Re: [time-nuts] Recommendations for Mains Power Monitor / Logger

[Magnus Danielson]

Hi,

On 03/11/2018 11:25 PM, Tom Van Baak wrote:
>> In short, the GPS to UTC time correction polynomial got screwed up.
> 
> Yes, that was an exciting time!

> As far as monitoring mains phase -- a 13 microsecond step would be lost in 
> the normal jitter and drift of power line timing. My 60 Hz logging was 
> unaffected by the event because I use a cesium reference (not GPS or GPSDO).

The powergrid folks saw it!

There where some hilarious things happening.

Cheers,
Magnus
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Re: [time-nuts] Recommendations for Mains Power Monitor / Logger

[Bob kb8tq]

Hi

If you pick the “right” STM board, it can handle processing up around 
a megasample. It’s internal ADC’s are more of an issue than the sample
rate. You can only do just so well on harmonics with a 12-ish bit ADC.
Even if you go crazy and get one with a display, they still are pretty cheap.

Bob

> On Mar 11, 2018, at 6:13 PM, Attila Kinali  wrote:
> 
> On Sun, 11 Mar 2018 14:41:23 -0500
> Dana Whitlow  wrote:
> 
>> I'll have to take a look around to see if there isn't something cheap that
>> can run
>> standalone so I don't have to tie up (or wear out) a whole PC for the
>> acquistion
>> process.
> 
> Blub... I should the whole mailsorry about that.
> 
> How about this: get a uC board (e.g. STM32discovery), replace
> the crystal with a 10MHz input from your frequency reference.
> Use the on-chip 12bit (really just 6bit) ADC to sample the
> sine wave from your mains. Do phasor measurement in software.
> 
> Probably any sampling frequency between 200Hz and 1kHz should
> do the job, Which is slow enough so you can still handle the
> samples with the uC alone and don't need any fancy DSP.
> 
> 
>   Attila Kinali
> 
> -- 
>   The bad part of Zurich is where the degenerates
>throw DARK chocolate at you.
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Re: [time-nuts] Recommendations for Mains Power Monitor / Logger

[Tom Van Baak]

> In short, the GPS to UTC time correction polynomial got screwed up.

Yes, that was an exciting time!



For newcomers to the list, the bizarre GPS 13 microsecond jump was a hot topic 
on time-nuts back in 26-Jan-2016. The thread starts with an observation by Paul 
Boven:

https://www.febo.com/pipermail/time-nuts/2016-January/095667.html

And includes detailed follow-up by Martin Burnicki:

https://www.febo.com/pipermail/time-nuts/2016-January/095692.html
https://www.febo.com/pipermail/time-nuts/2016-January/095756.html
https://www.febo.com/pipermail/time-nuts/2016-January/095714.html
https://www.febo.com/pipermail/time-nuts/2016-January/095753.html

If you have time, read the full "GPS jumps of -13.7 us?" thread from the 
archives:

https://www.febo.com/pipermail/time-nuts/2016-January/subject.html#95667

And also the "GPS PRN 32" thread:

https://www.febo.com/pipermail/time-nuts/2016-January/subject.html#95682



As far as monitoring mains phase -- a 13 microsecond step would be lost in the 
normal jitter and drift of power line timing. My 60 Hz logging was unaffected 
by the event because I use a cesium reference (not GPS or GPSDO).

/tvb

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Re: [time-nuts] Recommendations for Mains Power Monitor / Logger

[Attila Kinali]

On Sun, 11 Mar 2018 14:41:23 -0500
Dana Whitlow  wrote:

> I'll have to take a look around to see if there isn't something cheap that
> can run
> standalone so I don't have to tie up (or wear out) a whole PC for the
> acquistion
> process.

Blub... I should the whole mailsorry about that.

How about this: get a uC board (e.g. STM32discovery), replace
the crystal with a 10MHz input from your frequency reference.
Use the on-chip 12bit (really just 6bit) ADC to sample the
sine wave from your mains. Do phasor measurement in software.

Probably any sampling frequency between 200Hz and 1kHz should
do the job, Which is slow enough so you can still handle the
samples with the uC alone and don't need any fancy DSP.


Attila Kinali

-- 
The bad part of Zurich is where the degenerates
throw DARK chocolate at you.
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Re: [time-nuts] Recommendations for Mains Power Monitor / Logger

[Bob kb8tq]

Hi

Cute !!

It certainly beats firing up an R-392 to see if you can get a tick from WWV…

Bob

> On Mar 11, 2018, at 5:42 PM, Tom Van Baak  wrote:
> 
>> “Back in the day” we used WWV and the kitchen clock for that sort of thing……
> 
> Bob,
> 
> Yes, not much has changed. I use multiple methods to measure 60 Hz in order 
> to gain confidence in the results. Besides the picPET, I've used a commercial 
> TrueTime TFDM (Time/Frequency Deviation Meter) and also a plain old kitchen 
> clock (synchronous motor, wall clock).
> 
> Example: I took photos of the kitchen clock precisely 30 seconds after each 
> quarter hour. Here's the short animated GIF of that run; you can see how the 
> wall clock wanders from 0 to 5 seconds ahead of the UTC reference clock (seen 
> in the background):
> 
> http://leapsecond.com/pages/tec/mains-clock-ani.gif
> 
> For alert readers: the +/- 1 second jitter in the reference clock is due to 
> drift and latency in the PC scripts used to trigger the photo capture. Also 
> sunrise (Pacific time) can be seen in the background starting about 1300 UTC.
> 
> /tvb
> 
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Re: [time-nuts] Recommendations for Mains Power Monitor / Logger

[Attila Kinali]

On Sun, 11 Mar 2018 14:41:23 -0500
Dana Whitlow  wrote:

> Now I'm getting interested in this.  My concept is to take the 60 Hz in, do
> reasonable
> HW filtering to knock off the HF junk that commonly rides on the sinewave,
> then use
> an RC quadrature phase splitter to yield I & Q signals.  Then sample at
> 1PPS with
> my Rb's PPS as the sample trigger,  and capture the result with a 2-channel
> data
> acquisition gadget of some sort.  It's that last item that's holding me
> back.

