Datum 4310A Operations Guide

OPERATING MANUAL

Datum 4310A

Cesium Frequency Standard

FTS Part Number: 13894 -201
Revision: C

Printed: November 14, 2001
Copyright 2000 by:
DATUM-Timing, Test & Measurement. 34 Tozer Road, Beverly, MA 01915
phone: [phone] fax: [phone]

TABLE OF CONTENTS

DECLARATION OF CONFORMITY
CERTIFICATE OF CONFORMANCE

SECTION 1. GENERAL INFORMATION................................................................................................1-1

1.1 INTRODUCTION ......................................................................................................................1-1

1.2 SUMMARY DESCRIPTION.....................................................................................................1-1

1.3 INSTRUMENT IDENTIFICATION ..........................................................................................1-1

1.4 PREPARATION FOR SHIPMENT ...........................................................................................1-4

1.5 INSTALLATION........................................................................................................................1-4

1.5.1 Mounting......................................................................................................................1-4

1.5.2 Power Connection.........................................................................................................1-4

1.5.3 Alarm Connections .......................................................................................................1-4

1.5.4 RS232 Connections.......................................................................................................1-5

1.5.5 Safety Considerations ..................................................................................................1-5

1.5.6 Cleaning .......................................................................................................................1-6

TABLE 1-1 SPECIFICATIONS, Cesium Frequency Standard ...............................................................1-2

TABLE 1-2 RS232/ALARM CONNECTIONS.........................................................................................1-4

DATUM Cesium Frequency Standard SECTION 1
GENERAL INFORMATION

SECTION 1. GENERAL INFORMATION

1.1 INTRODUCTION

The Cesium Frequency Standard compares the
frequency of a stable crystal oscillator with the
resonant frequency of the cesium atom. This manual
contains detailed performance and installation
specifications (Section 1), Operating Procedures
(Section 2) and Commands (Section 3) for the Cesium
Frequency Standard.

1.2 SUMMARY DESCRIPTION

The new Datum CsIII represents a leap forward in
terms of making Cesium Beam Frequency Standard
technology available to an ever increasing base of
demanding users in communications, timing,
synchronization and other applications.

The Datum CsIII is the world's smallest and most
economical solution for critical applications requiring
the extraordinary accuracy, stability, and independence
that only cesium based instruments can provide.
Housed in a 2U high, 19 inch rack mount ing package,
the Datum Cesium III weighs only 22 pounds (10kg).

Datum CsIII provides 5MHz and 10MHz RF sine
wave outputs together with a 1 PPS output. In addition,
the unit includes comprehensive system monitoring and
control via a standard RS232 port.

Datum's comprehensive product offerings provide
solutions that address the need for distribution and
alternative outputs. These rack mount or bench top
products include units for RF frequency conversion, RF
distribution, 1 PPS distribution and synthesizers
to provide a range of signals.

A complete list of performance characteristics is
provided in Table 1-1.

1.3 INSTRUMENT IDENTIFICATION

The instrument model name is Datum 4310A Cesium
Frequency Standard—CsIII.

1-1

DATUM Cesium Frequency Standard SECTION 1
GENERAL INFORMATION

TABLE 1 -1 SPECIFICATIONS, Cesium Frequency Standard (at 25 °C unless otherwise specified)

• PERFORMANCE PARAMETER

Accuracy

Warm-up Time (typical)
Reproducibility
Stability

•

Averaging Time (s)
100
101

102

*10

3

*104

*105

*floor

SSB Phase Noise Offset (Hz)
100
101

102

103
104
105

Settability

Range
Resolution
Control

•

• Panel Indicators

Power
Lock
Alarm

100% verified & calibrated against FTS in-house standard.

