Re: [time-nuts] Phase Noise and ADCs

[John Miles]

> To a first order, the ADC is like an ideal multiplier/mixer - phase noise on 
> the
> clock contributes to phase noise on the sampled data by reciprocal mixing, 
> just
> like a mixer.

The ADC-as-mixer metaphor is a useful abstraction, but a leaky one.  Here's the 
way I think of it: while all mixers are multipliers, they fall into two 
distinct categories, 'stateful' and 'stateless.'  Conventional mixers are 
switches with no internal state of their own.  At any given moment they are 
either on or off based on the LO input state, or they exhibit forward or 
reverse conduction in the case of a diode ring or similar balanced structure.  
So their ideal response is dictated solely by the usual Fourier expansion of 
the square-wave LO harmonics including the first.

A harmonic mixer is another stateless mixer, but through topology and component 
selection it is designed to respond best to input signals near even, odd, or 
(if driven by a comb generator) both multiples of the LO frequency.  Still 
subject to Fourier at the end of the day, but with specific workarounds where 
needed.

Now, while a sampler is still a multiplier at heart, some 'state' in the form 
of charge on the sample/hold capacitor is retained from one LO cycle to the 
next.  As a result, unlike a conventional mixer, a sampler's theoretical 
response at higher input frequencies has nothing to do with the Fourier content 
of the LO drive signal, but is instead limited by the hold capacitance and 
external source impedance.  It ends up looking like a sin(x)/x function, 
falling off slowly in general with input frequency but with periodic zeroes 
near LO harmonics >1.

One consequence of charge retention is that when the input signal is in the 
first Nyquist zone, meaning below fLO/2, no net frequency translation occurs in 
a sampler.  There is no mixing going on, hence no reciprocal mixing either.  
The sampler's zero-order hold characteristic passes the captured input signal 
straight through to the output.  Because your ADC's front end is a sampler, 
this is the condition that applies when you digitize a 10 MHz input signal with 
a 122.88 MHz clock.  About 13 times per input cycle, a sample of the 10 MHz 
signal is captured and transferred to the hold capacitance for eventual readout 
on the data bus.  Any jitter that's present on the 122.88 MHz clock will be 
transferred as well, but it will be attenuated by 20*log10(12.288) dB because 
each clock cycle is responsible for capturing only about 1/13 of each input 
cycle. 

Make sense?

-- john, KE5FX
Miles Design LLC


___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] What do people use for measuring temperature?

[Jeremy Nichols]

Do we know what this “Long Term Aging Process” is or is it proprietary?



On Sat, Sep 26, 2020 at 5:03 PM Bruce Griffiths 
wrote:

> Drift ~1-2mK per year for suitably conditioned thermistors at 25C:
>
>
> https://www.littelfuse.com/technical-resources/technical-centers/temperature-sensors/thermistor-info/thermistor-terminology/stability.aspx
>
>
>
> Bruce
>
> > On 27 September 2020 at 11:15 Bob kb8tq  wrote:
>
> >
>
> >
>
> > Hi
>
> >
>
> > Roughly speaking 99.9% of all OCXO’s use thermistors as temperature
> sensors.
>
> > The normal evaluation process on a new one *probably* would catch
> something < 0.01C
>
> > over a few months. You may do it a couple different ways depending on
> the target
>
> > OCXO. The net result is still in the “golly gee wiz low” sort of range.
> If you can detect a
>
> > drift / shift, you disqualify that part and move on to another one. Very
> few glass bead
>
> > parts seem to get tossed out …..
>
> >
>
> > Bob
>
> >
>
> >
>
> >
>
> > > On Sep 26, 2020, at 4:23 PM, John Ponsonby 
> wrote:
>
> > >
>
> > > Have any time-nuts got any data on the long term stability or drift
> rates/ageing characteristics of thermistors? I am concerned with  ability
> of holding temperature constant at the milliK level for years. I reckon
> that if one can measure it one can control it. Conversely if one can't
> measure it, because of the instability of the sensor,  one can't control it.
>
> > > John Ponsonby
>
> > > ___
>
> > > time-nuts mailing list -- time-nuts@lists.febo.com
>
> > > To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>
> > > and follow the instructions there.
>
> >
>
> >
>
> > ___
>
> > time-nuts mailing list -- time-nuts@lists.febo.com
>
> > To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>
> > and follow the instructions there.
>
>
>
> ___
>
> time-nuts mailing list -- time-nuts@lists.febo.com
>
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>
> and follow the instructions there.
>
> --
Jeremy Nichols
Sent from my iPad 6.
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] New member, new old 4040A with PSU failure

[wbeam]

- Original Message -
From: Tom Van Baak 
To: time-nuts@lists.febo.com
Sent: Sat, 26 Sep 2020 20:21:04 -0400 (EDT)
Subject: Re: [time-nuts] New member, new old 4040A with PSU failure




If anyone on the list has experience with rodents, you'll notice the 4th 
photo of the fts4040 link above shows that a mouse nibbled on the pink 
silicone insulation around the HV connections. So be careful where you 
store your old cesium standards. I'm used to bugs in s/w but rats in h/w 
is a new low. What kind of HV goo should I replace it with?

/tvb


avoid peanut butter

Bill Beam NL7F

___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] New member, new old 4040A with PSU failure

[Robert LaJeunesse]

Tom, have a look at "Super Corona Dope"

https://www.mgchemicals.com/products/conformal-coating/insulation-coatings/4226-super-corona-dope/

Bob L.



> Sent: Saturday, September 26, 2020 at 8:21 PM
> From: "Tom Van Baak" 
> To: time-nuts@lists.febo.com
> Subject: Re: [time-nuts] New member, new old 4040A with PSU failure
>
> 
>
> If anyone on the list has experience with rodents, you'll notice the 4th
> photo of the fts4040 link above shows that a mouse nibbled on the pink
> silicone insulation around the HV connections. So be careful where you
> store your old cesium standards. I'm used to bugs in s/w but rats in h/w
> is a new low. What kind of HV goo should I replace it with?
>
> /tvb

___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] New member, new old 4040A with PSU failure

[Tom Van Baak]

Patrick,

Nice find on the PRS10 and Datum/FTS 4040. The cesium is definitely 
worth trying to get working. See if either of these pages help:


http://leapsecond.com/museum/fts4040/

http://leapsecond.com/museum/fts-7504/

The thin red / black wires you speak of are the +24 VDC and +10 VDC 
power *into* the HV modules. The actual HV *output* comes out of those 
special (black & green, or pink) highly insulated connectors. Let us 
know if your 4040A looks anything like what you see in my photos.




