Novus NR2310D-RO User manual

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NR2310D-RO
10 Channel, Low Noise, Rubidium Frequency Reference with
RS232, Display and optional Ethernet-SNMP
All information provided herein is the proprietary property of Novus Power Products
LLC. The information included may be reproduced without the permission or prior
approval of Novus Power Products LLC for the purpose of operating the equipment.

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Contents
Contents ...........................................................................................................................2
Safety................................................................................................................................3
Mounting ..........................................................................................................................4
Summary...........................................................................................................................5
The Time Base..............................................................................................................6
External PPS Locking ..................................................................................................8
The unit may be configured to lock to an external PPS signal. The signal must
conform to 3.3 V CMOS into a 1000 Ohm load. Rise time must be less than 10ns and
the pulse width must be greater than 10 ms.....................................................................8
PPS ...................................................................................................................................8
Base Unit Block Diagram...............................................................................................10
Phase Noise Performance...............................................................................................11
Controls and indicators...................................................................................................11
Channel Status- Front panel LED’s ...........................................................................12
Oven- LED front Panel...............................................................................................12
Digital Display (Optional)..........................................................................................12
RS232 NMEA / Alert –DB9 Male (Optional) .........................................................12
Rear Panel - Outputs.......................................................................................................13
Channel 1 through 10 output connectors –BNC or SMA .........................................14
Latch Channel Values ................................................................................................16
PPS –SMA (with GPS locking option) .....................................................................20
Alert –BNC-SMA......................................................................................................20
Power In......................................................................................................................20
Functional Description (Base NR2310D-RO) ...............................................................21
Outputs .......................................................................................................................21
Built-in Test....................................................................................................................21
Power Supplies...........................................................................................................21
Redundant power........................................................................................................22
Specifications .................................................................................................................23
Technical Specifications.............................................................................................23
Environmental and Mechanical..................................................................................24
Appendix C Novus Status and Control Strings..............................................................25
LIMITED HARDWARE WARRANTY .......................................................................26

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Safety
This product has been designed and manufactured to recognized safety standards and
rules. The product is a sophisticated electronic instrument that should be installed and
operated by highly trained professionals.
Installation of this equipment should comply with all local electrical codes.
Utilization of this equipment in a manner inconsistent with the operating instructions
can be dangerous.
There are no user serviceable parts within the unit. Removal of the cover to access
interior parts will expose the user to dangerous voltages.
The unit may be powered from more than one power source. Care must be taken to be
certain all power sources are removed before installation or during removal of the
equipment.
The unit must be operated with a secure earth ground to the chassis. The electrical path
for earth ground is through the power connector. The power switching device that
controls power to the equipment must never interrupt the chassis ground connection.
The equipment contains complex electronic components that can be damaged by
electrostatic discharge. Observe all recognize standards for the handling of complex
electronic devices to avoid high voltage discharge to the equipment. Be certain the
equipment chassis and operator are at equipotential before handling the equipment.

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Mounting
The equipment is meant to operate in a horizontal - top up configuration.
The equipment is meant to mounted into a 19 inch standard NEMA cabinet. The unit
occupies a single “1ru”. Mounting spaces above and below the equipment may be used
as required.
Please observe the operating temperature range for the equipment. If mounted into a
closed rack, be certain that the total heat load in the cabinet does result in an interior
operating temperature that exceeds the equipment maximum rated temperature.
If cooling must be used, care should be given to prevent cooling mechanical vibration
from the coupling into the equipment. Mechanical shock and vibration may introduce
noise into the electronic signals inside the equipment that may degrade the
performance of the equipment. For applications where there is significant shock and
vibration, Novus offers equipment with interior mechanical design features to
minimize the effects of vibration and shock on the equipment performance.

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Summary
The NR2310D-RO is a high performance 10 channel, 10 MHz, Rubidium frequency
reference. The core time base is a Rubidium source. The Rubidium source is followed
by a low noise OCXO locked to the Rubidium. The ten channels provide a 13 dBm
sine output that is transient, and fault protected. The unit also provides a single channel
simulated PPS output and a RS232 port. The RS232 port provides NMEA 0183 data as
well as proprietary data streams for instrument status and control. The unit features a
front panel display for equipment status and control. An optional ethernet port allows
remote access and control via SNMP. There are four levels of optional reference
control for improved Allan Deviation performance and PPS accuracy and jitter. The

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platform also supports redundant power sources AC or DC. The unit may optionally be
configured to lock to an external PPS signal.
The Time Base
The heart of the system is the reference. Novus offers OCXO and Rubidium
based references. Because of the relatively poor phase noise performance of
Rubidium, many of our customers select a Rubidium with a cleanup OCXO to
achieve high stability and low phase noise. Following is a plot of the phase
noise of a Rubidium reference and a Rubidium reference followed by a clean-
up OCXO.
Our Rubidium references offer a stability of < ±5E-11/month compared to a
typical OCXO ±50 ppb/year. The Rubidium source consists of a
voltagecontrolled crystal oscillator (VCXO) which is locked to a highly stable
atomic transition in the ground state of the 85Rb isotope.
Novus uses several vendors for the OCXO. The OCXO selected is based on
required phase noise, stability, and cost. There are other secondary
considerations such as size, power consumption, etc.