Just get a USB soundcard. feed the left channel with the 50/60Hz
from your mains, and the right channel with some signal between
about 1kHz and 10kHz that you somehow derived from your frequency
standard, then you can do the rest in software on your PC. If you
do not want to code, you can use GnuRadio and use their Labview
like point-and-click interface (yes, GnuRadio can be used for more
than just to look for long lost satellites with oversized antennas ;-).
This way you don't even need a 90° hybrid or anything similarly
temperature sensitive.

Attila Kinali

-- 
The bad part of Zurich is where the degenerates
throw DARK chocolate at you.
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Re: [time-nuts] Recommendations for Mains Power Monitor / Logger

[Tom Van Baak]

> “Back in the day” we used WWV and the kitchen clock for that sort of thing……

Bob,

Yes, not much has changed. I use multiple methods to measure 60 Hz in order to 
gain confidence in the results. Besides the picPET, I've used a commercial 
TrueTime TFDM (Time/Frequency Deviation Meter) and also a plain old kitchen 
clock (synchronous motor, wall clock).

Example: I took photos of the kitchen clock precisely 30 seconds after each 
quarter hour. Here's the short animated GIF of that run; you can see how the 
wall clock wanders from 0 to 5 seconds ahead of the UTC reference clock (seen 
in the background):

http://leapsecond.com/pages/tec/mains-clock-ani.gif

For alert readers: the +/- 1 second jitter in the reference clock is due to 
drift and latency in the PC scripts used to trigger the photo capture. Also 
sunrise (Pacific time) can be seen in the background starting about 1300 UTC.

/tvb

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Re: [time-nuts] Recommendations for Mains Power Monitor / Logger

[Magnus Danielson]

Hi Andy,

On 03/11/2018 08:40 PM, Andy Backus wrote:
> Thank you for your posting, Magnus.
> 
> Your information is very interesting.
> 
> Do you mind saying a little more about the "incident" on 26-JAN-2016?  I 
> don't find reference to it in the link.  And my own TE plot for then shows no 
> obvious disturbance.
> 
> Thanks.

Please read this:
https://rubidium.dyndns.org/~magnus/papers/GPSincidentA6.pdf

In short, the GPS to UTC time correction polynomial got screwed up.

I got email from NASA, ended up having to call NASA HQ and got invited
to Washington DC to present before the US PNT advisory board.

Among the stranger things I've done in my life, but it was fun.

Cheers,
Magnus
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Re: [time-nuts] Recommendations for Mains Power Monitor / Logger

[Andy Backus]

Thank you, Bill.  Your comments on noise I find interesting.


I have tracked the TE of the Western Interconnection for 2-1/2 years now.  For 
reliability's sake I use three separate systems that count in different ways.  
Transients are my biggest problem.  I use low pass filters and optical links 
and clipping zeners.  I blank out counter input for most of the 16.67 msec 
between counts.  Still, I lose count on one or another of the systems every 
once in a while.  There is a lot of junk on the grid.


Andy Backus

Bellingham, WA



From: time-nuts  on behalf of Bill Hawkins 

Sent: Saturday, March 10, 2018 11:40 PM
To: 'Bob Albert'; 'Discussion of precise time and frequency measurement'; 
'Patrick Murphy'
Subject: Re: [time-nuts] Recommendations for Mains Power Monitor / Logger

Well, this synchronization follows the laws of physics. If the energy
generated doesn't equal the energy consumed, then the frequency may
raise or lower. This is for steam turbines. If the energy come front an
inverter from a DC tie line, as it does from the four regions in the US,
the frequency is anything it wants to be. Well not quite. Raising the
inverter frequency a hair causes the tie line to be the major source of
energy. One could track the use of energy by frequency to make
investment decisions in manufacturer's stocks.

The problem with zero crossing triggers is the amount of noise caused by
solid state power supplies and by tap changing by the power companies to
match loads to minimize transmission losses. I've considered using a
mechanical synchronous motor and slotted wheel to eliminate noise near
the zero crossing, but now that I am 80, I don't give a darn, you see.

Bill Hawkins


 -Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob
Albert via time-nuts
Sent: Saturday, March 10, 2018 5:58 PM

 There isn't a whole lot of justification for measuring power line
frequency.  We are all synchronized (in the first world at least) and
while there are phase instabilities, it's seldom the frequency varies
enough to overcome the noise.
As for voltage, it's much more steady than several years ago.  Most
people have 122 Volts, give or take a couple.  Again, not a whole lot of
purpose in recording it.
The distortion is another story.  It's never quite sinusoidal but there
is also some random noise picked up between the generators and the
load.  Looking at the 'scope it's seldom it looks like the textbook
picture of a sine wave.  Chances are most distortion is odd harmonic.
Distortion probably mostly comes from loads which are not resistive,
such as switching power supplies, rectifiers, fluorescent lamps, and
such.  These loads draw currents that are not sinusoids and so cause
voltage drops that are also of that character.
Bob

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Re: [time-nuts] Recommendations for Mains Power Monitor / Logger

[Dana Whitlow]

Now I'm getting interested in this.  My concept is to take the 60 Hz in, do
reasonable
HW filtering to knock off the HF junk that commonly rides on the sinewave,
then use
an RC quadrature phase splitter to yield I & Q signals.  Then sample at
1PPS with
my Rb's PPS as the sample trigger,  and capture the result with a 2-channel
data
acquisition gadget of some sort.  It's that last item that's holding me
back.