If anyone on the list has experience with rodents, you'll notice the 4th 
photo of the fts4040 link above shows that a mouse nibbled on the pink 
silicone insulation around the HV connections. So be careful where you 
store your old cesium standards. I'm used to bugs in s/w but rats in h/w 
is a new low. What kind of HV goo should I replace it with?


/tvb


On 9/25/2020 12:10 PM, Patrick Tanner wrote:

Hi folks.

I'm new to the board, my name is Patrick. I'm a career RF/systems engineer.
Greetings all around!

I just made a couple of 'good' handyman special buys on the worlds largest
auction. I got a PRS10 that needed a new SA612A mixer that I got working,
so, happy about that. Thanks to KO4BB for having the schematics.

I also picked up a FTS4040A, apparently with a failed PSU. Its labelled
'high voltage' , but the dinky 24? 26? Ga output leads (red/black 3x
ganged) don't led me to believe that there' s 2.2kV here. Can any one shed
some light on what this PSUs output is? I'm hoping that I can either fix or
replace it and find a diamond here.

Thanks for your help.
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.




___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Phase Noise and ADCs

[Bob kb8tq]

Hi



> On Sep 26, 2020, at 7:22 PM, Magnus Danielson  wrote:
> 
> Hi John,
> 
> On 2020-09-26 17:10, John Ackermann N8UR wrote:
>> We know that phase noise scales with frequency, so if you multiply
>> frequency by 10 you get a 20 dB increase in noise.
>> 
>> What I don't fully understand is how that relationship works with
>> other than simple multiplication/division.
>> 
>> For example (and my real life concern), if I have an analog to digital
>> converter that is clocked at 122.88 MHz and know the phase noise of
>> that clock signal, what do I know about the effective phase noise when
>> the ADC is receiving a signal at, e.g., 12.288 MHz?
>> 
>> In other words, if I were to measure the phase noise at the output of
>> the ADC when fed a high-enough quality 12.288 MHz signal, would I see
>> something like the 122.88 MHz phase noise, or something better due to
>> the scaling by 10?
> 
> In this case, your 12.288 MHz phase-noise will be augmented with the
> scaled-down version of the 122,88 MHz phase-noise. The trick being used
> is to actually let the sampling clock of the ADC be a transfer clock
> such that it samples a reference also, at which time one subtracts the
> phase-data from the reference, most of the transfer clocks noise cancels
> out, and it does so fairly well as it have common integration time
> between the channels, so you avoid the decorrelation that DMTD normally
> suffers from. The second trick being used is to use a second pair of
> ADCs to make ADC deficiensies cancel out too, as the DUT and REF is
> common mode and the individual ADC noise contributors can be averaged out.
> 

If you are going to do the “cancel out” process, a dual ADC with a common 
clock interface is a really good idea. Not all dual ADC devices have that
feature……

Bob


> Now, as you decimate data etc. you still have the issue of ADC
> resolution, as that has a tendency to loose weak side-bands. The
> non-linearity is kind of peculiar actually.
> 
> I recommend you to dig up Sam Stein's papers on his phase noise
> development. I think you will find them a good read and help you with
> your understanding.
> 
> Cheers,
> Magnus
> 
> 
> 
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to 
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.


___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] What do people use for measuring temperature?

[Bruce Griffiths]

Drift ~1-2mK per year for suitably conditioned thermistors at 25C:
https://www.littelfuse.com/technical-resources/technical-centers/temperature-sensors/thermistor-info/thermistor-terminology/stability.aspx

Bruce
> On 27 September 2020 at 11:15 Bob kb8tq  wrote:
> 
> 
> Hi
> 
> Roughly speaking 99.9% of all OCXO’s use thermistors as temperature 
> sensors. 
> The normal evaluation process on a new one *probably* would catch something < 
> 0.01C
> over a few months. You may do it a couple different ways depending on the 
> target
> OCXO. The net result is still in the “golly gee wiz low” sort of range. If 
> you can detect a 
> drift / shift, you disqualify that part and move on to another one. Very few 
> glass bead 
> parts seem to get tossed out …..
> 
> Bob
> 
> 
> 
> > On Sep 26, 2020, at 4:23 PM, John Ponsonby  wrote:
> > 
> > Have any time-nuts got any data on the long term stability or drift 
> > rates/ageing characteristics of thermistors? I am concerned with  ability 
> > of holding temperature constant at the milliK level for years. I reckon 
> > that if one can measure it one can control it. Conversely if one can't 
> > measure it, because of the instability of the sensor,  one can't control it.
> > John Ponsonby
> > ___
> > time-nuts mailing list -- time-nuts@lists.febo.com
> > To unsubscribe, go to 
> > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > and follow the instructions there.
> 
> 
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to 
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.

___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Phase Noise and ADCs

[Magnus Danielson]

Hi John,

On 2020-09-26 17:10, John Ackermann N8UR wrote:
> We know that phase noise scales with frequency, so if you multiply
> frequency by 10 you get a 20 dB increase in noise.
>
> What I don't fully understand is how that relationship works with
> other than simple multiplication/division.
>
> For example (and my real life concern), if I have an analog to digital
> converter that is clocked at 122.88 MHz and know the phase noise of
> that clock signal, what do I know about the effective phase noise when
> the ADC is receiving a signal at, e.g., 12.288 MHz?
>
> In other words, if I were to measure the phase noise at the output of
> the ADC when fed a high-enough quality 12.288 MHz signal, would I see
> something like the 122.88 MHz phase noise, or something better due to
> the scaling by 10?

In this case, your 12.288 MHz phase-noise will be augmented with the
scaled-down version of the 122,88 MHz phase-noise. The trick being used
is to actually let the sampling clock of the ADC be a transfer clock
such that it samples a reference also, at which time one subtracts the
phase-data from the reference, most of the transfer clocks noise cancels
out, and it does so fairly well as it have common integration time
between the channels, so you avoid the decorrelation that DMTD normally
suffers from. The second trick being used is to use a second pair of
ADCs to make ADC deficiensies cancel out too, as the DUT and REF is
common mode and the individual ADC noise contributors can be averaged out.