Green LED indicates there is power to the instrument
Green LED indicates proper operation.
Red LED indicates the improper operation

• Power Requirements AC •• RF Outputs

Operating Voltage 85 to 265 V Frequency 1 each 5 MHz & 10 MHz
Amplitude 1 Vrms
Frequency Range 47 to 63 Hz Harmonic <-40 dBc
400 Hz Spurious <-80 dBc
Power Connector type BNC
(operating) 110 VA, 65 W, 0.6 A @ 115 V Load Impedance 50 ohms
(warm-up) 140 VA, 90 W, 0.8 A @ 115 V Location rear panel

• Dimension ••1 PPS Output

Height 3.50” (88.9 mm) Frequency One pulse per second
Width (front panel) 19.00” (483 mm) Amplitude/wave shape >3.0 V pk into 50 ohms

(instrument) 17.31” (440 mm) Width 20 µs
Depth 15.0” (381 mm) Rise Time <5 ns
Jitter <1 ns rms

• Weight ≈28 lbs (≈13 kg) Connector type BNC

Location rear panel

<2.0E -12

30 min

<1.2E -12

Allan Deviation

<1.2E -11
<8.5E -12
<2.7E -12
<8.5E -13
<2.7E -13
<8.5E -14
<5.0E -14

5MHz

<95 dBc
<130 dBc
<145 dBc
<155 dBc
<155 dBc
<155 dBc

±1E -9
1E -15

via RS232 port

*excluding environmental effects

1-2

DATUM Cesium Frequency Standard SECTION 1
GENERAL INFORMATION

TABLE 1 -1 SPECIFICATIONS, Cesium Frequency Standard (at 25 °C unless otherwise specified)
(cont=d)

GENERAL

Mating Connectors

RS232 (rear panel, DTE) 9 pin male D-connector

(mate: DA9S, ITT Cannon or equal)

ALARM RELAY 9 pin female D-connector

(mate: DA9P, ITT Cannon or equal)
Chassis Ground #8 x .43" stud with 8-32 nut
1 PPS, 10, 5 MHz Outputs BNC, rear panel

Fuses

AC Input – F1, F2 T 1.0 A/250 V for 100 to 140 V ac, 50 to 60 Hz

T 0.5 A/250 V for 210 to 250 V ac, 50 to 60 Hz

Environment
Operating
Temperature 0 to 50°C,
Humidity 95% up to 50°C

Non-operating (transport)
Temperature (storage) -30 to +70°C
(short -term) -40 to +75°C

Magnetic field 0 to 2 gauss

Shock 30 g/11 ms, 3 axis

Vibration MIL-STD-167-1

Altitude (operating) 0 to 50,000 ft

1-3

DATUM Cesium Frequency Standard SECTION 1
GENERAL INFORMATION

1.4 PREPARATION FOR SHIPMENT
To turn off Cesium Frequency Standard prior to
shipment, remove ac power and all other connections.
Package the instrument in its original packing if
possible. If returning the instrument to Datum –
TT&M, contact the service department at (978)927­8220 to let them know it is being returned and the unit=s
serial number.

1.5 INSTALLATION

1.5.1 Mounting
The Cesium Frequency Standard is designed to be
mounted in a standard 19-inch equipment rack and take
up 2 UI of vertical space
(3.5 A).

1.5.2 Power Connection and Fuses
The Cesium Frequency Standard is powered from an ac
source by a detachable power supply cord. This
instrument input connector is the disconnect device.
The ac fuse (and a place for a spare) is located in the ac
connector on the rear panel. The fuse may be checked
or changed by removing the power cord, and gently
prying open the fuse tab on the ac connector. Refer to
Table 1-1 for power supply and fuse requirements.

1.5.3 Alarm Connections
The Cesium Frequency Standard provides for an
ALARM (operation has been or soon will be
compromised). One set of form-C relay contacts is
provided on the 9-pin connector labeled ALARM.
Refer to Table 1-2.

1-4

DATUM Cesium Frequency Standard SECTION 1
GENERAL INFORMATION

1.5.4 RS232 Connection
The Cesium Frequency Standard has one standard 9­pin RS232 connection. Pin-outs are listed in Table 1-2.