I'll have to take a look around to see if there isn't something cheap that
can run
standalone so I don't have to tie up (or wear out) a whole PC for the
acquistion
process.

Dana


On Sun, Mar 11, 2018 at 1:49 PM, Didier Juges  wrote:

> I like the sound card idea. However I believe it's much better to use the
> two channels. At least under Windows, it is much easier to track the
> relative phase of the two channels of one sound card than the absolute
> phase of one channel compared to the system clock.
> I have written an audio VNA in Visual Basic that has all the building
> blocks.
> Unfortunately, it is harder and harder to develop VB 6.0 under Windows 10
> so I am not doing much of that anymore.
> Since I am doing it using FFT, filtering (and harmonics measurements) come
> for free.
>
> On Mar 10, 2018 10:47 PM, "Tom Van Baak"  wrote:
>
> > > I've done some Googling and have found any number of designs.
> >
> > Pat,
> >
> > 1) Safety. I usually use a low voltage step-down transformer. This gives
> > isolation and safety. Anything from 3 VAC to 24 VAC is fine.
> >
> > 2) Trigger. There are dozens of schematics on the web for capturing the
> > zero-crossing of a low-voltage sine wave. You can easily go overboard on
> > this. Or just keep it simple and feed the signal through a resistor
> > directly into a microprocessor input. The internal clamping diodes do
> their
> > thing. A Schmitt trigger input is helpful but not necessary depending on
> > how your software makes the measurement.
> >
> > 3) Timebase. Given the long-term accuracy of mains (seconds a day,
> seconds
> > a year) you don't need an atomic timebase. If you collect data for a
> couple
> > of days any old XO will be fine. If you plan to collect data for months
> you
> > may want a OCXO. Most of us just use cheap GPS receivers.
> >
> > 4) Measurement. There are many ways to measure the signal. You can
> measure
> > frequency directly, as with a frequency counter. You get nice data but it
> > may not be perfect long-term due to dead time or gating effects in the
> > counter.
> >
> > So what most of us do is measure phase (time error) instead. One way is
> to
> > make time interval measurements from a given mains cycle to a GPS 1PPS
> tick
> > or vice versa, from each GPS/1PPS tick to the very next mains cycle.
> Either
> > way you get about sample per second. If you're in search of perfection it
> > gets a bit tricky when the two signals are in a coincidence zone.
> >
> > The other approach is not to use a frequency or time interval counter at
> > all. Instead you timestamp each cycle, or every 60th cycle. Unix-like
> > systems have this capability. See Hal's posting. I use a picPET, a PIC
> > microcontroller that takes snapshots of a free-running decimal counter
> > driven by a 10 MHz timebase (OCXO or GPSDO).
> >
> > The advantage of the timestamp method is that you don't ever miss
> samples,
> > you can time every cycle (if you want), or throw away all but one sample
> > per second or per 10 seconds or per minute, etc. And best of all,
> > timestamping avoids the hassles of the coincidence zone.
> >
> > 5) CPU. A plain microcontroller, or Arduino, or R-Pi can be used. Or if
> > you're on Windows and have a native or USB serial port try this simple
> tool
> > as a demo:
> >
> > http://leapsecond.com/tools/pctsc.exe
> > http://leapsecond.com/tools/pctsc.c
> >
> > 6) An assortment of mains links:
> >
> > http://leapsecond.com/pages/mains/
> > http://leapsecond.com/pages/mains-cv/
> > http://wwwhome.cs.utwente.nl/~ptdeboer/misc/mains.html
> > http://leapsecond.com/pages/mains/mains-adev-mdev-gnuplot-g4.png
> > http://leapsecond.com/pages/tec/mains-clock-ani.gif
> > http://leapsecond.com/pages/ac-detect/
> > http://leapsecond.com/pic/picpet.htm
> > http://leapsecond.com/pic/pp06.htm
> >
> > 7) Final comments.
> >
> > It is tempting to worry about the design, as they are so many out there
> on
> > the web. Which is best? What are the pitfalls? What about noise immunity?
> > What about precision and accuracy? My recommendation is not to over-think
> > this. Just throw something together and see what you've got. Most of the
> > work is with handling the data you get, doing the math, making plots,
> etc.
> > If after the first day you see odd-looking 16 ms jumps in your data then
> > you know you need to pay more attention to trigger level or noise issues.
> >
> > 8) A sound idea.
> >
> > We need someone to try out the sound card method. Send the isolated low
> > voltage AC into the L channel 

Re: [time-nuts] Recommendations for Mains Power Monitor / Logger

[Attila Kinali]

Hi,

I'd like to add two things:

On Sat, 10 Mar 2018 20:46:16 -0800
"Tom Van Baak"  wrote:

> 1) Safety. I usually use a low voltage step-down transformer. This gives 
> isolation and safety. Anything from 3 VAC to 24 VAC is fine.

Please, do not just add a transformer. Make it also impossible to touch
any wire comming from mains or anything that could potentially have
mains voltage on it. In europe, the minimum isolation distance between mains 
and anything on the low voltage side is at least 5mm (IIRC). I recommend
to use at least this much distance in your designs as well, even if a much
smaller distance would be enough to prevent arcing in most cases (the reason
for this large gap is to ensure that dust and humidity do not cause an
isolation fault under normal, household conditions).

 
> 2) Trigger. There are dozens of schematics on the web for capturing the zero-
> crossing of a low-voltage sine wave. You can easily go overboard on this. Or 
> just keep it simple and feed the signal through a resistor directly into a 
> microprocessor input. The internal clamping diodes do their thing. A Schmitt 
> trigger input is helpful but not necessary depending on how your software 
> makes the measurement.