Now, as you decimate data etc. you still have the issue of ADC
resolution, as that has a tendency to loose weak side-bands. The
non-linearity is kind of peculiar actually.

I recommend you to dig up Sam Stein's papers on his phase noise
development. I think you will find them a good read and help you with
your understanding.

Cheers,
Magnus



___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] What do people use for measuring temperature?

[Richard (Rick) Karlquist]

The HP E1938A OCXO that I worked on had a feature where
we could set the oven temperature individually on each
oscillator to the exact turnover point of the crystal.
With all the temperature characterization we did, it
would seem like if there were a thermistor "aging"
process, we would have seen it.  However, we
didn't have the resources to proactively search for
it.  The E1938A oven is stable to a fraction of
a milliKelvin, over its rated -55 to +85 degree C spec.
We used three thermistors and averaged them.  They
were basically the same thermistors used in the 10811.
IIRC, we bought them from Yellow Springs.

Rick N6RK

On 9/26/2020 1:23 PM, John Ponsonby wrote:

Have any time-nuts got any data on the long term stability or drift 
rates/ageing characteristics of thermistors? I am concerned with  ability of 
holding temperature constant at the milliK level for years. I reckon that if 
one can measure it one can control it. Conversely if one can't measure it, 
because of the instability of the sensor,  one can't control it.
John Ponsonby
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.



___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] What do people use for measuring temperature?

[Bob kb8tq]

Hi

Roughly speaking 99.9% of all OCXO’s use thermistors as temperature 
sensors. 
The normal evaluation process on a new one *probably* would catch something < 
0.01C
over a few months. You may do it a couple different ways depending on the target
OCXO. The net result is still in the “golly gee wiz low” sort of range. If you 
can detect a 
drift / shift, you disqualify that part and move on to another one. Very few 
glass bead 
parts seem to get tossed out …..

Bob



> On Sep 26, 2020, at 4:23 PM, John Ponsonby  wrote:
> 
> Have any time-nuts got any data on the long term stability or drift 
> rates/ageing characteristics of thermistors? I am concerned with  ability of 
> holding temperature constant at the milliK level for years. I reckon that if 
> one can measure it one can control it. Conversely if one can't measure it, 
> because of the instability of the sensor,  one can't control it.
> John Ponsonby
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to 
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.


___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

[time-nuts] What do people use for measuring temperature?

[John Ponsonby]

Have any time-nuts got any data on the long term stability or drift 
rates/ageing characteristics of thermistors? I am concerned with  ability of 
holding temperature constant at the milliK level for years. I reckon that if 
one can measure it one can control it. Conversely if one can't measure it, 
because of the instability of the sensor,  one can't control it.
John Ponsonby
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] New member, new old 4040A with PSU failure

[paul swed]

Pat
I am familiar with the fts4050. Please send me a pix of what you are
looking at. Best to do this offline.
Thanks Paul.

On Fri, Sep 25, 2020 at 10:46 PM Patrick Tanner  wrote:

> Hi folks.
>
> I'm new to the board, my name is Patrick. I'm a career RF/systems engineer.
> Greetings all around!
>
> I just made a couple of 'good' handyman special buys on the worlds largest
> auction. I got a PRS10 that needed a new SA612A mixer that I got working,
> so, happy about that. Thanks to KO4BB for having the schematics.
>
> I also picked up a FTS4040A, apparently with a failed PSU. Its labelled
> 'high voltage' , but the dinky 24? 26? Ga output leads (red/black 3x
> ganged) don't led me to believe that there' s 2.2kV here. Can any one shed
> some light on what this PSUs output is? I'm hoping that I can either fix or
> replace it and find a diamond here.
>
> Thanks for your help.
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] What do people use for measuring temperature?

[Jeremy Nichols]

Answered my own question: Ametherm ACC-003 from Tim Hughes’ 2-02-2019 post
to the HPAK Equipment group (thanks, Tim!).


On Sat, Sep 26, 2020 at 10:25 AM Jeremy Nichols  wrote:

> The HP-3456A DVM was mentioned as one way to measure temperature with
> thermistors. Does anyone know the specs for the thermistor that the 3456
> can use? All my manual gives is an HP part number.
>
> Jeremy
>
>
> --
> Jeremy Nichols
> Sent from my iPad 6.
>
>
> --
Jeremy Nichols
Sent from my iPad 6.
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Phase Noise and ADCs

[jimlux]

On 9/26/20 9:56 AM, Bob kb8tq wrote:

Hi

In addition, the input to the ADC has it’s own noise issues. If you have a 
really
clean clock (or a poor ADC), the noise floor of the input may dominate the 
noise floor.

Bob



Yes - and typically, this spec is not given in a useful fashion for 
time-nuttery.  You have to test it and see what it is.


for instance, the AD9650 has a specified aperture uncertainty specified 
as jitter of, say, 0.08 picosecond, rms.


And they don't specify what the clock input bandwidth is.





On Sep 26, 2020, at 12:28 PM, jimlux  wrote:

On 9/26/20 8:10 AM, John Ackermann N8UR wrote:

We know that phase noise scales with frequency, so if you multiply frequency by 
10 you get a 20 dB increase in noise.
What I don't fully understand is how that relationship works with other than 
simple multiplication/division.
For example (and my real life concern), if I have an analog to digital 
converter that is clocked at 122.88 MHz and know the phase noise of that clock 
signal, what do I know about the effective phase noise when the ADC is 
receiving a signal at, e.g., 12.288 MHz?


To a first order, the ADC is like an ideal multiplier/mixer - phase noise on 
the clock contributes to phase noise on the sampled data by reciprocal mixing, 
just like a mixer.




In other words, if I were to measure the phase noise at the output of the ADC 
when fed a high-enough quality 12.288 MHz signal, would I see something like 
the 122.88 MHz phase noise, or something better due to the scaling by 10?
Thanks!
John
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.



___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.



___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.




___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] What do people use for measuring temperature?

[Jeremy Nichols]

The HP-3456A DVM was mentioned as one way to measure temperature with
thermistors. Does anyone know the specs for the thermistor that the 3456
can use? All my manual gives is an HP part number.