TABLE 1-2 RS232/ALARM CONNECTIONS

PIN

1

(DTE, male)

RS232

ALARM

(FEMALE)

+12 V EXT OPTION
2
3
4
5
6
7
8
9

RXD
TXD

DTR

GND

RTS

+12 V RETURN (GROUND)

MAJOR (COMMON)

MAJOR(FAULT=CLOSED)

MAJOR(FAULT=OPEN)

1.5.5 Safety considerations
NOTE: This instrument must be operated only as specified by
the manufacturer. Use, other than as specified, may
compromise the safety precautions of the system.

NOTE: To disconnect power to this instrument, remove the ac
power cord from the rear panel. This is the disconnect device –
there is no ON/OFF switch.

WARNING: For continued protection against risk of fire,
replace only with same type and rating fuse. Fuse
specifications are contained in Table 1-1 and the yellow label
on the unit’s rear panel. Refer to paragraph 1.5.2 for fuse
replacement instructions.

WARNING: Covers on this instrument must not be removed
except by trained service personnel.

1-5

DATUM Cesium Frequency Standard SECTION 1
GENERAL INFORMATION

1.5.6 Cleaning

This instrument may be cleaned while in operation with
a clean, dry cloth. If further cleaning is required, turn
the instrument off, clean with a damp cloth and mild
detergent, and wipe with a dry cloth.

1-6

DATUM Cesium Frequency Standard SECTION 2

OPERATION

SECTION 2. OPERATION

2.1 INTRODUCTION
This section describes procedures for turn-on, turn-off, and
using the DATUM Cesium Frequency Standard.

2.2 TURN-ON PROCEDURE

1) Plug in the Cesium Frequency Standard.

2) Observe that the POWER and ALARM indicators are

illuminated. In addition, the ALARM relay is activated.

3) Wait for up to 30 minutes, and note that the ALARM

indicator turns off and the LOCK indicator turns on.
The ALARM relay is reset. The outputs are ready to
use.

Note: The factory default for ALARM operation is

“warning mode,” which is as described above (non­latching operation). The user may change operation to
“critical mode” as described in the next chapter. In
critical mode, the ALARM is latching, and must be reset
by the user over the RS232 port, by issuing the RESET
ALARM command, as described in the next chapter.

2.3 TURN-OFF PROCEDURE AND RESTARTING

1) Unplug the ac power connector from the rear panel.

This is the turn-off device.

2) To restart the instrument, re-connect the ac power

connector on the rear panel and wait for the LOCK
indicator to illuminate.

2.4 CONTROL AND MONITORING VIA THE RS232 PORT
The DATUM Cesium Frequency Standard may be
controlled or monitored via the RS232 ports. The software
interface uses a proprietary interface, described in Section 3.

2.5 1 PPS OPERATION
The 1 PPS output remains off until the unit locks. The unit
will provide a stable output as long as the unit remains
LOCKed.

To synchronize the 1 PPS output to an external source,
connect the source to the SYNC input and issue a PPS
SYNC ENABLE command as described in Section 3.

2-1

DATUM Cesium Frequency Standard SECTION 2

OPERATION

SECTION 2

OPERATION

DATUM Cesium Frequency Standard SECTION 2

OPERATION

TABLE OF CONTENTS

SECTION 2. OPERATION.......................................................................................................................... 2-1

2.1 INTRODUCTION.......................................................................................................................2-1

2.2 TURN-ON PROCEDURE.......................................................................................................... 2-1

2.3 TURN-OFF AND RESTARTING..............................................................................................2-1

2.4 CONTROL AND MONITORING VIA THE RS232 PORTS ................................................... 2-1

Datum Cesium Frequency Standard SECTION 3
RS232 INTERFACE

SECTION 3. RS232 INTERFACE

3.1 INTRODUCTION
This section describes the protocol for the RS232 Interface
and includes general communication parameters as well as
the command list.

