ise time and frequency measurement
> Subject: Re: [time-nuts] Thunderbolt? (re simple gpsdo.) >> capacitors
>
> In message
>
> , Azelio Boriani writes:
>
> >I have googled extensively trying to find something about the dual
> >capacitor method of reducing the
Sent: Thursday, January 05, 2012 5:50 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Thunderbolt? (re simple gpsdo.) >> capacitors
In message
, Azelio Boriani writes:
>I have googled extensively trying to find something about the dual
>capacitor m
easurement
Subject: Re: [time-nuts] Thunderbolt? (re simple gpsdo.) >> capacitors
In message
, Azelio Boriani writes:
>I have googled extensively trying to find something about the dual
>capacitor method of reducing the leakage current... nothing found. Please,
>can you indicate
Anyone contemplating building an analog loop for a GPSDO should
consider that it can be very tricky and expensive to attain great
performance. That's why the commercial ones are primarily digital -
it puts the most severe performance requirements in the least amount
of analog circuitry - the DA
Thanks. Me too: now I got it, sort of bootstrap and now I see that R2 is
needed because the real filter is R2*C2 and the leakage is not totally
compensated if C1 has to move to a new value -> R*C1 wrote:
> Poul
> Thanks have been kind of following this thread and the diagram did not make
> a lot o
Poul
Thanks have been kind of following this thread and the diagram did not make
a lot of sense.
I figured I missed part of the thread. But this clears it up nicely.
Regards
Paul.
WB8TSL
On Thu, Jan 5, 2012 at 5:49 PM, Poul-Henning Kamp wrote:
> In message g...@mail.gmail.com>
> , Azelio Boriani
In message
, Azelio Boriani writes:
>I have googled extensively trying to find something about the dual
>capacitor method of reducing the leakage current... nothing found. Please,
>can you indicate anything for me to learn more?
It is very simple:
R1 charges C1 to the DC potential and therefor
... don't know but judging from the very simple ASCII schematic I'll say no
because the lower capacitor is grounded. There is some sort of feedback I
can't figure out, too simple that schematic.
On Thu, Jan 5, 2012 at 11:27 PM, wrote:
> Perhaps the dual cap is a differential implementation of th
Perhaps the dual cap is a differential implementation of the filter/integrator.
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rs when a 10 %
> leakage would be tolerable.
> I tested a 10,000 sec TC filter using a 10 meg and 1000 uF, and got under
> 1% leakage error open loop.
>
> ws
>
>
> *******
>
> [time-nuts] Thunderbolt? (re simple gpsdo.) >> capacitors
> Poul-Hennin
closed loop filters when a 10 %
leakage would be tolerable.
I tested a 10,000 sec TC filter using a 10 meg and 1000 uF, and got under 1%
leakage error open loop.
ws
***
[time-nuts] Thunderbolt? (re simple gpsdo.) >> capacitors
Poul-Henning Kamp phk at phk.freebsd.dk
The l
On Fri, 30 Dec 2011 22:54:26 -0800
Chris Albertson wrote:
> I don't count anything with a computer and software inside as
> "simple". My definition of a simple device is a capacitor or a
> transistor or I guess a single flip-flop or op-amp. A simple
> controller would some how use about two d
In message <80B26DC756AA45DD84E4EB9E14B58998@Warcon28Gz>, "WarrenS" writes:
>The leakage current noise I measured was way below insignificant when things
>are properly scaled.
Really stupid question: Couldn't the "double condensor" from voltage
references trick be used to eliminate the leakage
ure
which did changed it's capacitance and leakage, but had no effect on it's
charge voltage.
I guess the charge is not Fixed, so not the same thing as changing the value
by paralleling the cap.
ws
**
[time-nuts] Thunderbolt? (re simple gpsdo.) >> capacitors
Bo
lf Of Chris Albertson
Sent: Tuesday, January 03, 2012 12:35 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Thunderbolt? (re simple gpsdo.) >> capacitors
On Tue, Jan 3, 2012 at 9:14 AM, Bob Camp wrote:
> Hi
>
> Using electrolytic caps in timing a
On Tue, Jan 3, 2012 at 9:14 AM, Bob Camp wrote:
> Hi
>
> Using electrolytic caps in timing applications is a bit exciting. Their
> leakage current changes each time you change the voltage on them. It's
> enough of a change to significantly impact long time constants. In some
> cases the capacitan
iscussion of precise time and frequency measurement
Subject: Re: [time-nuts] Thunderbolt? (re simple gpsdo.)