Jeremy


-- 
Jeremy Nichols
Sent from my iPad 6.
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Phase Noise and ADCs

[Bob kb8tq]

Hi

In addition, the input to the ADC has it’s own noise issues. If you have a 
really
clean clock (or a poor ADC), the noise floor of the input may dominate the 
noise floor. 

Bob

> On Sep 26, 2020, at 12:28 PM, jimlux  wrote:
> 
> On 9/26/20 8:10 AM, John Ackermann N8UR wrote:
>> We know that phase noise scales with frequency, so if you multiply frequency 
>> by 10 you get a 20 dB increase in noise.
>> What I don't fully understand is how that relationship works with other than 
>> simple multiplication/division.
>> For example (and my real life concern), if I have an analog to digital 
>> converter that is clocked at 122.88 MHz and know the phase noise of that 
>> clock signal, what do I know about the effective phase noise when the ADC is 
>> receiving a signal at, e.g., 12.288 MHz?
> 
> To a first order, the ADC is like an ideal multiplier/mixer - phase noise on 
> the clock contributes to phase noise on the sampled data by reciprocal 
> mixing, just like a mixer.
> 
> 
> 
>> In other words, if I were to measure the phase noise at the output of the 
>> ADC when fed a high-enough quality 12.288 MHz signal, would I see something 
>> like the 122.88 MHz phase noise, or something better due to the scaling by 
>> 10?
>> Thanks!
>> John
>> ___
>> time-nuts mailing list -- time-nuts@lists.febo.com
>> To unsubscribe, go to 
>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>> and follow the instructions there.
> 
> 
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to 
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.


___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Phase Noise and ADCs

[jimlux]

On 9/26/20 8:10 AM, John Ackermann N8UR wrote:
We know that phase noise scales with frequency, so if you multiply 
frequency by 10 you get a 20 dB increase in noise.


What I don't fully understand is how that relationship works with other 
than simple multiplication/division.


For example (and my real life concern), if I have an analog to digital 
converter that is clocked at 122.88 MHz and know the phase noise of that 
clock signal, what do I know about the effective phase noise when the 
ADC is receiving a signal at, e.g., 12.288 MHz?


To a first order, the ADC is like an ideal multiplier/mixer - phase 
noise on the clock contributes to phase noise on the sampled data by 
reciprocal mixing, just like a mixer.






In other words, if I were to measure the phase noise at the output of 
the ADC when fed a high-enough quality 12.288 MHz signal, would I see 
something like the 122.88 MHz phase noise, or something better due to 
the scaling by 10?


Thanks!

John



___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com

and follow the instructions there.



___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

[time-nuts] backup power (was BVA has been sold)

[jimlux]

On 9/25/20 11:07 PM, Poul-Henning Kamp wrote:


Bill Notfaded writes:



Can't I just use a high quality APC backup power system like we use to
power racks of gear in our Telco and compute closets?


Very few UPS's are good at long-run applications, they are typically
built to run a heavy load for minutes, not a tiny load for hours
or even days on end.






That means low efficiency, 75% net efficiency is considered good,
and it goes totally south the further you are from the name-plate load,
because the constant overhead is large.

Some UPSs dont even have a thermal design allowing 24*365 operation.



As people have found when modifying those inexpensive $100 UPSes to use 
an external battery.  They're *cost sensitive* so the electronics just 
gets to maximum temperature as the designed in battery runs out.  It 
might be cheaper to add mass than a (noisy) fan, for instance.







If you want to power mains kit from batteries, it is usually better
to get a "real" inverter which is built island-grid applications.



They do make UPSes for long term running but not as a static inverter - 
typically you can identify them because they come with options for 
external batteries. Or,you choose which battery pack to add.






But for powering small loads, OCXO's, GPSDO's, Rb's, fire alarms,
emergency lighting etc, the overhead of going from battery voltage
to mains voltage and back is just a unnecessary loss.




There is, also, the Tesla PowerWall approach..
13.5 kWh, 7kW peak, 5 kW avg, $6500

You can keep a lot of oscillators humming for quite a while with 13.5 
kWh, even at reduced efficiency.



___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Oscilloquartz BVA has been sold. Thank you all who expressed an interest.

[Mark Spencer]

A few decades ago I  worked with some quite large Telecom gear that ran from 
208 volt AC.The equipment had its own internal 48 volt supplies and short 
term battery back up system (basically so the redundant CPU units could 
gracefully shut down in the event of a power failure.)   The manufacturer also 
sold similar systems that ran from customer supplied 48 volts but many 
enterprise customers who already had large UPS systems and back up generators 
preferred the versions that ran from 208 volt AC.   

Some smaller office phone systems back in the early 1990's also featured large 
external battery packs to get multi hour run times.   The vendors would 
typically send technicians out to peridoically check the battery systems.   The 
few that I was able to examine were typically made up from 2 volt sealed lead 
acid cells.   The used cells used to be some what available to hobbyists as the 
tended to get replaced before they failed.

Yes some large UPS systems don't work very well at supplying low levels of 
power for long the periods.   During a multi hour maintenance shut down at work 
a few decades ago we had one device that we hoped to keep running (essentially 
a small digital voice play back unit that played phone system messages, ie. 
"The number you have reached is not in service.")  It drew well under 100 watts 
and was the only load at the time for a large UPS system with multiple battery 
banks which stopped running after a few hours and I had to re record the 
messages.   None of us were very surprised.


Mark Spencer
m...@alignedsolutions.com
604 762 4099

> On Sep 26, 2020, at 12:33 AM, Hal Murray  wrote:
> 
> 
>>> Can't I just use a high quality APC backup power system
>>> like we use to power racks of gear in our Telco and compute closets?
> 
>> Very few UPS's are good at long-run applications, they are typically built to
>> run a heavy load for minutes, not a tiny load for hours or even days on end.
> 
> That matches my expectations, but somebody might expect their telco gear to 
> stay up longer than the few minutes it takes to cleanly shut down a computer.
> 
> Is there a branch of UPS gear aimed at telco rather than computers?  That is 
> good efficiency at low power and long time rather than high power for short 
> time.
> 
> Does all telco gear that is expected to run off UPS take 48V?
> 
> Is there a market in small 48V supplies with UPS option for the telco market? 
>  
> You would have to build a 48V to 24V converter rather than the whole thing.  
> You can probably get a brick for that.
> 
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
> 
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to 
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
> 

___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

[time-nuts] Phase Noise and ADCs

[John Ackermann N8UR]

We know that phase noise scales with frequency, so if you multiply 
frequency by 10 you get a 20 dB increase in noise.