3.2 GENERAL PARAMETERS
The default for the RS232 interface parameters are 9600
baud, 7 bits, odd parity, 2 stop bits.

3.3 OPERATING NOTES
Only two operating functions require the use of the RS232
interface: W22—Arm 1 PPS Sync Circuit and A18--Set
Restart Fault Level. The other commands are for
performance monitoring, diagnostic and factory use.

3.4 CESIUM COMMAND REFERENCE
Commands are sent to the system via RS232. The Cesium
III command set is backwards compatible with the
5045A/4201A command set. Several new commands
support the new capabilities of the Cesium III system.

General format: <STX><Function Code>_<IDENT>_<DATA><ETX>

Element Description

STX 002
_ Space character
[<DATA>] Data: this string is of variable length
<IDENT> 5 character unit identification number - * Note 1
<Function Code> Function code, see table
ETX 003
All entries in the data field are left justified, and the remainder (if any) of the
Data field must be filled in, to round it up to 9 characters in length

Command Description Data Field
Standard
functions

W00 Reset alarms No data required
W01 Set frequency offset (permanent,

Sign plus 6 digits
value is saved in NVRAM and
restored on power up). The offset is
in parts e-15

3-1

Datum Cesium Frequency Standard SECTION 3
RS232 INTERFACE

Command Description Data Field
Standard
functions

W02 Unused
W03 Time updating (advance or retard 10

Sign plus 4 digits
MHz phase by n nanosecond)

W04 Reset time updating (halts a time

No data required
updating operation.

W05 Disable the C-Field Servo No data required
W06 Enable the C-Field Servo No data required
W07 Unused
W08 Obsolete… Sets the 5045 compatible

day of year and time

9 digits:

3 digit day

2 digit hour

2 digit minute

2 digit second

W09 not used
W10 Set the servo filter order and time

constant. The servo filter order is
fixed at 1 in the Cesium III line of
products

6 characters:

1 filter order

2 space

3-6 floating point

number

W11 Set frequency offset (not saved in

Sign plus 6 digits
NVRAM). The offset is in parts e-15

W12 Mute signals No data required
W13 Un-mute signals No data required
W14 Mute override No data required
W17 Alarm relay cut off No data required
W18 Clear event log No data required

W22 Arm 1pps sync circuit. Issue this command

after connecting a 1pps source to the Cesium
III. The sync will remain armed for 3
seconds.

No data required

3-2

Datum Cesium Frequency Standard SECTION 3
RS232 INTERFACE

Special
functions

T*1 Obsolete (Remote control off)
T*2 Obsolete (Remote control on)

No data required

No data required

D*1 Return Variables (250 characters) No data required
D*2 Return Constants (129 characters) No data required
D*3 Retrieve Event Log No data required
D*4 Report Extended status…Alternate

No data required
report of internal system status, using
higher resolution numbers and
comma separated values.

D*5 Report the contents of the internal

No data required
non volatile memory (NVRAM)

S01 Set operating mode to clock servo

only. This disables the microwave
servo, the c-field servo, and the gain

0 = return to normal

clock operation

1 = servo only mode
servo.

S02 Disable/Enable VCXO servo 0 = off

1 = on

S03 Disable/Enable C-Field servo 0 = off

1 = on

S04 Disable/Enable Microwave power

servo

0 = off

1 = on

S05 Disable/Enable the gain servo 0 = off

1 = on

S06 Set VCXO Control Voltage A floating point

number between 0 and

5.8
S07 Set Numeric and DAC gain values DAC, numeric
S08 Set C-Field Control Voltage A signed floating point

number between –2.5
and +2.5

S09 Set microwave power Control

Voltage

A floating point
number between 0 and
5

3-3

Datum Cesium Frequency Standard SECTION 3
RS232 INTERFACE

Console
functions

C01 Set unit number. 5 digits
C02 Memorize nominals No data required
C03 Return software version No data required
C04 (obsolete)Set language

(English/French/German)

1 digit
1=english
2=french
3=german

C05 Set serial port parameters Baud, data, parity, stop

bits

C06 Set Eudics Message 9 characters

New
functions

A01 Set Test Mode 1… This performs

A02 Set Test Mode 2… This sets the dds

A03 Set Test Mode 3… Program the Gain

internal diagnostics

to one of the 9 interrogation
frequencies

DAC to a fixed value

0 = off
1 = do test
0= off
1–9=select DDS
frequency
0 = off
1-256 =

A04 Set the dds to A 48 bit dds control word

(hex)
Setting the data to ‘off’
will restart the clock….