> Time constant is just R*C. If you have a 1000uF cap and a 1K resistor you
> have 1 second. In theory you could build 100s just by using a 100K
resistor
> but I think real wor
Hal wrote:
Does anybody know anything about the temperature coefficients of large caps?
I'm not interested in the frequency shift of the filter as the temperature
but the voltage shift due to a fixed charge as the capacitance changes.
The common rule of thumb is "thousands of ppm per
degree
>> For those who aren't familiar with this trick, it's easy to make a low
>> pass filter in software:
>> X = X*(1-k) + k*new
> Designing filters seems like an art. What is the frequency response of the
> above for different values of k? I tend to like FIR filters because I think
> I understand
On Mon, 02 Jan 2012 17:14:37 -0800, Hal Murray
wrote:
>
>> Time constant is just R*C. If you have a 1000uF cap and a 1K resistor you
>> have 1 second. In theory you could build 100s just by using a 100K resistor
>> but I think real world components are not perfect enough.
>
>Does anybody know
> Time constant is just R*C. If you have a 1000uF cap and a 1K resistor you
> have 1 second. In theory you could build 100s just by using a 100K resistor
> but I think real world components are not perfect enough.
Does anybody know anything about the temperature coefficients of large caps?
I
My FE-5680A and Thunderbolt have been well behaved for the
last 16 hours. The Thunderbolt is using 3.00 FW and had its
feedback settings optimized by Lady Heather. AMU mask is 7.0.
No adjustments were made to the Rb during this run.
--
Chuck Forsberg WA7KGX N2469R c...@omen.com www.omen.
Here is another analog control example based on the quick and dirty example
below.
It is a simple and Very poor GPSDO Rb design as far as noise jitter goes
because of the nonlinear and high Phase detector gain, and high 1e-8 noise
jitter on the PPS,
but still no problem to do with cheap bas
Hi
If you do a quick Google search for "insulation resistance" you get to:
http://www.electrocube.com/support/insulation_resistance.asp
or a bunch of similar information. The capacitor it's self (no external
resistance at all) has a time constant between it's capacitance and internal
leakage.
Kasper,
I like your style! Small ROM = no inessential features! I shall be
studying this code, getting capture working with no capture hardware
is a real pain.
On 2 January 2012 00:53, Kasper Pedersen wrote:
> On 01/01/2012 12:23 PM, Tom Harris wrote:
>
>> I too have been mulling over a minimal
Hi
The answer is (as always) "no free lunch". An op amp simulating a capacitor is
always going to be performance limited. Different limitations come in with
different circuits, but they all suffer from noise / drift / leakage. Put
another way - for a long time constant, you are just as good off
Hi
For some designs (like a Rb) the time constant may be in the "days" range….
Even for something simple, you can easily get out to several thousand seconds.
You also need low noise past the cutoff time (for short times the cap may help
you). That's going to get you into resistor noise and / o
Gyrators are usually used to create impractical inductances or
frequency dependant negative resistances but I suppose you could. I
do not think you would gain anything though since you would be trading
one set of non-ideal behaviors for a different set. This is
especially the case since the non-i
ght and compromise, most of these do not
need to apply, therefore they are not an issue even at the highest performance
levels.
ws
***
[time-nuts] Thunderbolt? (re simple gpsdo.)
Hal Murray hmurray at megapathdsl.net
Sun Jan 1 01:56:46 UTC 2012
> As soon as you say "Softwar
http://www.falstad.com/circuit/e-capmult.html
I did not take the time to analyze...
Don
David
> Jim Williams did this in one of his designs for measuring low
> frequency reference noise. The large value low leakage wet tantalum
> capacitor he used was like $400 and it took 24 hours for the
> diel
Aren't there op-amp circuits that create a large capacitance? The gyrator?