What I don't fully understand is how that relationship works with other 
than simple multiplication/division.


For example (and my real life concern), if I have an analog to digital 
converter that is clocked at 122.88 MHz and know the phase noise of that 
clock signal, what do I know about the effective phase noise when the 
ADC is receiving a signal at, e.g., 12.288 MHz?


In other words, if I were to measure the phase noise at the output of 
the ADC when fed a high-enough quality 12.288 MHz signal, would I see 
something like the 122.88 MHz phase noise, or something better due to 
the scaling by 10?


Thanks!

John



___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] What do people use for measuring temperature?

[Bob kb8tq]

Hi

One interesting “oops” using RTD’s:

They are close cousins of strain gauges. Some RTD designs are *very* close.
Mount them to this or that and they may tell you more about the stress / strain
in the mount than about the temperature. 

You do *not* want to know how many (hundred) temperature test chamber sensors
that particular goof messed up …… 4 sensors per chamber, 8 in a pod, three pods
in the factory here, four pods in the factory down south, Two partials in 
engineering, 
two partials in QA ….

The answer ultimately was to tear out all the RTD’s and replace them with 
carefully
tested (= sorted) AD590’s. 

Bob

> On Sep 26, 2020, at 10:48 AM, Joseph Gwinn  wrote:
> 
> On Fri, 25 Sep 2020 22:46:32 -0400, time-nuts-requ...@lists.febo.com 
> wrote:  Re: time-nuts Digest, Vol 194, Issue 40
> 
> 
>> --
>> 
>> Message: 8
>> Date: Fri, 25 Sep 2020 04:50:35 -0700
>> From: Hal Murray 
>> To: time-nuts@lists.febo.com
>> Cc: Hal Murray 
>> Subject: [time-nuts] What do people use for measuring temperature?
>> Message-ID:
>>  <20200925115035.504af406...@ip-64-139-1-69.sjc.megapath.net>
>> Content-Type: text/plain; charset=us-ascii
>> 
>> 
>> I've got a collection of 1-wire gizmos and USB thumb drives.  They 
>> are great 
>> for many applications but I'm looking for something better/different.
>> 
>> I'd like something that reads to 0.01 degree or 0.001 degree.  I don't need 
>> accuracy.  What I want is reasonable linearity so I can make pretty graphs.
>> 
>> I'd like the actual probe to be small enough so I can poke it 
>> inside gear like 
>> a PC and attach it to a crystal.
>> 
>> I'm looking for a USB or serial connection so I can log the data.
>> 
>> Is there an obvious brand/whatever I should be looking at? thermistor? 
>> thermocouple?  ...
>> 
>> I don't care about a display on the device.  I don't want a logger, 
>> they fill 
>> up.  I want to grab the data on the fly and do my own logging.  
>> (But I'm happy 
>> to use a logger if it will do what I want.)
> 
> Sounds like you need a Platinum RTD (Resistance Temperature Detector) 
> unit of some kind.  Don't be scared by the word Platinum - these need 
> not be terribly expensive, and are widely used in industry.
> 
> These are industrial:
> 
> .
> 
> .
> 
> Many bench DMMs have a RTD input.
> 
> Joe Gwinn
> 
> 
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to 
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.


___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] What do people use for measuring temperature?

[Joseph Gwinn]

On Fri, 25 Sep 2020 22:46:32 -0400, time-nuts-requ...@lists.febo.com 
wrote:  Re: time-nuts Digest, Vol 194, Issue 40


> --
> 
> Message: 8
> Date: Fri, 25 Sep 2020 04:50:35 -0700
> From: Hal Murray 
> To: time-nuts@lists.febo.com
> Cc: Hal Murray 
> Subject: [time-nuts] What do people use for measuring temperature?
> Message-ID:
>   <20200925115035.504af406...@ip-64-139-1-69.sjc.megapath.net>
> Content-Type: text/plain; charset=us-ascii
> 
> 
> I've got a collection of 1-wire gizmos and USB thumb drives.  They 
> are great 
> for many applications but I'm looking for something better/different.
> 
> I'd like something that reads to 0.01 degree or 0.001 degree.  I don't need 
> accuracy.  What I want is reasonable linearity so I can make pretty graphs.
> 
> I'd like the actual probe to be small enough so I can poke it 
> inside gear like 
> a PC and attach it to a crystal.
> 
> I'm looking for a USB or serial connection so I can log the data.
> 
> Is there an obvious brand/whatever I should be looking at? thermistor? 
> thermocouple?  ...
> 
> I don't care about a display on the device.  I don't want a logger, 
> they fill 
> up.  I want to grab the data on the fly and do my own logging.  
> (But I'm happy 
> to use a logger if it will do what I want.)

Sounds like you need a Platinum RTD (Resistance Temperature Detector) 
unit of some kind.  Don't be scared by the word Platinum - these need 
not be terribly expensive, and are widely used in industry.

These are industrial:

.

.

Many bench DMMs have a RTD input.

Joe Gwinn


___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] What do people use for measuring temperature?

[Bob kb8tq]

Hi

Going back a bit to get closer to the original request …..

Indeed a thermistor is the “high resolution” king of the hill when it comes to 
temperature
measurement. Resistance change of 3% (30,000 ppm) per degree is not uncommon, 
you can do better …
They come in all sorts of packages for not a lot of money. eBay will happily 
supply you with 
a ton of parts. Go with high resistance parts to reduce the self heating issues 
mentioned below ….

Since the original request was not concerned about accuracy ( only resolution) 
the cheap
glass body eBay parts may do just fine. You would need to do a bit of 
characterization / 
curve fitting to work out what’s what. 

If you are after 0.001C resolution you would need to measure resistance to 30 
ppm. That
can be done. Indeed a bridge setup and looking at voltage is a more normal way 
to do this.
For narrow ranges an op-amp on the bridge will give you lots of voltage. The 
main issue is
indeed living with the range limitation. 

Yes this is a bit of “cobble it together” nonsense. You can indeed get a pretty 
good setup that
will give you mili C resolution and tens of mili C accuracy. Best guess is that 
a single sensor
system you can trust will be over $5K. The sensors will be giant RTD probes 
that are a bit 
useless for looking at small devices …. sorry about that ….

