondo Beach, California

A basic DSO has maybe 300 uVrms noise over 100 MHz bandwidth, which is a
spectral noise floor of 30 nV/rtHz (assuming a brick-wall filter), if your
DUT is quieter than that you can always add an LNA.

On Fri, Oct 14, 2016 at 2:59 PM, Chris Albertson albertson.chris@gmail.com
wrote:

On Fri, 14 Oct 2016 12:00:08 -0600
"Cube Central" cubecentral@gmail.com wrote:

There are different frequency ranges one looks at when measuring
power supplies:

1. Long term stability over seconds to hours
2. Low frequency noise between 0.1Hz and 10Hz
3. Mid frequency noise between 10Hz and 20MHz
4. High frequency noise beyond 20MHz

The borders of these different ranges of noise are kind of arbitrary
and different people use different values. They are motivated by the
need of the consumer (of power) and by the limitations of different
measurement equipment.

The long term stability is what we usually call "wander" and
is mostly dominated by the thermal stability and aging of the
power supply's voltage reference and its control loop. To measure
it correctly one usually uses a high resolution DMM in the 7.5
or 8.5 digits range. One can also build a homebrew system using
a high resolution ADC (like 32bit delta-sigma converters: AD7177-2,
LTC2508-32, AD1262) and a very stable voltage reference (LTZ1000, LM399).
I'd like to refer to the volt-nuts mailinglist on how to properly
do this, as my knowledge in this area is rather limited.

The low frequency range is what we usually call the 1/f region,
although the long term stability also belongs to it. But unlike
the long term region you don't have to sacrifice a virgin to
get decent measurment data. Jim William's appnote[1] has lots of
details how to measure noise in this region. There are slightly
more modern circuits by Todd Owen/Amit Patel[2] and Gerhard Hoffmann[3].
I recently stumbled over a similar amplifier by Enrico Rubiola
and Franck Lardet-Vieudrin[4]. Both [4] and [5] explain why for
low impedance sources (like power supplies) a BJT input stage
would be a better choice than jFETs and also cover the influence
of temperature on the measurement. [6] gives some additional info
on how to design the differential input stage.
I wonder how an active offset voltage cancelation scheme for
the differential pair input stage using one of the chopper stabilized
opamps (eg LTC2057) would change the temperature dependence and long
term stability  (aka 1/f^a noise) of the circuit, but I have not seen
any measurements of a system like this yet.

The mid frequency range is mostly influenced by the telecom
noise requirements, which for historical reasons cover the 10Hz
to 20MHz range. It is probably the easiest region to measure
with homebrewn instruments. A decently fast ADC with a low
noise voltage reference (like the LTC6655) are all you need.
Depending on how accurately you want to measure the noise, it makes
sense to further split this range into a lower range up to ~500kHz
and an upper range above 500kHz. The reason is that there are today
several high resolution ADCs available that support sampling rates of
up to 1Msps (and some beyond),eg:
AD7982, 18bit 1Msps
AD7984, 18bit 1.33Msps
AD7960, 18bit 5Msps
LTC2386-18, 18bit 10Msps
LTC2378-20, 20bit 1Msps
LTC2368-24, 24bit 1Msps
These would allow to accurately measure the noise range that is
IMHO most interesting for most applications. Interesting because
a lot of applications are insensitive to noise below 1Hz or even
below 10Hz and noise above several 100kHz becomes easy to filter
out using inductors, ferrit beads and ceramic capacitors. When
choosing an ADC for this range make sure you check the actual
SNR/SFDR performance as it a higher output resolution not necessarily
corresponds to the actual performance delivered. This becomes
especially pronounced when going higher with the sampling rate
to cover the higher noise frequency ranges. Beyond 5-10Msps 16bit
is the best you can get and conversly the SNR is limited to
something around 90dB-95dB.