Don
David
> Jim Williams did this in one of his designs for measuring low
> frequency reference noise. The large value low leakage wet tantalum
> capacitor he used was like $400 and it took 24 hours for the
> dielectric ab
Jim Williams did this in one of his designs for measuring low
frequency reference noise. The large value low leakage wet tantalum
capacitor he used was like $400 and it took 24 hours for the
dielectric absorption to settle:
http://www.linear.com/docs/28585
You can get the necessary time constant
Hi
Actually a minimalist GPSDO *could* be a person looking at a scope and tweaking
a pot every so often. It all depends on what the desired result is (how
accurate / how automated / how failure resistant). Is simplicity measured by
low cost, low parts count, easy to find parts, or easy to work
Hi
Any real world capacitor will have a dielecric with an associated insulation
resistance. It's a "more money gets better performance" sort of thing, but
there are indeed limits. A 1000 uF cap that has a "good" insulation resistance
number might cost you more than some new cars….
No free lunc
On 01/01/2012 12:23 PM, Tom Harris wrote:
> I too have been mulling over a minimal GPSDO.
>
> Has anyone mentioned a PWM DAC? Even a "toy" microcontroller like the
> Atmel AVRs can generate 16 bit resolution PWM, which sounds like it
..
> So a minimal GPSDO looks like a simple microcontroller (
I too have been mulling over a minimal GPSDO.
Has anyone mentioned a PWM DAC? Even a "toy" microcontroller like the
Atmel AVRs can generate 16 bit resolution PWM, which sounds like it
would be heaps. As long as the voltage reference is low noise, it does
not matter if it drifts slowly, since the c
On Sat, Dec 31, 2011 at 5:56 PM, Hal Murray wrote:
>
> > As soon as you say "Software" the device is no longer simple.Even a
> > microprocessor is a very complex device and so is its development system.
> > The software inside the uP is not simple either if you count the number
> of
> > possi
On Sat, 31 Dec 2011 17:56:46 -0800, Hal Murray
wrote:
>This looks like fun to me, but I like writing that sort of code. Note that
>it doesn't need an OS or even any libraries.
Both designs look fun to me but for different reasons. The analog
design requires attention to leakage and noise whil
> As soon as you say "Software" the device is no longer simple.Even a
> microprocessor is a very complex device and so is its development system.
> The software inside the uP is not simple either if you count the number of
> possible paths through the code (2 raided to the power of the number
t; detector for low freq signals.
> Remove the EFC feedback, Reduce the 100 to 1 divider to two or so and
> you
> can use this to measure and/or manually set a Rb Osc to be on frequency
> if
> you have an accurate 1PPS signal.
>
> ws
>
>
> [time-nuts]
r so and you
can use this to measure and/or manually set a Rb Osc to be on frequency if
you have an accurate 1PPS signal.
ws
********
[time-nuts] Thunderbolt? (re simple gpsdo.)
Chris Albertson albertson.chris at gmail.com
Sat Dec 31 20:34:14 UTC 2011
I think this is the simplest design
I think this is the simplest design that can still work, just one flip
flop, divider and a capacitor.
What level of performance did you get?I think it depends on how big the
integrating capacitor is and how stable the VCXO is. I guess if you
switched to using the t-bolt the performance was n
Chris
Here is a GPSDO I built that better fits Your definition of "Simple". I used
this as my freq standard before getting a TBolt.
1) Feed the PPS output of an oncore GPS timing engine which has 1 Hz or
better yet 100 Hz output to the clk of a D FlipFlop (74HC74)
2) Feed the FF's D from a
In my opinion you have to look at it from the point of application.
Hopefully I will be able to share the test results soon. For us DNL is key, INL
is specked over the full range and since we use it in a filter application,
based on the data that I have, can be ignored.
In a Rb application I
PI controllers can be implemented analog only. For the PPS they need
large capacitors that are the equivalent of averaging (sum and accumulate)
in a software implemented controller.
On Sat, Dec 31, 2011 at 7:54 AM, Chris Albertson
wrote:
> On Fri, Dec 30, 2011 at 11:46 AM, Stanley wrote:
>
On Fri, Dec 30, 2011 at 11:46 AM, Stanley wrote:
>
>
>>
>>> "What is the simplest design for a GPSDO that uses only the PPS signal
>>> from
>>> a modern GPS?"
>>
>>
>> Some sort of oscillator with a voltage control.
>> CPU with a timer/counter that can capture the PPS.
>> DAC.
>> Software.
>>
>
>
On Fri, Dec 30, 2011 at 10:16 AM, Hal Murray wrote:
>
>> "What is the simplest design for a GPSDO that uses only the PPS signal from
>> a modern GPS?"