==

Since this is time nuts ……

One can build an R/C oscillator with a thermistor. You can measure the period 
of the output 
and get temperature that way. Resolution (obviously) is not going to be hard to 
get with a 
Time Nut grade counter. Don’t bother … the jitter is going to get in the way 
long before you get
to 0.01, let alone 0.001C ….

Bob

> On Sep 26, 2020, at 7:18 AM, Manfred Bartz  wrote:
> 
> A thermistor should do the job.  You can buy them in SMD packages and
> down to 0.1% accuracy.
> How much resolution you get depends on the measurement range and the
> ADC you are using.
> 
> A platinum RTD would be another candidate but requires more signal
> conditioning.
> In 3-wire or 4-wire probe configuration you can compensate for long probe 
> wires.
> 
> Any sensor you choose should have a thermal mass less that the item
> you want to measure.
> Generally, a smaller sensor means smaller thermal mass.
> 
> If you really need to resolve 0.01ºC or 0.001ºC then you also need to
> pay attention to:
> * sensor self-heating
> * consider turning off excitation between measurements
> * with a thermistor, go with a high R25,  i.e. 100kΩ which will help
> with keeping self-heating low.
> * Temperature coefficient and environment of the thermistor's series resistor.
> * Stability of the supply/reference voltage.
> 
> BTW, 0.1% resistors are sensitive to static discharge. A zap can
> easily produce a 0.5% change!
> 
> Having really good and stable thermal contact is essential.
> The item you are measuring and the sensor should be in an isolated
> micro environment.
> Airflow or proximity to anything of a different temperature will
> potentially cause a temperature gradient between sensor and the
> measured item.
> 
> All passive temperature sensors require some sort of linearization,
> but that could be done away from the sensor or during post-processing.
> For thermistors search for the "Steinhart Hart equation".
> 
> I am not aware of active (smart) sensors with have better than 0.1ºC
> resolution, but I also have not done any significant search lately.
> 
> Cheers
> --
> Manfred VK3AES
> 
> On Sat, Sep 26, 2020 at 12:46 PM Hal Murray  wrote:
>> 
>> 
>> I've got a collection of 1-wire gizmos and USB thumb drives.  They are great
>> for many applications but I'm looking for something better/different.
>> 
>> I'd like something that reads to 0.01 degree or 0.001 degree.  I don't need
>> accuracy.  What I want is reasonable linearity so I can make pretty graphs.
>> 
>> I'd like the actual probe to be small enough so I can poke it inside gear 
>> like
>> a PC and attach it to a crystal.
>> 
>> I'm looking for a USB or serial connection so I can log the data.
>> 
>> Is there an obvious brand/whatever I should be looking at? thermistor?
>> thermocouple?  ...
>> 
>> I don't care about a display on the device.  I don't want a logger, they fill
>> up.  I want to grab the data on the fly and do my own logging.  (But I'm 
>> happy
>> to use a logger if it will do what I want.)
>> 
>> 
>> --
>> These are my opinions.  I hate spam.
>> 
>> 
>> 
>> 
>> ___
>> time-nuts mailing list -- time-nuts@lists.febo.com
>> To unsubscribe, go to 
>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>> and follow the instructions there.
> 
> 
> 
> -- 
> Manfred  VK3AES
> 
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to 
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.


___
time-nuts 

Re: [time-nuts] AGM Batteries

[Poul-Henning Kamp]

ew via time-nuts writes:

> Sonnenschein has a nice application note on AGM  Learned a lot
> talking with their experts 15 years ago, now retired             
>  http://www.sonnenschein.org/PDF%20files/GelHandbookPart1.pdf    

It used to be possible to find the papers from the annual "BATTCON"
on the web, but it seems that conference has been "commercialized",
and both quality and availability seems to have gone down the drain.

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

[time-nuts] AGM Batteries

[ew via time-nuts]

Sonnenschein has a nice application note on AGM  Learned a lot talking with 
their experts 15 years ago, now retired                
http://www.sonnenschein.org/PDF%20files/GelHandbookPart1.pdf        some trivia 
before Unification Berlin had a huge Sonnenschein Battery Bank to prevent power 
outages.

 Bert Kehren
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] What do people use for measuring temperature?

[Manfred Bartz]

A thermistor should do the job.  You can buy them in SMD packages and
down to 0.1% accuracy.
How much resolution you get depends on the measurement range and the
ADC you are using.

A platinum RTD would be another candidate but requires more signal
conditioning.
In 3-wire or 4-wire probe configuration you can compensate for long probe wires.

Any sensor you choose should have a thermal mass less that the item
you want to measure.
Generally, a smaller sensor means smaller thermal mass.

If you really need to resolve 0.01ºC or 0.001ºC then you also need to
pay attention to:
 * sensor self-heating
 * consider turning off excitation between measurements
 * with a thermistor, go with a high R25,  i.e. 100kΩ which will help
with keeping self-heating low.
 * Temperature coefficient and environment of the thermistor's series resistor.
 * Stability of the supply/reference voltage.

BTW, 0.1% resistors are sensitive to static discharge. A zap can
easily produce a 0.5% change!

Having really good and stable thermal contact is essential.
The item you are measuring and the sensor should be in an isolated
micro environment.
Airflow or proximity to anything of a different temperature will
potentially cause a temperature gradient between sensor and the
measured item.

All passive temperature sensors require some sort of linearization,
but that could be done away from the sensor or during post-processing.
For thermistors search for the "Steinhart Hart equation".

I am not aware of active (smart) sensors with have better than 0.1ºC
resolution, but I also have not done any significant search lately.

Cheers
--
Manfred VK3AES

On Sat, Sep 26, 2020 at 12:46 PM Hal Murray  wrote:
>
>
> I've got a collection of 1-wire gizmos and USB thumb drives.  They are great
> for many applications but I'm looking for something better/different.
>
> I'd like something that reads to 0.01 degree or 0.001 degree.  I don't need
> accuracy.  What I want is reasonable linearity so I can make pretty graphs.
>
> I'd like the actual probe to be small enough so I can poke it inside gear like
> a PC and attach it to a crystal.
>
> I'm looking for a USB or serial connection so I can log the data.
>
> Is there an obvious brand/whatever I should be looking at? thermistor?
> thermocouple?  ...
>
> I don't care about a display on the device.  I don't want a logger, they fill
> up.  I want to grab the data on the fly and do my own logging.  (But I'm happy
> to use a logger if it will do what I want.)
>
>
> --
> These are my opinions.  I hate spam.
>
>
>
>
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to 
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.