A05 Sweep the dds. 48bit start, 48 bit delta f, 4

digit number of steps
A06 Set Date (year, month, day) Yyyymmdd
A07 Set Time (hour, minute, second) Hhmmss
A08 Return Date and Time
A09 Set Daylight savings mode 1=on

2=off
A10 Return Daylight Savings mode
A11 Leap Second insertion at next interval 0=Enabled 1=Disabled
A12 Set power on hours… this allows you

integer

to override the permanent record of
power on hours

A13 Set Expected tube service life (in

3 digits

months)
A14 Return power on hours No data required
A15 Set Response mode 0 = normal

1 = verbose

A16 Reset NVRAM to default values No data required

3-4

Datum Cesium Frequency Standard SECTION 3
RS232 INTERFACE

A17 Set Manufacturing Date Mm, dd, yy
A18 Set Restart Fault Level 1 = restart is critical fault

0 = restart is not a critical
fault

Data returned by the “Return Variables” command

Variable Field Example
STX CR LF 1-3
Unit serial number 4-10 ID00025
Day Meter 12-14 537
Time (hour minute second) 16-25 16h13mn22s
First or second order servo loop 27 2
Operating mode 29-31 R+Z
Alarms state

33-54 ALM:00(00,00,00,00,00)
* Note 2
C-Field adjustment 55-59 C +015
Frequency fine tuning 61-68 F –006
24v power supply 70-76 +24.8V
Filtering time constant (seconds) 78-83 Ct05.0
CR LF 84-85
Clock servo voltage difference 86-90 R–019
Clock pedestal servo voltage

91-98 RR +0045
difference
Zeeman servo voltage difference 99-103 Z* + 0008
Zeeman pedestal servo voltage

104-111 RZ–0004
difference
Oscillator servo output voltage 112-118 AR–0029
Clock peak to background level

119-124 PR2506
difference
Zeeman servo output voltage 125-131 AZ+0007
Zeeman peak to background level

132-137 PZ1765
difference
Preamplifier DC level servo output

138-144 AO + 0690
voltage
Numerical gain 145-151 GN*1.53
Clock (ramsey) peak symmetry check 152-158 LA–0005
Microwave power servo control

159-165 Pu–2875
voltage
CR LF 166-167
+5V power supply 168-173 +5.08V
Internal case temperature 175-180 T+27.7
+15.5V power supply 182-187 +15.1V
–15.5v power supply 189-194 –16.2V

3-5

Datum Cesium Frequency Standard SECTION 3
RS232 INTERFACE

Quartz oscillator cold/warm 196-198 Olc
Cesium oven supply voltage 200-205 F0008.0
Mass spectrometer voltage 207-212 VS18.9
Cesium beam tube Ionizer voltage 214-219 VF1.5
C-Field coil current 221-226 IC14
HTEM control voltage 228-233 HT10.6
Ion Pump current 235-239 IP025
Allan deviation of clock servo

241-247 +137 mV
voltage over 30 seconds
CR LF ETX 248-250

Data returned by the “Return Constants” command

Variable Field Example
STX CR LF 1–3
Unit serial number 4–10 ID00025
Day Meter 12–14 006
Time (hour minute second) 16–24 04h54mn32s
Spectrometer voltage nominal 26–33 Vs 14.0V
Tube ionizer voltage nominal 35–44 Vf 1.07V
Gain DAC 44–51 GDAC 008
F(t°) correction model at –15°C 48–54 –15:+10
F(t°) correction model at +15°C 54–59 +15:+00
F(t°) correction model at +45°C 61–67 +45:–03
F(t°) correction model at +75°C 69–75 +75:+04
CR LF 84–85