The high frequency noise, I mentioned above 20MHz, but probably
the limit is more in the 1-10MHz range, is where radiation
becomes interesting. Ie with increasing frequency it becomes
harder and harder to "isolate" electronics against noise
and it becomes necessary to shield it with metal plates.
This range is important for the switched power supplies that
started this thread. These supplies have usually switching
frequencies between a couple of 10kHz to low 100kHz for high
power and AC/DC supplies and goes up to a few MHz for the low
power (where low power is relative and can be several W) low
voltage DC/DC supplies. And as these supplies are switching hard
they produce lots of harmonics. A badly designed supply can easily
produce very noticable spikes at 100MHz. Measuring this type of
noise is probably easiest with a good digital oscilloscope with
a sufficiently high analog bandwidth and sampling rate. Alternatively
specturm analysers are a good choice too. Going homebrew in this
range is kind of difficult, as high resolution ADCs max out around
100-125Msps, with the odd exception of LTC2107 that gives 16bit up
to 210Msps (and still an 80dB SNR). Ie the maximum achievable
bandwidth is 40-90MHz for single ADC configurations. But interfacing
these high-speed ADCs requires an FPGA and thus considerable effort.
An alternative approach is to build a spectrum analyser like setup
with a tunable oscillator and a down-mixer. The problem here would
then be to get a flat frequency response and the required calibration.
Another approach is to use an SDR system with a low lower frequency
limit, but this also requires to kind of calibrate it as these are
not ment for power measurements and thus their frequency response
is not really flat. But they give at least a good indication whether
you have any spikes that stick far out.

One thing I haven't mentioned yet is that you will need to have some
form of load that can be switched. Power supply noise is highly dependent
on the current flow, especially for switched power supplies. But
because the load will also create noise, you probably want to just
have a bank of relay switched power resistors. In case you want to
measure the response on load switches, you should replace the relays
by power transistors (otherwise the bouncing of the relay will
confound the measurement).

		Attila Kinali

[1] "775 Nanovolt Noise Measurement for A Low Noise Voltage Reference",
by Jim williams, Linear AN124, 2009
http://www.linear.com/docs/28585

[2] "Measuring 2nV/sqrt(Hz) Noise and 120dB Supply Rejection
on Linear Regulators", by Todd Owen and Amit Patel, Linear AN159, 2016
http://www.linear.com/docs/47682

[3] "A 220 pV/sqrt(Hz) low noise preamplifier", by Gerhard Hoffman, 2014
http://www.hoffmann-hochfrequenz.de/downloads/lono.pdf

[4] "Low Flicker-Noise DC amplifier for 50Ω Sources", by Enrico Rubiola
and Franck Lardet-Vieudrin, 2004
http://rubiola.org/pdf-articles/journal/2004rsi(rubiola)low-flicker-dc-amplifier.pdf
http://arxiv.org/abs/physics/0503012

[5] "Some Considerations for the Construction of Low-Noise Amplifiers in
Very Low Frequency Region", by Sikula, Hashiguchi, Ohki, Tacano. 2004
http://dx.doi.org/10.1007/1-4020-2170-4_27

[6] "Some Tips on Making a FETching Discrete Amplifier", by George Alexandrov
and Nathan Carter, Analog Dialog 47-10, 2013
http://www.analog.com/library/analogdialogue/archives/47-10/discrete_amplifier.html

--
Malek's Law:
Any simple idea will be worded in the most complicated way.

I have done this and it works great; the breakpoint between the
chopper amplifier and the low noise amplifier can be adjusted to
combine the wideband noise from the low noise amplifier and the 1/f
noise and drift of the chopper amplifier.

Jim Williams wrote a couple of different application notes where this
was used with both integrated and discrete amplifiers.

On Sat, 15 Oct 2016 00:53:25 +0200, you wrote:

On Fri, 14 Oct 2016 22:25:55 -0500
David davidwhess@gmail.com wrote:

Yes, there are several appnotes and papers that list this method.
But I am not aware of any noise measurement below 0.1Hz for such
an amplifier setup.

		Attila Kinali

--
It is upon moral qualities that a society is ultimately founded. All
the prosperity and technological sophistication in the world is of no
use without that foundation.
-- Miss Matheson, The Diamond Age, Neil Stephenson

On Tue, 18 Oct 2016 11:27:05 +0200, you wrote:

Below 0.1 Hz it is not all that interesting; the noise is just the
noise of the chopper amp and flat below the chopping frequency.  I
think Jim Williams mentioned in one of his articles that at low
frequencies, noise and drift are effectively the same thing so thermal
EMF becomes a large if not the largest contributor.