Please do not use the internal clamping diodes of an IC as the main way
to clamp a voltage. These diodes are ment for protection against ESD events.
They are not designed to constantly dissipate energy. If you do it anyways,
the diodes will fail after a while... and slowly at that.
If you need to clamp voltage use two Schottky diodes (BAT54, MBR0502,...)
to Vcc and GND. Also ensure that the current drawn from Vcc at all times
exceedes the current injected into Vcc through the clamping diodes, otherwise
you will have an uncontrolled raise in power supply voltage and might exceed
the rating of your circuit.

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
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Re: [time-nuts] Recommendations for Mains Power Monitor / Logger

[Ryan Stoner]

I used to have one of the FNET units to help them with data and to keep
track of things myself during a period of low voltage in the summer months.
The lowest voltage I saw was about 70 volts. Months of contacting ComEd
directly with the excellent data provided by the unit accomplished nothing.
An email to the Citizens Utility Board with the same data brought an army
of ComEd people to the alley. They confirmed the low voltage and scheduled
a new transformer install. I never got to see the results. My wife and I
moved into our first house. Which loses power in high winds.

The FNET unit I had eventually got killed by the wonky low voltage electric
service. It was a nice piece if equipment that spit out a lot of neat data.
I was super bummed when I sent it back.

--
Ryan Stoner

On Mar 10, 2018 9:31 PM, "Jeremy Nichols"  wrote:

 One possibility is to get an FNET/GridEye unit of the University of
Tennessee's monitoring stations.

Operated by the Power Information Technology Laboratory
 at the University of Tennessee ,
FNET/GridEye is a low-cost, quickly deployable GPS-synchronized wide-area
frequency measurement network. High dynamic accuracy Frequency Disturbance
Recorders (FDRs) are used to measure the frequency, phase angle, and
voltage of the power system at ordinary 120 V outlets. The measurement data
are continuously transmitted via the Internet to the FNET/GridEye servers
hosted at the University of Tennessee and Virginia Tech .


I have Unit 853 of the Western Interconnection in the tabular display in
their web site (http://fnetpublic.utk.edu/tabledisplay.html). The unit,
about the size of a book, connects to the Internet via a cable to my router
and has a power line connection and a small GPS antenna. The LCD display
shows voltage and frequency; unfortunately there's no way to record this
information on site (at home or wherever).

Jeremy
N6WFO

On Sat, Mar 10, 2018 at 2:53 PM, Patrick Murphy  wrote:

> All this talk of varying mains power frequency aberrations has me
> curious what is happening in my own back yard here in Tulsa in the
> USA. Can some recommend a reasonable "introductory level" solution for
> this? (As a fledgling Time-Nut, those two words were hard to say.)
> At the least I would like to watch voltage and frequency, with a
> configurable monitoring and logging interval. I can provide precise
> timing as needed for synchronization and time-stamping. Expanded
> ability to also monitor amperage, various power factors, etc is a plus
> but not required at this point.
>
> I've done some Googling and have found any number of designs. What I
> can't tell is how well they work. I am pretty handy with my hands and
> do not at all mind a DIY solution.
>
> So what do the Oracles say?
>
> Thanks!
>
> -Pat
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Re: [time-nuts] Recommendations for Mains Power Monitor / Logger

[Magnus Danielson]

Hi,

On 03/11/2018 12:53 PM, Bob kb8tq wrote:
> Hi
> 
> So, how good is “good enough?”. My first attempt ran a counter with a 1 us 
> period resolution. 
> (remember, it was tube based …). That turned out to be major overkill in 
> terms of line frequency
> measurement. 60.123 Hz is doing pretty well in terms of line frequency. Even 
> to get that level, you 
> will be doing a bit of filtering (or you are  just watching the last two 
> digits pop around randomly). 
> 
> Your typical time base in a PC is good to a few hundred ppm. That’s giving 
> you an error in the 
> fourth digit of your measurement. With a bit of luck, your sound card 
> timebase may be 5X 
> more accurate than your system clock. (or it may be worse …) it depends a bit 
> on how fancy
> your audio setup is. 
> 
> Adding NTP to your PC will correct for any long term errors. In a rational 
> environment it should 
> get you into the “few ppm” range short term and zero error long term. 
> 
> A GPS gizmo will get you into the parts per billion (or better) range. It 
> might be 100’s of ppb, but it’s
> still *way* better than your CPU clock. The usual auction sites have lots of 
> candidates in the sub $50
> range.There are also places that are happy to sell you shields with GPS 
> devices on them.
> 
> A fancier yet solution is a GPSDO. We are well into overkill at this point. 
> The advantage to using
> one is that it may be the time / frequency standard for your entire lab 
> setup. You are up in the 
> $100 to $500 range for most of them. They will get you into 10’s or 100’s of 
> parts per trillion. 
> 
> There are indeed *lots* of different time sources you could use. The number 
> of alternatives is 
> *much* larger than what’s on the list above.

It so depends on what you do.

Power-grid folks uses phasor-measurement units, following the IEEE
C37.118.1 and .2 spec. In that you sample the V and/or I of the phases
at high rate, downconvert it with a specified filter to whatever
report-rate is requested, frequency shift it with a reference 50 Hz or
60 Hz and then timestamp measurements. For 60 Hz systems, reportrate of
30 samples per second is fairly common, but both 60 and 120 samples per
second is in use. To meet the 0,1 % Total Vector Error, the timing needs
to be within 22 us, but measurement noise can be well below 1 us,
reaching for 100 ns.

The post-processing of the PMU crunches out phase, frequency and
Rate-Of-Change-Of-Frequency. The ROCOF is what we time-nuts call linear
frequency drift.
The remote post-processing can find islanding, inter-area oscillations,
forces oscillations beyond the clear evidence of over and under
production of power. You can see when the network shakes for a larger
even when a whole section of a network oscillates between overpowered
and underpowered before the ringing dies out.