-- 
Manfred  VK3AES

___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] What do people use for measuring temperature?

[Tom Van Baak]

This is the document and the correct P/N that Bert meant:

Application Note 3
Applications for a Switched-Capacitor Instrumentation Building Block
Jim Williams, July 1985
page AN3-6, Precision, Linearized Platinum RTD Signal Conditioner

https://www.analog.com/media/en/technical-documentation/application-notes/an03f.pdf 



and

Dual Precision Op Amp (LT1013)

https://www.analog.com/media/en/technical-documentation/data-sheets/LT1013-LT1014.pdf 



/tvb


On 9/26/2020 3:02 AM, ew via time-nuts wrote:

We use a LTC 1013 see LTC Application Note 3 page 6  at least 0.05 C. Good 
enough for us. May still have a board would have to find it, Contact me off 
list. Bert Kehren. In a message dated 9/25/2020 10:46:34 PM Eastern Standard 
Time, hmur...@megapathdsl.net writes:
  I've got a collection of 1-wire gizmos and USB thumb drives.  They are great 
for many applications but I'm looking for something better/different. I'd like 
something that reads to 0.01 degree or 0.001 degree.  I don't need accuracy.  
What I want is reasonable linearity so I can make pretty graphs. I'd like the 
actual probe to be small enough so I can poke it inside gear like a PC and 
attach it to a crystal. I'm looking for a USB or serial connection so I can log 
the data. Is there an obvious brand/whatever I should be looking at? 
thermistor? thermocouple?  ... I don't care about a display on the device.  I 
don't want a logger, they fill up.  I want to grab the data on the fly and do 
my own logging.  (But I'm happy to use a logger if it will do what I want.)  -- 
These are my opinions.  I hate spam.
___time-nuts mailing list -- 
time-n...@lists.febo.comTo unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.comand follow the 
instructions there.
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.




___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Oscilloquartz BVA has been sold. Thank you all who expressed an interest.

[ew via time-nuts]

We have done exactly that not a week at a time because we have enough high 
resolution and did it in 1 Volt steps down to 20 V no change. Current stays the 
same. Bert Kehren In a message dated 9/25/2020 8:44:02 PM Eastern Standard 
Time, p...@phk.freebsd.dk writes: 

Mark Spencer writes:

> The bit I am struggling with re using a 24 volt battery system in this 
> application is what happens when AC power is removed and the terminal
> voltage of the battery  starts to fall.

Don't overengineer your supply (unless you absolutely want to :-)

It looks like the BVA is specified at 24V ±10%, which is 21.6-26.6V.

Nobody says 24 Volt is optimal in that interval, and I have
never been able to measure any difference on any OCXO, as long as
I stayed a few hundred millivolts above the lower limit.

I would run the BVA for a week at 24V, collecting PPS data against
a GPSDO or other suitable source.

Then I would run it for a week at 22V, collecting the same data.

If I could not tell the data from the two runs apart, I would design
a 22V supply.

The BVA is spec'ed at 3W steady state, at 22V that's ~150mA.

In long-run applications you get the name-plate capacity, so two
12V x 15 Ah VRLA blocks would keep your BVA happy for four days,
24Ah would last a week etc.

"Small" come from a lot of dubious manufacturers and which means
badly recycled and impure lead.  For a golfcart that doesn't matter,
but it is a big disadvantage in long-run applications like this.

Saving 5 bucks on lead-acid batteries are usually a bad deal in the
long run, but on the other hand, dont say no if serious battery-people
offer you a couple of pre-owned large batteries cheap, just make
sure you can lift them.

Lead-Acid in long-duration applications should not be discharged much
below 1.85 V, and 12 cells times 1.85V = 22.2 Volt.  Subtract a
diode drop, and now you know where the 24V±10% spec comes from in
the first place.

At 27.6 V float-charge, your linear regulator will have to deal with
(27.6-22)V * 150mA = .84W.

A LM317 would do a fine job, but you can reduce the voltage drop
and get longer runtime with a PNP based home-brew supply.

The float-charger should be able to power the BVA and also recharge
the battery in less than a day, so with 15Ah blocks, I would aim
for around 1-1.5 ampere.

Your batteries will live longer if they have individual chargers,
so something like a 2x12VAC 40-50W torroid trafo, two bridges, two
caps, two LM317's plus resistors and trimpots will do fine.

Poul-Henning

PS: practical hints:

Your local car-nut-emporium has fuseholders like these for cheap:

    
https://www.thansen.dk/bil/udstyr/eludstyr/kontakter-ledning-sikring/sikringer/sikringsholdere/sikringsholder-m.-kabel-fladsikring/n-497642816/pn-1939736599

Take two, crimp ring-lugs on one end of them, and bolt them directly
to the battery terminal:  one for charger, one for load.

When using them next to batteries, the "contra" diode "backwards
across" the LM317 is mandatory.

"Real" UPS installers often have spare batteries which have been
kept on float-charge but otherwise unused, in case of a failure on
customer site.  At end of contract, they dont need them any more.

Telephone people with 2V batteries are interesting too, but their
12V blocks are usually dead by the time the swap them out.

Power-grid people, in particular the nuclear plant people, can also
be a good source very, very good batteries with lots of life in
them still, but be very aware of the weight and the short-circuit
currents.

If you end up with pre-owned liquid electrolyte batteries ("OPzS")
make sure the hydrogen gas can vent safely out of the building.

-- 
Poul-Henning Kamp      | UNIX since Zilog Zeus 3.20
p...@freebsd.org        | TCP/IP since RFC 956
FreeBSD committer      | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.

___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Oscilloquartz BVA has been sold. Thank you all who expressed an interest.

[ew via time-nuts]

Victron Energy has a nice application book on their web site the have super 
products, I used them on my 64 foot GOFAST. Besides products they also discuss 
battery technologies and applications. My hard copy is 15 years old. Here is 
the link in English          
https://www.victronenergy.com/upload/documents/Book-Energy-Unlimited-EN.pdf     
                                  Bert Kehren In a message dated 9/25/2020 
9:02:32 PM Eastern Standard Time, p...@phk.freebsd.dk writes: 

Bob kb8tq writes:

> Two basic types of SLA / VRLA batteries out there: AGM and Gel. For the AGM 
> variety, you want a bit more to your charger.

