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ehydra | 23 May 20:12
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Impedance measurement fitting algorithm

Hi time-nuts!

If I remember correctly here was a discussion about an older HP 
impedance measurement equipment. The one which is able to calculate a 6 
ideal parts replacement circuit for the measured passive device.

How does is it works? I would like to fit parts for simulation in SPICE. 
So I need something like a algorithm to fit for minimum error a input 
table with complex numbers (frequency-sweep) to this 6 part circuit. For 
example the universal capacitor component in LTspice is able to hold RLC 
and even XTAL data and more like residual current for electrolytics.

Any ideas?

Thanks -
Henry

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Dan Kemppainen | 23 May 14:10

Re: time-nuts Digest, Vol 94, Issue 120

I've had really good luck with anything based on the FTDI chip set. 
Other chip sets have
given me problems...

Dan

On 5/22/2012 6:37 PM, time-nuts-request@... wrote:
> I have yet to be happy with any USB to serial conversion in legacy
> applications.  They always end up less than transparent so instead I
> end up building a legacy PC from old and new parts.
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Hal Murray | 23 May 10:54

Re: Serial port server .. any interest in a write up on using ?


attila@... said:
> On an ethernet it looks quite different:

[snip lots of low jitter samples]

> Network is a destkop - switch1 - switch2 - ntp box.

> The switches are two Level1 Gbit smart switches. The desktop is a ~4y old
> Xeon 2GHz system with a Gbit interface The ntp box is a AMD Geode LX 500MHz
> system with a 100MBit interface Both running linux.

> There aren't noticable more jitter for moderate (1-2 MByte/s) traffic.
> (Probably visible if i would do a statistical analysis...but..) 

1-2 megabytes/sec is 8-16 megabits/sec.  You won't get into serious troubles 
until you saturate a link.  With modern CPUs, it's trivial to saturate 100 
megabit links and not very hard to saturate 1 gigabit links.

With older/slower CPUs, you might run into problems a lot sooner.

I'm not trying to discourage using these boxes.  Just don't be surprised when 
you run into quirks if you are trying to use them for timing.  (and don't 
depend upon loud mouths like me to point out all possible ways they can screw 
up)

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Kim, VK5FJ | 23 May 05:37
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NTP latency monitoring

Hi guys,

About 40 minutes in ESR talks about bufferbloat and NTP skew issues;

   https://plus.google.com/118131797905622113230/posts/FBTdvYhR8qS

Anyone tinkered with measuring GPSd, NTPd and network delay tomography?

regards,

Kim
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Hal Murray | 23 May 02:28

Re: Serial port server .. any interest in a write up on using ?


lists@... said:
> I'd bet at least a cold order of french fries that you would be below 1 ms
> on a modern home wired LAN. Certainly everything I ping locally is sub 1 ms
> unless wireless is involved.

The delay doesn't matter much.  You can correct for it.  I can measure sub ms 
even over a wifi link.

The jitter will be the problem.  That will depend upon the load and your 
setup.

Here is an interesting sample:

64 bytes from xo-c2 (192.168.1.105): icmp_seq=7 ttl=64 time=1.66 ms
64 bytes from xo-c2 (192.168.1.105): icmp_seq=8 ttl=64 time=1.63 ms
64 bytes from xo-c2 (192.168.1.105): icmp_seq=9 ttl=64 time=1.58 ms
64 bytes from xo-c2 (192.168.1.105): icmp_seq=10 ttl=64 time=49.2 ms
64 bytes from xo-c2 (192.168.1.105): icmp_seq=11 ttl=64 time=67.9 ms
64 bytes from xo-c2 (192.168.1.105): icmp_seq=12 ttl=64 time=1.59 ms
64 bytes from xo-c2 (192.168.1.105): icmp_seq=13 ttl=64 time=1.58 ms
64 bytes from xo-c2 (192.168.1.105): icmp_seq=14 ttl=64 time=63.6 ms
64 bytes from xo-c2 (192.168.1.105): icmp_seq=15 ttl=64 time=50.0 ms
64 bytes from xo-c2 (192.168.1.105): icmp_seq=16 ttl=64 time=1.64 ms
64 bytes from xo-c2 (192.168.1.105): icmp_seq=17 ttl=64 time=1.71 ms

Note that 4 samples are way off scale.  The target machine is idle, but the 
packets are going over a wifi link that has other traffic but is far from 
overloaded.  Yes, this is wifi rather than a simple ethernet switch.
(Continue reading)

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Sam | 23 May 01:06
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Re: Serial port server .. any interest in a write up on using ?

