[time-nuts] Telecom Solutions DCD Cesium
Robert Lutwak
Lutwak at Alum.mit.edu
Sun Mar 19 07:34:43 EST 2006
Monitor3 will periodically poll and save the status data to disk for you.
See the File->Unit Monitoring Panel. It also has some very cool
plotting/analysis features (try View->Plot). You can learn a lot about your
unit by watching the dynamics of the boot sequence. Grab the data to disk
with Monitor3 and go back and look at the plots.
The old modules were 5045, which was later renamed 4201A. Some of the last
modules (maybe >2004) were named 4201B and had a new CsIII-based servo
board. Also, if you get a 4201A serviced, depending on the failure, they
may upgrade the servo to a 4201B servo board. Monitor3 can tell them apart.
Also the servo boards have different part numbers and the new one (4201B)
has a big Xilinx CPLD hanging off the microprocessor.
I'm not sure how much of Monitor3 will work with your older unit. I wrote
it to work with the new CsIII-based units and later went back and cobbled in
support for the old 5045/4201A instruments for the guys in technical
service. The telemetry was originally designed to work with a dedicated
stand-alone Sercel terminal (which has been obsolete for at least 15 years).
The old Monitor program (which you may be able to find out there somewhere
in cyberspace) only ran in a terminal emulator which only ran on native DOS
machines, i.e. it wouldn't run in a DOS window under Windows, because it did
low-level serial port control.
I think Monitor3's serial port control functions should work with your 5045,
so if you get tired of 2400 baud, you should be able to crank it up to 9600
from the System->RS232 menu.
In order to get the 03 alarm, you must have made it through all of the
earlier boot sequence, so you must have plenty of signal level, good
microwaves, etc. Without more information I would guess that your unit
either:
a) Problem in C-field control circuit such that DAC is demanding more
current but atoms don't seem to respond.
b) Short in one (or more) of the coils inside the tube so that current
control gets to limit without locking
c) Tube has become magnetized so the Zeeman line asymmetry is big enough
that it tries to lock on the wrong peak.
Watch the "Zeeman Signal Level" during boot (before it throws the alarm).
It should be about the same as the "Clock Signal Level." If it's much lower
(in the neighborhood of zero), than you've got no C-Field in the tube,
either the supply is failed or the coils are shorted out (badly).
If you have Zeeman Signal, next watch the "Zeeman Rabi Innovation" during
boot. After the clock's done initializing the clock and gain servos, it'll
try to acquire lock on Rabi Zeeman. You should see this number start
relatively high (maybe a couple of hundred either +/-) and then you should
see the "C-field current" and the "current-control voltage" change as Zeeman
Rabi is driven to zero. If this succeeds, than all of your electronics (and
most of your tube) is working fine.
Once it acquires lock on Zeeman Rabi, it'll try to hone in on "Zeeman
Ramsey." You'll see the Zeeman Ramsey error suddenly appear (at probably
+/- 500 or so). Then the C-field current will keep changing to try to drive
this one to zero. If all is well, this is the final step of lock. If the
tube is magnetized, enough that you try to lock to the wrong Zeeman Ramsey
peak, you will see the Zeeman Rabi Innovation start to creep back upwards as
you hone in on (the wrong) Zeeman Ramsey. In this state, it will eventually
kick out an 03 alarm, and possibly an 05 as well. This is typically caused
by exposure to high magnetic fields and is fixed by degaussing the tube.
By the way, we just finished re-writing the manuals for the CsIII and
Cs4000. The new manuals include a new Theory-of-Operation section (by me),
which you may find useful. It's not the same electronics as your 5045, but
the physics and the CBT are the same. You can get the manuals off the symm
WWW site.
-RL
------------------------------------------------------------
Robert Lutwak, Senior Scientist
Symmetricom - Technology Realization Center
34 Tozer Rd.
Beverly, MA 01915
(978) 232-1461 Voice RLutwak at Symmetricom.com (Business)
(978) 927-4099 FAX Lutwak at Alum.MIT.edu (Personal)
(339) 927-7896 Mobile
----- Original Message -----
From: "Magnus Danielson" <cfmd at bredband.net>
To: <time-nuts at febo.com>; <Lutwak at alum.mit.edu>
Sent: Sunday, March 19, 2006 6:32 AM
Subject: Re: [time-nuts] Telecom Solutions DCD Cesium
> From: Magnus Danielson <cfmd at bredband.net>
> Subject: Re: [time-nuts] Telecom Solutions DCD Cesium
> Date: Sun, 19 Mar 2006 11:31:11 +0100 (CET)
> Message-ID: <20060319.113111.46845069.cfmd at bredband.net>
>
>> From: "Robert Lutwak" <Lutwak at Alum.mit.edu>
>> Subject: Re: [time-nuts] Telecom Solutions DCD Cesium
>> Date: Sat, 18 Mar 2006 07:47:18 -0500
>> Message-ID: <000501c64a8a$17b46b40$ca1b10ac at lutwakhome>
>>
>> > One more thing...
>> >
>> > Some of the older 5045 modules had badly implemented hardware
>> > handshaking on
>> > the RS-232. Sometimes it helps to wire RTS to CTS in the connector of
>> > your
>> > RS232 cable which attaches to the cesium module. In any case, it never
>> > hurts.
>>
>> Well, now I run a Rx & Tx null-modem cable and operate the Monitor
>> program at
>> 2400 baud and that did the trick. It identifies itself as
>> Symmetricom model 4201A S/N 2116 and the S/N matches what the unit says.
>
> Unscrewing the bottom uncovered the bottom part of the Cesium platform.
> There
> the DATUM model 4021A label is clearly shown. The 4021A platform is made
> year 2000 week 19 and the DCD frame is done in year 2000 week 20. The
> EPROM of
> the control-computer says 5045. Digging on the net the 5045 module shows
> up
> and looks to be the same unit.
>
> Considering that there is a number of soft configuration parameters in
> there,
> I am considering that one of these may be at fault, forcing the loop out
> of
> lock. I am considering writing a small program that allows me to continous
> dump
> and control the cesium status. I have a UNIX box sitting there on the same
> UPS
> and it is just dying for doing this task. However, I am starting to run
> out of
> serial ports! :P Maybe I should have that second computer there anyway.
>
>> It starts of with alarm 16, then tosses alarm 03 and then alarm 05.
>
> I have now also seen alarm 02, Voltage difference (symmetry check of clock
> transition) > 40 mV or Voltage difference (clock pedestal) > 40 mV.
>
>> Looking in the 4065c manual (page 48) this means:
>>
>> 16: Unit restart
>> 03: Voltage difference (Zeeman pedestal) > 160 mV
>> 05: C-field current < 17 mA or > 20 mA
>>
>> The first one is natural when just powered on/cycled.
>>
>> The next one it reads numbers like 220 mV (the highest I recall, but I
>> was not
>> paying attention to that number this round, so I will monitor it more
>> closely).
>
> I might have looked on the wrong numbers here... so please silently ignore
> if
> it does not make sense.
>
> Cheers,
> Magnus
>
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