>
> Some sort of oscillator with a voltage control.
> CPU with a timer/counter that can capture the PPS.
> DAC.
> Software.
As soon as you say "So
Don't need to stretch, use the two hardware interrupt pins...
Don
Chuck Forsberg WA7KGX N2469R
> I was thinking ... starting with a 5680a and a GPS with
> accurate 1pps but no 10 MHz ...
>
> Feed both 1pps signals to a 74ls123 to stretch the pulses to something
> longer.
> A 74ls74 is strobed by o
Did you test the LTC1655 INL? The data sheet says plus or minus 20
counts maximum.
I suspect Linear Technology designed those low DNL high INL parts for
just this sort of application where only monotonic behavior really
matters. Their equivalent current output DAC costs about twice as
much not i
I was thinking ... starting with a 5680a and a GPS with
accurate 1pps but no 10 MHz ...
Feed both 1pps signals to a 74ls123 to stretch the pulses to something
longer.
A 74ls74 is strobed by one of the one-shots, its D input being the other
one-shot.
Connect both one-shots and the 74 to an Ard
: time-nuts-boun...@febo.com
Date: Fri, 30 Dec 2011 17:48:24
To:
Reply-To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Thunderbolt? (re simple gpsdo.)
Over the last two years along with two list members that may want to pipe
in, I have spend a large amount
From: Hal Murray
To: Discussion of precise time and frequency measurement
Sent: Fri, December 30, 2011 5:35:56 PM
Subject: Re: [time-nuts] Thunderbolt? (re simple gpsdo.)
> Yes, the DAC+reference is challenging and one way to go may be the
> coarse+fine approach to avoid large (18bit and beyond) D
No free lunch, of course, but I want to avoid dithering DACs. The 18bit DAC
(AD5680) is a 16bit+dithering, I think to use the AD5660 + AD5241 (already
available) the pot has a tempco of 30ppm/degree and a noise of
14nV/sqr(Hz). Maybe I have to find something better but to make the first
try is avai
Over the last two years along with two list members that may want to pipe
in, I have spend a large amount of time on D/A's and we went as far as
developing a test board using the LTC 2440 and testing numerous D/A's taking in
to consideration performance, solderability, cost, availability and
> Yes, the DAC+reference is challenging and one way to go may be the
> coarse+fine approach to avoid large (18bit and beyond) DAC. My last GPSDO
> has an 18bit DAC but now I'm thinking to try the 8bit digital pot + 16bit
> DAC op-amp combined. The reference can't be overlooked anyway.
Be careful
Yes, the DAC+reference is challenging and one way to go may be the
coarse+fine approach to avoid large (18bit and beyond) DAC. My last GPSDO
has an 18bit DAC but now I'm thinking to try the 8bit digital pot + 16bit
DAC op-amp combined. The reference can't be overlooked anyway.
On Fri, Dec 30, 2011
On 12/30/11 11:39 AM, Robert LaJeunesse wrote:
How about USB to an FT232 that talks SPI to a low-cost DAC or digital pot? Would
need a stable reference, though.
There's a bunch of eval boards from LTC, etc. which use this strategy.
Looks like a serial port to the computer, simple ASCII protoco
The DAC and it's voltage reference looks to be the weak link in the digital
control and the "simple" goal. The CPU I mentioned before on closer look
doesn't have a good DAC. The 20 bit TI DAC1220 looks better but not sure you
can find it in the same package as the CPU. The cheap Rb standards wit
> >Sent: Dec 30, 2011 12:42 PM
> >To: Discussion of precise time and frequency measurement <
> time-nuts@febo.com>
> >Subject: Re: [time-nuts] Thunderbolt? (re simple gpsdo.)
> >
> >Hi Chris,
> >
> >> I just finished reading about that one. It
I believe those Rockwells have a 10 KHz output. Not a bad price.
73 es HNY, Dick, W1KSZ
-Original Message-
>From: b...@lysator.liu.se
>Sent: Dec 30, 2011 12:42 PM
>To: Discussion of precise time and frequency measurement
>Subject: Re: [time-nuts] Thunderbolt? (re simple g
May I suggest use of small controllers such as the Picaxe series? I find
them very useful around the "lab" for small tasks such as this. Easily
programmed, very reliable, and the software application can be as simple
or complex as needed, for example the suggested PID controller. No
soldering, no f
it-banging, see
www.dlpdesign.com/images/bit-bang-usb.pdf
From: Mark Spencer
To: Discussion of precise time and frequency measurement
Sent: Fri, December 30, 2011 2:13:41 PM
Subject: Re: [time-nuts] Thunderbolt? (re simple gpsdo.)