When I did it, I extended the single ended design to a fully
differential gain of 1000 amplifier using a pair of LT1028s with a
pair of LTC1150s for correction.  I used the noise curves to estimate
what the integrator gain should be and after adjusting it for minimum
noise from about 0.1 to 10 Hz, it was very close to the actual
crossover point in the datasheet specifications.  RMS noise was
measured by taking the standard deviation of the DC values from a
Fluke 8505A over 10 seconds.

Hoi David,

On Tue, 18 Oct 2016 05:25:35 -0500
David davidwhess@gmail.com wrote:

Depends on what you are doing ;-)

Yes, different words for the same thing.

Ah.. good to know. Thanks!
Any guess what the other big factors are?

You wouldn't have the schematics and the measurments available somewhere?
It would be interesting to have a look at them.

BTW: Should this discussion be moved over to volt-nuts?
I kind of feel we are getting too off-topic for time-nuts.
(though my interest comes from long term time measurment)

		Attila Kinali

--
It is upon moral qualities that a society is ultimately founded. All
the prosperity and technological sophistication in the world is of no
use without that foundation.
-- Miss Matheson, The Diamond Age, Neil Stephenson

On Tue, 18 Oct 2016 14:52:15 +0200, you wrote:

Over time scales of 100s of milliseconds to seconds, the self heating
and temperature coefficient of the feedback network resistors causes
errors which extend settling time and look like low frequency noise.
At this level, self heating also contributes to non-linearity.

Intermodulation between frequency components of the signal close to
the chopping frequency can result in low frequency noise.  Modern
integrated chopper amplifiers do various things to prevent this so I
do not think it is a problem now.

External thermal effects are the big problem though.  Jim Williams
discusses this in Linear Technology application note 9 and includes
measurements showing noise down below 0.01 Hz.  He also discusses
other sources of noise:

http://www.linear.com/docs/4105

I may have them and my notes from more than 10 years ago but I could
redraw the schematic from memory and describe it well enough to
duplicate; the design is not complicated.  I got the basic idea from
figure 14 on page 10 Linear Technology application note 21:

http://www.linear.com/docs/4116

Mirror the standard high input impedance non-inverting amplifier
configuration top to bottom to produce a 2 operational amplifier (4 in
this case) differential amplifier.  The symmetry in the circuit helps
balance noise sources like thermocouples.  I do not remember if
synchronizing the clocks of the chopper stabilized amplifiers improved
performance but if it did, the difference was not large at least with
LTC1050s and LT1028s.

The part I found amazing when I worked with this circuit is everything
worked just as theory predicted; the calculated integrated noise level
was just about right and the crossover frequency between the
amplifiers matched the datasheet specifications.  The low frequency
noise was so low that I could measure resistance just from its low
frequency Johnson noise which scared me.

The original non-inverting circuit would be suitable for use in the
signal chain driving the voltage control input of a crystal oscillator
preserving low noise and low drift from the DAC.  Replace the low
noise precision bipolar operational amplifier with a low noise low
input bias current operational amplifier and it might be useful for
implementing long time constant filters in an analog GPSDO design
although I suspect sacrificing input bias current (the chopper input
bias current is relatively high) for this level of precision and low
frequency noise may not be a worthwhile trade off.

Am Thu, 13 Oct 2016 17:57:02 -0500
schrieb "Graham / KE9H" ke9h.graham@gmail.com:

Umm, I guess most of us wish it was actually like that. Strictly
speaking, the CE sign legally is no more than a statement by the
manufacturer that he believes this very product conforms to the
applicable rules ans regulations. This does not imply any testing by
itself. It's more of an self assessment, which could also be based on
gut feeling and customer requirements ("must have CE sign").

Testing is not required to carry the CE mark. Yes, of course, the CE
mark implies that the product meets various requirements, out of which
some can only be guaranteed through testing, but this is often
overlooked.

The more honest scumbags will just claim this very device was not
intended to be sold outside of China and they don't have the logistics
to produce enclosures with different labeling.

How much of this is considered close to truth depends on those who do
consider. As long as all those smallish shops in Shenzhen are not
faced by prosecution, this won't change, and China does not seem keen
on changing this.

Best regards,
Florian