Care must be taken to use data that is remote and local to get good
observability of mode. This also depends on wither you measure voltage
or current, and voltage will only have observability on the ends where
as current will have observability in the middle, just as you expect
from a half-wave bipole antenna.

For phase measures, you want to compare two measures to see the phase
difference between two points. It is interesting to see two sources
struggle to balance and how that changes with power consumption, power
production and strength of the interconnected network.

Find out more here:
https://rubidium.dyndns.org/~magnus/papers/KTH_paper1.pdf

In general, NASPI has a wide range of publications online that may be of
good reference. They formmed the Time Synchronization Task Force as a
result of me informing them about the 26 Jan 2016 incident, and their
report could be useful for many:
https://www.naspi.org/node/608

Cheers,
Magnus

> 
> Bob
> 
>> On Mar 10, 2018, at 11:46 PM, Tom Van Baak  wrote:
>>
>>> I've done some Googling and have found any number of designs.
>>
>> Pat,
>>
>> 1) Safety. I usually use a low voltage step-down transformer. This gives 
>> isolation and safety. Anything from 3 VAC to 24 VAC is fine.
>>
>> 2) Trigger. There are dozens of schematics on the web for capturing the 
>> zero-crossing of a low-voltage sine wave. You can easily go overboard on 
>> this. Or just keep it simple and feed the signal through a resistor directly 
>> into a microprocessor input. The internal clamping diodes do their thing. A 
>> Schmitt trigger input is helpful but not necessary depending on how your 
>> software makes the measurement.
>>
>> 3) Timebase. Given the long-term accuracy of mains (seconds a day, seconds a 
>> year) you don't need an atomic timebase. If you collect data for a couple of 
>> days any old XO will be fine. If you plan to collect data for months you may 
>> want a OCXO. Most of us just use cheap GPS receivers.
>>
>> 4) Measurement. There are many ways to measure the signal. You can measure 
>> frequency directly, as with a frequency counter. You get nice data but it 
>> may 

Re: [time-nuts] Recommendations for Mains Power Monitor / Logger

[Didier Juges]

I like the sound card idea. However I believe it's much better to use the
two channels. At least under Windows, it is much easier to track the
relative phase of the two channels of one sound card than the absolute
phase of one channel compared to the system clock.
I have written an audio VNA in Visual Basic that has all the building
blocks.
Unfortunately, it is harder and harder to develop VB 6.0 under Windows 10
so I am not doing much of that anymore.
Since I am doing it using FFT, filtering (and harmonics measurements) come
for free.

On Mar 10, 2018 10:47 PM, "Tom Van Baak"  wrote:

> > I've done some Googling and have found any number of designs.
>
> Pat,
>
> 1) Safety. I usually use a low voltage step-down transformer. This gives
> isolation and safety. Anything from 3 VAC to 24 VAC is fine.
>
> 2) Trigger. There are dozens of schematics on the web for capturing the
> zero-crossing of a low-voltage sine wave. You can easily go overboard on
> this. Or just keep it simple and feed the signal through a resistor
> directly into a microprocessor input. The internal clamping diodes do their
> thing. A Schmitt trigger input is helpful but not necessary depending on
> how your software makes the measurement.
>
> 3) Timebase. Given the long-term accuracy of mains (seconds a day, seconds
> a year) you don't need an atomic timebase. If you collect data for a couple
> of days any old XO will be fine. If you plan to collect data for months you
> may want a OCXO. Most of us just use cheap GPS receivers.
>
> 4) Measurement. There are many ways to measure the signal. You can measure
> frequency directly, as with a frequency counter. You get nice data but it
> may not be perfect long-term due to dead time or gating effects in the
> counter.
>
> So what most of us do is measure phase (time error) instead. One way is to
> make time interval measurements from a given mains cycle to a GPS 1PPS tick
> or vice versa, from each GPS/1PPS tick to the very next mains cycle. Either
> way you get about sample per second. If you're in search of perfection it
> gets a bit tricky when the two signals are in a coincidence zone.
>
> The other approach is not to use a frequency or time interval counter at
> all. Instead you timestamp each cycle, or every 60th cycle. Unix-like
> systems have this capability. See Hal's posting. I use a picPET, a PIC
> microcontroller that takes snapshots of a free-running decimal counter
> driven by a 10 MHz timebase (OCXO or GPSDO).
>
> The advantage of the timestamp method is that you don't ever miss samples,
> you can time every cycle (if you want), or throw away all but one sample
> per second or per 10 seconds or per minute, etc. And best of all,
> timestamping avoids the hassles of the coincidence zone.
>
> 5) CPU. A plain microcontroller, or Arduino, or R-Pi can be used. Or if
> you're on Windows and have a native or USB serial port try this simple tool
> as a demo:
>
> http://leapsecond.com/tools/pctsc.exe
> http://leapsecond.com/tools/pctsc.c
>
> 6) An assortment of mains links:
>
> http://leapsecond.com/pages/mains/
> http://leapsecond.com/pages/mains-cv/
> http://wwwhome.cs.utwente.nl/~ptdeboer/misc/mains.html
> http://leapsecond.com/pages/mains/mains-adev-mdev-gnuplot-g4.png
> http://leapsecond.com/pages/tec/mains-clock-ani.gif
> http://leapsecond.com/pages/ac-detect/
> http://leapsecond.com/pic/picpet.htm
> http://leapsecond.com/pic/pp06.htm
>
> 7) Final comments.
>
> It is tempting to worry about the design, as they are so many out there on
> the web. Which is best? What are the pitfalls? What about noise immunity?
> What about precision and accuracy? My recommendation is not to over-think
> this. Just throw something together and see what you've got. Most of the
> work is with handling the data you get, doing the math, making plots, etc.
> If after the first day you see odd-looking 16 ms jumps in your data then
> you know you need to pay more attention to trigger level or noise issues.
>
> 8) A sound idea.
>
> We need someone to try out the sound card method. Send the isolated low
> voltage AC into the L channel and a GPS 1PPS into the R channel. "The rest
> is just software." Note that because you have access to the entire sine
> wave there's a lot you can do with this method besides making charts of
> time drift or frequency deviation from the zero-crossings.
>
> For an even cheaper solution, forget the GPS receiver and the R channel --
> since the PC (if running NTP) already knows the correct time. And skip the
> AC transformer too -- instead just hang a foot of wire off the L channel
> input. There's mains hum everywhere. It would be the one time in your life
> where the ever-present audio hum actually has a good use.
>
> /tvb
>
> - Original Message -
> From: "Patrick Murphy" 
> To: 
> Sent: Saturday, March 10, 2018 2:53 PM
> Subject: [time-nuts] Recommendations for Mains Power Monitor / Logger
>
>
> All this 