12.6MHz level nominal (J1 max) 86–92 Pi+0345
Zeeman offset (Assymetry

94–100 Oz–0045
compensation)
Auxiliary output signal frequency 102–112 Fo:05.0MHz
Console mode language 114–119 CDU: GB
Comments 121–134 TXT(1234567890)
Eudics program version 136–138 370
Eudics program revision 140–142 1.8
CR LF ETX 143–145

3-6

Datum Cesium Frequency Standard SECTION 3
RS232 INTERFACE

3.5 EVENT LOG
A portion of the non-volatile memory in the system is
reserved for storage of event records. Event records consist
of a time stamp and an event mask. Any change in the
system status is recorded as a new event in the log. The
event log can be cleared by an external command. Because
the CSIII lacks a battery backed up real time clock, the
Event log stores two distinct time stamps. The first is a 6
byte calendar date, the second is a 32 bit value representing
the total system power on hours.

3.6 TROUBLESHOOTING
If the ALARM activates and remains lit indicating a failure
of the 4310, call Datum Customer Service for instructions.

Table 3-6 lists the two-digit numeric fault codes and gives
description of each. If any of the following fault codes are
observed, refer to the comment in the Comments column.
If unable to resolve the cause of the fault, contact Datum
Customer Service for further instructions.

Note 1 The five zero’s are the “five digit unit identification number”. One can use the last five digits of

the actual serial number (marked on each unit), or one can use five zero’s as in the example
shown above.

Note 2 The data returned by the “Return Variables” command, in fields 33 thru 54 are the Alarms and

the four possible system states. By reading these, one can know the state of the instrument. The
data is presented as follows:
ALM:ss(00,00,00,00,00)

where ss indicates the system state

00 operation
01 warm up
10 minor fault
11 major fault

The digits enclosed in parentheses are fault codes. See the System Fault Codes Table below.

3-7

Datum Cesium Frequency Standard SECTION 3
RS232 INTERFACE

Table 3-6, Fault Messages

Fault Code Description Comment

01 Clock Peak to Background <1320 or >3080 mV

02 Clock Pedestal Symmetry >50 mV

03 Zeeman Pedestal

Symmetry

04 Mass Spectrometer >5% or nominal (±0.7 V)

05 C-field Current <16.0 or >22.0 V

06 Electron Multiplier Supply <7.0 or >13 V

07 ADC

08 VCXO Control Voltage <10% or >90% (±4000 mV)

09 Case Temperature >80°C

10 Not used

11 Not used

12 +5 V Supply <4.75 or >5.25 V

13 +15 V Supply <13.5 or >16.5 V

14 -15 V Supply >-13.5 or <-16.5 V

15 Not used

16 Unit Restarted

17 Module configuration not

set

>160 mV

18 Digital Gain at lower limit = 1

80 Software Failure

81 Event Log Invalid

F1 Cesium Oven Warm-Up >10.0 V (after warm-up)

F2 OCXO Oven Warm-Up >2.5 V after initial warm-up

F3 Ionizer Filament >±0.16 V of nominal

F4 Ion Pump Current >175 uA

F5 +24 V Supply <17 or >24 V

3-8

Datum Cesium Frequency Standard SECTION 3
RS232 INTERFACE

SECTION 3

RS232 INTERFACE

Datum Cesium Frequency Standard SECTION 3
RS232 INTERFACE

TABLE OF CONTENTS

SECTION RS232 INTERFACE........................................................................................................ 3-1

3.1 INTRODUCTION .......................................................................................................... 3-1

3.2 GENERAL PARAMETERS .......................................................................................... 3-1

3.3 OPERATING NOTES .................................................................................................... 3-1

3.4 CESIUM COMMAND REFERENCE ........................................................................... 3-1

3.5 EVENT LOG ..................................................................................................................3-7

3.6 TROUBLESHOOTING.................................................................................................. 3-7