On a related note is anyone aware o
"What is the simplest design for a GPSDO that uses only the PPS signal
from
a modern GPS?"
Some sort of oscillator with a voltage control.
CPU with a timer/counter that can capture the PPS.
DAC.
Software.
How about MSC1200 : http://www.ti.com/lit/ds/symlink/msc1200y3.pdf
Stanley
__
Hi Chris,
> I just finished reading about that one. It requires no longer
> available GPS reciever. Maybe I should r-phrase the question:
Most of us get (re)used stuff... Ebay #300437642776 has some Rockwell era
receivers. Many time-nuts find HP5065A rubidiums and 5370 counters
available and i
, see
www.dlpdesign.com/images/bit-bang-usb.pdf
From: Mark Spencer
To: Discussion of precise time and frequency measurement
Sent: Fri, December 30, 2011 2:13:41 PM
Subject: Re: [time-nuts] Thunderbolt? (re simple gpsdo.)
On a related note is anyone aware of PC
hing that might
acquired used on an auction site.
--- On Fri, 12/30/11, Hal Murray wrote:
> From: Hal Murray
> Subject: Re: [time-nuts] Thunderbolt? (re simple gpsdo.)
> To: "Discussion of precise time and frequency measurement"
>
> Received: Friday, December 30, 20
> "What is the simplest design for a GPSDO that uses only the PPS signal from
> a modern GPS?"
Some sort of oscillator with a voltage control.
CPU with a timer/counter that can capture the PPS.
DAC.
Software.
Drive the CPU from the osc so you can count cycles between PPS pulses. Use
the DAC t
There is no reason you can not do that.
It is tricky because the low comparison frequency limits the loop
bandwidth like any sampled data system and the analog requirements for
the low frequency design become an issue do to leakage and the
impedance levels needed. The long time constants involved
Yes, it can be done based on a PPS only timing. You must design a PI (maybe
PID) regulator: the EFC must stay steady when the phase difference between
the two PPSes is zero (integral action). Then you must move the EFC (when
there is a difference) proportionally with the difference itself and only
well.
>> >
>> > 73 es HNY, Dick, W1KSZ
>> >
>> >
>> > -Original Message-
>> > From: Mark Spencer
>> > Sent: Dec 29, 2011 9:24 PM
>> > To: Discussion of precise time and frequency measurement <
>> time-nuts@febo.
On Thu, Dec 29, 2011 at 8:24 PM, Mark Spencer wrote:
> One of the designs using the 10 kHz output from a Jupiter gps engine and a
> simple PLL to discipline an ocxo might be good starting point if suitable gps
> engines are still available. There won't be much to tweak but the
> performance co
do other things...
-Original Message-
From: Mark Spencer
Sender: time-nuts-boun...@febo.com
Date: Thu, 29 Dec 2011 20:24:34
To: Discussion of precise time and frequency measurement
Reply-To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Thunderbolt
4 PM
> >> To: Discussion of precise time and frequency measurement <
> time-nuts@febo.com>
> >> Subject: Re: [time-nuts] Thunderbolt? (re simple gpsdo.)
> >>
> >> One of the designs using the 10 kHz output from a Jupiter gps engine
> and a simple PLL to
-Original Message-
>> From: Mark Spencer
>> Sent: Dec 29, 2011 9:24 PM
>> To: Discussion of precise time and frequency measurement
>> Subject: Re: [time-nuts] Thunderbolt? (re simple gpsdo.)
>>
>> One of the designs using the 10 kHz output from a Jupiter gp
: [time-nuts] Thunderbolt? (re simple gpsdo.)
>
>One of the designs using the 10 kHz output from a Jupiter gps engine and a
>simple PLL to discipline an ocxo might be good starting point if suitable gps
>engines are still available. There won't be much to tweak but the performance
One of the designs using the 10 kHz output from a Jupiter gps engine and a
simple PLL to discipline an ocxo might be good starting point if suitable gps
engines are still available. There won't be much to tweak but the performance
could be quite good.
My first gpsdo was a manufactured version
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