Re: [time-nuts] Recommendations for Mains Power Monitor / Logger

[ewkehren via time-nuts]

My 20 year old Junghans`s had no problemBert Kehren Palm City Florida


Sent from my Galaxy Tab® A
 Original message From: Tom Van Baak  
Date: 3/11/18  8:32 AM  (GMT-05:00) To: Discussion of precise time and 
frequency measurement  Subject: Re: [time-nuts] 
Recommendations for Mains Power Monitor / Logger 
Bob,

Correct, measuring mains frequency to a couple of digits is not hard. What 
makes an interesting challenge is to monitor mains, "kitchen clock", phase 
drift. And to do it with cycle accuracy; no slips. Note that to measure down to 
1 cycle over 1 day is 0.2 ppm. Over a month, 6 ppb, and over a year, 5e-10. So 
the numbers add up and you see why we use atomic standards or GPS or even NTP 
as a long-term reference for this.

Your measurement system needs to have short- and long-term stability ~10x 
better than:
    http://leapsecond.com/pic/mains-adev-mdev-gnuplot-g4.png

Again, that's not asking a lot. But it makes a really fun project. Much of what 
you ever need to know about time & frequency metrology can be done by a student 
with $10 in parts and a 60 Hz outlet.

/tvb

p.s. Yes, it's very early here on the west coast, but I had to check how badly 
my WWVB clocks handled DST a few hours ago.

- Original Message - 
From: "Bob kb8tq" 
To: "Discussion of precise time and frequency measurement" 
Sent: Sunday, March 11, 2018 4:53 AM
Subject: Re: [time-nuts] Recommendations for Mains Power Monitor / Logger


Hi

So, how good is “good enough?”. My first attempt ran a counter with a 1 us 
period resolution. 
(remember, it was tube based …). That turned out to be major overkill in terms 
of line frequency
measurement. 60.123 Hz is doing pretty well in terms of line frequency. Even to 
get that level, you 
will be doing a bit of filtering (or you are  just watching the last two digits 
pop around randomly). 

Your typical time base in a PC is good to a few hundred ppm. That’s giving you 
an error in the 
fourth digit of your measurement. With a bit of luck, your sound card timebase 
may be 5X 
more accurate than your system clock. (or it may be worse …) it depends a bit 
on how fancy
your audio setup is. 

Adding NTP to your PC will correct for any long term errors. In a rational 
environment it should 
get you into the “few ppm” range short term and zero error long term. 

A GPS gizmo will get you into the parts per billion (or better) range. It might 
be 100’s of ppb, but it’s
still *way* better than your CPU clock. The usual auction sites have lots of 
candidates in the sub $50
range.There are also places that are happy to sell you shields with GPS devices 
on them.

A fancier yet solution is a GPSDO. We are well into overkill at this point. The 
advantage to using
one is that it may be the time / frequency standard for your entire lab setup. 
You are up in the 
$100 to $500 range for most of them. They will get you into 10’s or 100’s of 
parts per trillion. 

There are indeed *lots* of different time sources you could use. The number of 
alternatives is 
*much* larger than what’s on the list above.

Bob

> On Mar 10, 2018, at 11:46 PM, Tom Van Baak  wrote:
> 
>> I've done some Googling and have found any number of designs.
> 
> Pat,
> 
> 1) Safety. I usually use a low voltage step-down transformer. This gives 
> isolation and safety. Anything from 3 VAC to 24 VAC is fine.
> 
> 2) Trigger. There are dozens of schematics on the web for capturing the 
> zero-crossing of a low-voltage sine wave. You can easily go overboard on 
> this. Or just keep it simple and feed the signal through a resistor directly 
> into a microprocessor input. The internal clamping diodes do their thing. A 
> Schmitt trigger input is helpful but not necessary depending on how your 
> software makes the measurement.
> 
> 3) Timebase. Given the long-term accuracy of mains (seconds a day, seconds a 
> year) you don't need an atomic timebase. If you collect data for a couple of 
> days any old XO will be fine. If you plan to collect data for months you may 
> want a OCXO. Most of us just use cheap GPS receivers.
> 
> 4) Measurement. There are many ways to measure the signal. You can measure 
> frequency directly, as with a frequency counter. You get nice data but it may 
> not be perfect long-term due to dead time or gating effects in the counter.
> 
> So what most of us do is measure phase (time error) instead. One way is to 
> make time interval measurements from a given mains cycle to a GPS 1PPS tick 
> or vice versa, from each GPS/1PPS tick to the very next mains cycle. Either 
> way you get about sample per second. If you're in search of perfection it 
> gets a bit tricky when the two signals are in a coincidence zone.
> 
> The other approach is not to use a frequency or time interval counter at all. 
> Instead you timestamp each cycle, or every 60th cycle. Unix-like systems have 
> this capability. See 

Re: [time-nuts] Recommendations for Mains Power Monitor / Logger

[Bob kb8tq]