Yes, if you buy batteries for N * 100K $money, spending more money
on your charger is a good investment.

But if you have two batteries doing float-charge/long-run/tiny-load,
in a benign environment in a corner of your lab, the internal
variance between batteries in that same production lot, will
overshadow any imaginable benefit a fancy charger could bring.

>I haven't worked with Gel cells in a while so they may indeed be easier.

They are for the same reasons they suffer cyclic use better.

But for a float/long-run application, it makes absolutely no difference.

-- 
Poul-Henning Kamp      | UNIX since Zilog Zeus 3.20
p...@freebsd.org        | TCP/IP since RFC 956
FreeBSD committer      | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.

___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] What do people use for measuring temperature?

[ew via time-nuts]

We use a LTC 1013 see LTC Application Note 3 page 6  at least 0.05 C. Good 
enough for us. May still have a board would have to find it, Contact me off 
list. Bert Kehren. In a message dated 9/25/2020 10:46:34 PM Eastern Standard 
Time, hmur...@megapathdsl.net writes: 
 I've got a collection of 1-wire gizmos and USB thumb drives.  They are great 
for many applications but I'm looking for something better/different. I'd like 
something that reads to 0.01 degree or 0.001 degree.  I don't need accuracy.  
What I want is reasonable linearity so I can make pretty graphs. I'd like the 
actual probe to be small enough so I can poke it inside gear like a PC and 
attach it to a crystal. I'm looking for a USB or serial connection so I can log 
the data. Is there an obvious brand/whatever I should be looking at? 
thermistor? thermocouple?  ... I don't care about a display on the device.  I 
don't want a logger, they fill up.  I want to grab the data on the fly and do 
my own logging.  (But I'm happy to use a logger if it will do what I want.)  -- 
These are my opinions.  I hate spam.
___time-nuts mailing list -- 
time-n...@lists.febo.comTo unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.comand follow the 
instructions there.
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Oscilloquartz BVA has been sold. Thank you all who expressed an interest.

[Poul-Henning Kamp]

Hal Murray writes:

> > Very few UPS's are good at long-run applications, they are typically built 
> > to
> > run a heavy load for minutes, not a tiny load for hours or even days on 
> > end. 
>
> That matches my expectations, but somebody might expect their telco gear to 
> stay up longer than the few minutes it takes to cleanly shut down a computer.

Real Telco gear runs from -48VDC fed from, literally, tons of lead-acid 
batteries.

Google "telco battery room" pictures if you dont belive me.

Incidentally, the best batteries for this kind of application are literally
called "circular telco batteries", and almost all of them are still in use,
some of them pushing 50 years now:

https://archive.org/details/bstj49-7-1253/page/n23/mode/2up

> Does all telco gear that is expected to run off UPS take 48V?

In the sense that telcos rarely buy anything but -48VDC kit:  Yes.

> Is there a market in small 48V supplies with UPS option for the telco market? 
>  
> You would have to build a 48V to 24V converter rather than the whole thing.  
> You can probably get a brick for that.

All of 12, 24 and 48VDC are commonly used, and IMO most timing kit is 24VDC.

24VDC is also popular in industrial control settings, for instance:


https://www.pulspower.com/products/supplementary-units/dc-ups-and-buffer-modules/

It's expensive and good, but these days almost all of it is switch-mode.

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Oscilloquartz BVA has been sold. Thank you all who expressed an interest.

[Greg Maxwell]

On Sat, Sep 26, 2020 at 7:36 AM Hal Murray  wrote:

>
> >> Can't I just use a high quality APC backup power system
> >> like we use to power racks of gear in our Telco and compute closets?
>
> > Very few UPS's are good at long-run applications, they are typically
> built to
> > run a heavy load for minutes, not a tiny load for hours or even days on
> end.
>
> That matches my expectations, but somebody might expect their telco gear
> to
> stay up longer than the few minutes it takes to cleanly shut down a
> computer.
>
> Is there a branch of UPS gear aimed at telco rather than computers?  That
> is
> good efficiency at low power and long time rather than high power for
> short
> time.
>
> Does all telco gear that is expected to run off UPS take 48V?
>

48VDC is common. Historically facilities that provide highly available AC
usually do so via generator. The UPSes just need to last long enough for
the generators to start.

Keep in mind that during a long run HVAC needs to be supported too.
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Oscilloquartz BVA has been sold. Thank you all who expressed an interest.

[Hal Murray]

>> Can't I just use a high quality APC backup power system
>> like we use to power racks of gear in our Telco and compute closets?

> Very few UPS's are good at long-run applications, they are typically built to
> run a heavy load for minutes, not a tiny load for hours or even days on end. 

That matches my expectations, but somebody might expect their telco gear to 
stay up longer than the few minutes it takes to cleanly shut down a computer.

Is there a branch of UPS gear aimed at telco rather than computers?  That is 
good efficiency at low power and long time rather than high power for short 
time.

Does all telco gear that is expected to run off UPS take 48V?

Is there a market in small 48V supplies with UPS option for the telco market?  
You would have to build a 48V to 24V converter rather than the whole thing.  
You can probably get a brick for that.



-- 
These are my opinions.  I hate spam.




___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Oscilloquartz BVA has been sold. Thank you all who expressed an interest.

[Poul-Henning Kamp]

Bill Notfaded writes:

>
> Can't I just use a high quality APC backup power system like we use to
> power racks of gear in our Telco and compute closets?

Very few UPS's are good at long-run applications, they are typically
built to run a heavy load for minutes, not a tiny load for hours
or even days on end.

That means low efficiency, 75% net efficiency is considered good,
and it goes totally south the further you are from the name-plate load,
because the constant overhead is large.

Some UPSs dont even have a thermal design allowing 24*365 operation.

If you want to power mains kit from batteries, it is usually better
to get a "real" inverter which is built island-grid applications.

But for powering small loads, OCXO's, GPSDO's, Rb's, fire alarms,
emergency lighting etc, the overhead of going from battery voltage
to mains voltage and back is just a unnecessary loss.

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.