Its interesting that this subject has come up. I use IP enabled serial ports daily to communicate to various
remote RF devices that I have installed for work using the built-in serial bridge on the Mikrotik routers
and also on the Barix IP audio decoders/receivers.  As an experiment I had no problems accessing my
Nortel 
GPSTM with one, but I was not able to program a Picaxe.

In my case I use my own software to communicate to the devices as it really is just a simple socket connection 
but if I need a "real" virtual serial port then I use http://www.eterlogic.com/Products.VSPE.html
which works amazingly well. I even wrote a Python script which allows me to access the remote RF gear from
the terminal on my Nokia phone.

The other day I went on the hunt for a dedicated serial/IP converter for a project and found small OEM style
module for $29 US.  #230623218564 at the usual place.

//Sam
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Hal Murray | 22 May 22:44

Re: Serial port server .. any interest in a write up on using ?


ed_palmer@... said:
> I've played with a Lantronix single port server and a Digi 16 port  server
> with no problems for simple COM port emulation.  But I wonder if  they would
> work well with an NTP server.  Has anyone tested that?  Is  the network
> delay a problem due to either amount of delay or variation  in the delay? 

I haven't done the experiment.

If your network is lightly loaded, there shouldn't be much jitter.  All bets 
are off if your network is overloaded.

I think it depends upon your goal.  If your target is a few 10s of ms, I'd 
expect them to work.  If your target is a few microseconds, I'd expect 
problems.

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Hal Murray | 22 May 20:16

Re: Re Serial Port Server


bdsysco@... said:
> I would not recommend building up a computer with numerous serial cards, as
> this solution is not as flexible.

One advantage of serial cards is much better timing.

It's also one less box that has to be working in order to get data.

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BD Systems Inc. | 22 May 18:25
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Re Serial Port Server

Serial Port Servers provide many advantages over serial port cards installed in a computer.  More than
one computer on the network can access a serial port, though not simultaneously, and access can occur over
a wireles network.  Two serial port servers I have and use are the Digi Portserver TS 16 and the Comtrol
Devicemaster.  Each of these Serial Port Servers utilize an ethernet connection, are 1 rack unit (RU),
appear as installed serial ports on each installed computer, have 16 serial ports, and require no
installed operating system.  These can be obtained at reasonable prices on auction sites.  I would not
recommend building up a computer with numerous serial cards, as this solution is not as flexible.
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Bert, VE2ZAZ | 22 May 18:15
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Datum ExacTime 6000

Hi,

I have just acquired a Datum ExacTime 6000 GPS Time Code And Frequency Generator. So far, I am impressed how
fast this unit has stabilized into the low 10e-11 accuracy range... I verify this against the CHU station
carrier (located 15 Km away) . The version of ExacTime 6000 I have is equipped with an OCXO mounted on the
motherboard. The former owner told me that the unit had been upgraded to fix an IRIG B format issue. I cannot
find the info on that upgrade. 

So I have the following questions:

- What is the general impression on the performance of this ExacTime 6000 box?

- The SELECT MODE menu shows possible selections as AUTO, 1SV4, 2SV4, 3SV4, FW or something close to that (I
go by memory)... but the manual provided by Symmetricom suggests selections as Auto, STATIONARY,
DYNAMIC, FW... I would like to set it to stationary. What selection should I make?
- The latest manual provided by Symmetricom is version 8500-0105. Is there a newer manual available?
- I saw a claim that there is a Windows software to manage the device. Where can I get it?
- I tried to output the 1PPS signal throught he rear BNCs. I can set all rates from 10MHz down to 0.1Hz, but I
don't see anything triggering on the scope when I set it to 1PPS. Am I missing something here?

I hope this is not too much work. I would appreciate any assistance, even partial, with these questions.

Thanks in advance,

Bert, VE2ZAZ
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Jerry Mulchin | 22 May 05:51
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Re: Serial port server .. any interest in a write up on using ?


Ditto for me......

Jerry

At 08:16 PM 5/21/2012, you wrote:
>I would be interested in some more information.  I've got quite a few RS232
>devices as well and not nearly enough ports even if I used all my computers.
>
>Alan
>
>On Mon, May 21, 2012 at 8:55 PM, Pete Lancashire <pete@...>wrote:
>
>> Like many time-nuts I have quite a few devices that communicate to the
>> outside world with a serial port. And like many I have more then one.
>> In a past life I use to have to connect to sometimes a 100 RS232 in
>> one location. A popular device is called a terminal server or
>> concentrator. They would take from 1 to 48 RS232 ports on one side and
>> let you talk to them via an Ethernet interface. I so far have twelve
>> RS232 ports in use.
>>
>> ...
>
>So if this is of interest to anyone I'll go into more detail, models, setup
>> etc.
>>
>> -pete
>>
>> -pete
>>
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Gmane