Hi

“Back in the day” we used WWV and the kitchen clock for that sort of thing……

Bob

> On Mar 11, 2018, at 8:32 AM, Tom Van Baak  wrote:
> 
> Bob,
> 
> Correct, measuring mains frequency to a couple of digits is not hard. What 
> makes an interesting challenge is to monitor mains, "kitchen clock", phase 
> drift. And to do it with cycle accuracy; no slips. Note that to measure down 
> to 1 cycle over 1 day is 0.2 ppm. Over a month, 6 ppb, and over a year, 
> 5e-10. So the numbers add up and you see why we use atomic standards or GPS 
> or even NTP as a long-term reference for this.
> 
> Your measurement system needs to have short- and long-term stability ~10x 
> better than:
>http://leapsecond.com/pic/mains-adev-mdev-gnuplot-g4.png
> 
> Again, that's not asking a lot. But it makes a really fun project. Much of 
> what you ever need to know about time & frequency metrology can be done by a 
> student with $10 in parts and a 60 Hz outlet.
> 
> /tvb
> 
> p.s. Yes, it's very early here on the west coast, but I had to check how 
> badly my WWVB clocks handled DST a few hours ago.
> 
> - Original Message - 
> From: "Bob kb8tq" 
> To: "Discussion of precise time and frequency measurement" 
> 
> Sent: Sunday, March 11, 2018 4:53 AM
> Subject: Re: [time-nuts] Recommendations for Mains Power Monitor / Logger
> 
> 
> Hi
> 
> So, how good is “good enough?”. My first attempt ran a counter with a 1 us 
> period resolution. 
> (remember, it was tube based …). That turned out to be major overkill in 
> terms of line frequency
> measurement. 60.123 Hz is doing pretty well in terms of line frequency. Even 
> to get that level, you 
> will be doing a bit of filtering (or you are  just watching the last two 
> digits pop around randomly). 
> 
> Your typical time base in a PC is good to a few hundred ppm. That’s giving 
> you an error in the 
> fourth digit of your measurement. With a bit of luck, your sound card 
> timebase may be 5X 
> more accurate than your system clock. (or it may be worse …) it depends a bit 
> on how fancy
> your audio setup is. 
> 
> Adding NTP to your PC will correct for any long term errors. In a rational 
> environment it should 
> get you into the “few ppm” range short term and zero error long term. 
> 
> A GPS gizmo will get you into the parts per billion (or better) range. It 
> might be 100’s of ppb, but it’s
> still *way* better than your CPU clock. The usual auction sites have lots of 
> candidates in the sub $50
> range.There are also places that are happy to sell you shields with GPS 
> devices on them.
> 
> A fancier yet solution is a GPSDO. We are well into overkill at this point. 
> The advantage to using
> one is that it may be the time / frequency standard for your entire lab 
> setup. You are up in the 
> $100 to $500 range for most of them. They will get you into 10’s or 100’s of 
> parts per trillion. 
> 
> There are indeed *lots* of different time sources you could use. The number 
> of alternatives is 
> *much* larger than what’s on the list above.
> 
> Bob
> 
>> On Mar 10, 2018, at 11:46 PM, Tom Van Baak  wrote:
>> 
>>> I've done some Googling and have found any number of designs.
>> 
>> Pat,
>> 
>> 1) Safety. I usually use a low voltage step-down transformer. This gives 
>> isolation and safety. Anything from 3 VAC to 24 VAC is fine.
>> 
>> 2) Trigger. There are dozens of schematics on the web for capturing the 
>> zero-crossing of a low-voltage sine wave. You can easily go overboard on 
>> this. Or just keep it simple and feed the signal through a resistor directly 
>> into a microprocessor input. The internal clamping diodes do their thing. A 
>> Schmitt trigger input is helpful but not necessary depending on how your 
>> software makes the measurement.
>> 
>> 3) Timebase. Given the long-term accuracy of mains (seconds a day, seconds a 
>> year) you don't need an atomic timebase. If you collect data for a couple of 
>> days any old XO will be fine. If you plan to collect data for months you may 
>> want a OCXO. Most of us just use cheap GPS receivers.
>> 
>> 4) Measurement. There are many ways to measure the signal. You can measure 
>> frequency directly, as with a frequency counter. You get nice data but it 
>> may not be perfect long-term due to dead time or gating effects in the 
>> counter.
>> 
>> So what most of us do is measure phase (time error) instead. One way is to 
>> make time interval measurements from a given mains cycle to a GPS 1PPS tick 
>> or vice versa, from each GPS/1PPS tick to the very next mains cycle. Either 
>> way you get about sample per second. If you're in search of perfection it 
>> gets a bit tricky when the two signals are in a coincidence zone.
>> 
>> The other approach is not to use a frequency or time interval counter at 
>> all. Instead you timestamp each cycle, or every 60th cycle. Unix-like 
>> systems have this capability. See Hal's posting. I use a 

Re: [time-nuts] Recommendations for Mains Power Monitor / Logger

[Bob kb8tq]

Hi

So, how good is “good enough?”. My first attempt ran a counter with a 1 us 
period resolution. 
(remember, it was tube based …). That turned out to be major overkill in terms 
of line frequency
measurement. 60.123 Hz is doing pretty well in terms of line frequency. Even to 
get that level, you 
will be doing a bit of filtering (or you are  just watching the last two digits 
pop around randomly). 

Your typical time base in a PC is good to a few hundred ppm. That’s giving you 
an error in the 
fourth digit of your measurement. With a bit of luck, your sound card timebase 
may be 5X 
more accurate than your system clock. (or it may be worse …) it depends a bit 
on how fancy
your audio setup is. 

Adding NTP to your PC will correct for any long term errors. In a rational 
environment it should 
get you into the “few ppm” range short term and zero error long term. 

A GPS gizmo will get you into the parts per billion (or better) range. It might 
be 100’s of ppb, but it’s
still *way* better than your CPU clock. The usual auction sites have lots of 
candidates in the sub $50
range.There are also places that are happy to sell you shields with GPS devices 
on them.

A fancier yet solution is a GPSDO. We are well into overkill at this point. The 
advantage to using
one is that it may be the time / frequency standard for your entire lab setup. 
You are up in the 
$100 to $500 range for most of them. They will get you into 10’s or 100’s of 
parts per trillion. 

There are indeed *lots* of different time sources you could use. The number of 
alternatives is 
*much* larger than what’s on the list above.

Bob

> On Mar 10, 2018, at 11:46 PM, Tom Van Baak  wrote:
> 
>> I've done some Googling and have found any number of designs.
> 
> Pat,
> 
> 1) Safety. I usually use a low voltage step-down transformer. This gives 
> isolation and safety. Anything from 3 VAC to 24 VAC is fine.
> 
> 2) Trigger. There are dozens of schematics on the web for capturing the 
> zero-crossing of a low-voltage sine wave. You can easily go overboard on 
> this. Or just keep it simple and feed the signal through a resistor directly 
> into a microprocessor input. The internal clamping diodes do their thing. A 
> Schmitt trigger input is helpful but not necessary depending on how your 
> software makes the measurement.
> 
> 3) Timebase. Given the long-term accuracy of mains (seconds a day, seconds a 
> year) you don't need an atomic timebase. If you collect data for a couple of 
> days any old XO will be fine. If you plan to collect data for months you may 
> want a OCXO. Most of us just use cheap GPS receivers.
> 
> 4) Measurement. There are many ways to measure the signal. You can measure 
> frequency directly, as with a frequency counter. You get nice data but it may 
> not be perfect long-term due to dead time or gating effects in the counter.
> 
> So what most of us do is measure phase (time error) instead. One way is to 
> make time interval measurements from a given mains cycle to a GPS 1PPS tick 
> or vice versa, from each GPS/1PPS tick to the very next mains cycle. Either 
> way you get about sample per second. If you're in search of perfection it 
> gets a bit tricky when the two signals are in a coincidence zone.
> 
> The other approach is not to use a frequency or time interval counter at all. 
> Instead you timestamp each cycle, or every 60th cycle. Unix-like systems have 
> this capability. See Hal's posting. I use a picPET, a PIC microcontroller 
> that takes snapshots of a free-running decimal counter driven by a 10 MHz 
> timebase (OCXO or GPSDO).
> 
> The advantage of the timestamp method is that you don't ever miss samples, 
> you can time every cycle (if you want), or throw away all but one sample per 
> second or per 10 seconds or per minute, etc. And best of all, timestamping 
> avoids the hassles of the coincidence zone.
> 
> 5) CPU. A plain microcontroller, or Arduino, or R-Pi can be used. Or if 
> you're on Windows and have a native or USB serial port try this simple tool 
> as a demo:
> 
>http://leapsecond.com/tools/pctsc.exe
>http://leapsecond.com/tools/pctsc.c
> 
> 6) An assortment of mains links:
> 
> http://leapsecond.com/pages/mains/
> http://leapsecond.com/pages/mains-cv/
> http://wwwhome.cs.utwente.nl/~ptdeboer/misc/mains.html
> http://leapsecond.com/pages/mains/mains-adev-mdev-gnuplot-g4.png
> http://leapsecond.com/pages/tec/mains-clock-ani.gif
> http://leapsecond.com/pages/ac-detect/
> http://leapsecond.com/pic/picpet.htm
> http://leapsecond.com/pic/pp06.htm
> 
> 7) Final comments.
> 
> It is tempting to worry about the design, as they are so many out there on 
> the web. Which is best? What are the pitfalls? What about noise immunity? 
> What about precision and accuracy? My recommendation is not to over-think 
> this. Just throw something together and see what you've got. Most of the work 
> is with handling the data you get, doing the math, making plots, etc. If 
> after the 

Re: [time-nuts] Recommendations for Mains Power Monitor / Logger

[Bill Hawkins]

Well, this synchronization follows the laws of physics. If the energy
generated doesn't equal the energy consumed, then the frequency may
raise or lower. This is for steam turbines. If the energy come front an
inverter from a DC tie line, as it does from the four regions in the US,
the frequency is anything it wants to be. Well not quite. Raising the
inverter frequency a hair causes the tie line to be the major source of
energy. One could track the use of energy by frequency to make
investment decisions in manufacturer's stocks.

The problem with zero crossing triggers is the amount of noise caused by
solid state power supplies and by tap changing by the power companies to
match loads to minimize transmission losses. I've considered using a
mechanical synchronous motor and slotted wheel to eliminate noise near
the zero crossing, but now that I am 80, I don't give a darn, you see.

Bill Hawkins


 -Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob
Albert via time-nuts
Sent: Saturday, March 10, 2018 5:58 PM

 There isn't a whole lot of justification for measuring power line
frequency.  We are all synchronized (in the first world at least) and
while there are phase instabilities, it's seldom the frequency varies
enough to overcome the noise.
As for voltage, it's much more steady than several years ago.  Most
people have 122 Volts, give or take a couple.  Again, not a whole lot of
purpose in recording it.
The distortion is another story.  It's never quite sinusoidal but there
is also some random noise picked up between the generators and the
load.  Looking at the 'scope it's seldom it looks like the textbook
picture of a sine wave.  Chances are most distortion is odd harmonic.
Distortion probably mostly comes from loads which are not resistive,
such as switching power supplies, rectifiers, fluorescent lamps, and
such.  These loads draw currents that are not sinusoids and so cause
voltage drops that are also of that character.
Bob

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