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In addition to standard OCXO devices, Novus also uses double oven OCXOs
as an alternative to a single oven OCXO. As can be imagined, a double oven
OCXO offers improved temperature stability and is frequently a lower cost
alternative to a Rubidium source.
A TCXO reference might be considered for a low-cost application. It offers an
aging stability that is on the order of ±1000 ppb/year. Phase noise is typically
not as good as that of an OCXO - but it is lower cost and consumes much less
power.
Stability/Year Temperature Adev@1 sec
ppb ppb/ 0 to 70C Seconds
TCXO <+-1000 <+-1000 1.00E-09
OCXO <+-50 <+-10 1.00E-10
Double OCXO <+-10 <+-0.2 5.00E-12
Rubidium <+-1 <+-0.1 5.00E-11
Timing Sources Comparison

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External PPS Locking
The unit may be configured to lock to an external PPS signal. The signal must
conform to 3.3 V CMOS into a 1000 Ohm load. Rise time must be less than
10ns and the pulse width must be greater than 10 ms.
PPS
The simulated PPS signal is available on a rear panel sma connector. There
are numerous attributes that can be controlled via the serial port or were
selected at the time the instrument was ordered.
Pulse Alignment (option)
Pulse Alignment Screen
Once the unit has achieved lock, and is in stable mode, the rising edge of the PPS can
be moved relative to the sine wave in 5ns increments. This allows for the PPS to align
to 20 positions in a complete cycle. To adjust the position of the PPS, allow the unit to
enter stable mode, and navigate to the Pulse Alignment screen with the NEXT button.
When unit reaches stable mode, the position of the PPS relative to the sine output will
be read from the reference module, and displayed as n/19, representing the positions 0-
19.
The position of the pulse, relative to the sine wave should be verified on an
oscilloscope during adjustment. The value on the screen does not necessarily indicate
fraction of cycle distance from rising edge. When adjusted, the pulse will advance 5ns
to the position of the sine output.
In order to increment the position of the PPS, press the SELECT button. The value of
the position, as read from the reference module, will increment. The read value will
indicate “Unlocked” until the unit has stabilized at the new set value.

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Wait 15 seconds before incrementing between steps. If the pulse moves excessively,
the unit may come out of stable mode. Simply wait for the unit to achieve stable mode
again before moving.
To save changes to non-volatile memory, go to “Save Configuration” screen, and press
SELECT.
Pulse Alignment over Serial Port
To set the PPS offset via the serial port, enter the value (0 to 19) with the $PSALN
command:
Example: $PSALN=2<cr><lf> Sets the PPS alignment to position 2 relative to
the sine.
To query the position of the PPS, enter $PSALN<cr><lf> with no parameters
following.
To save changes to non-volatile memory, enter “SAVEFLASH<cr><lf>”.

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Base Unit Block Diagram
There is built-in test circuitry throughout the design. Power supplies, signal
present are monitored and are used to drive a status relay as well as indicators
on the front panel and optional serial and Internet communications paths.
The unit display allows local monitoring and remote monitoring via an RS232
serial link or ethernet port.
The ten-channel amplifier is designed for ultra-low noise to preserve the low
noise performance of the reference. This multi-channel design frequently
results in the elimination of a system distribution amplifier and consequently

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lower system noise performance while reducing the system cost and rack
space requirement.
Phase Noise Performance
Typical phase noise performance is indicated below. The phase noise performance is
dominated by the OCXO and the noise contribution of the ten-channel distribution
amplifier. The amplifier was designed to minimize phase noise contribution through
the use of low noise power sources and high-performance amplifiers. The OCXO
performance is determined by the device used and there are a range of options
available. Contact the factory for performance levels available.
Typical phase noise performance
Controls and indicators

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Channel Status- Front panel LED’s
For the base unit, three LEDs indicate status of the unit, monitoring for channel
faults, Oven Status (and GPS Lock Status), and System Status. The optional
Display provides the user with GPS lock information, time, and Channel Status
as detailed in the screens that follow.
There are a number of critical circuits in the unit. These are monitored and a
failure of any of these will initiate an Alert condition. The ALERT led on the
front panel will go from green to flashing red and the Alert relay will open. The
alert relay is accessed by a BNC connector on the rear panel. The normal
operating state is the relay will be closed.
Oven- LED front Panel
Green indicates that the Oven is operational, and that GPS lock has been
acquired for NR2310 with GPS Locked option. A red color indicates that the
oven associated with the OCVCXO has failed.
Since the NR2310-ROG is a GPS locked reference, during power-on, the
OVEN LED will flash during tracking, and until a GPS Lock status is achieved.
This can take up to 30 minutes –typically < 10 minutes.
Digital Display (Optional)
The NR2310D-OG OLED Display gives a number of useful indicators about the
frequency reference. Each menu available at the display can be reached by
pressing NEXT to advance through the available menus.
RS232 NMEA / Alert –DB9 Male (Optional)
RS232 Communication at 38400 baud. Flow Control: None.

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Alert: Pins 8 and 9 are closed across a relay under normal operation. This
allows the user to place any positive voltage up to 20VDC as a logic value
across the relay connections. The relay opens in any of the following alert
conditions: GNSS Lock is lost, OCXO Lock is lost, OCXO oven failure, or
power failure. This Alert Option is not available with the Rubidium .
DB9 Male Connections:
Pin 2: Tx
Pin 3: Rx
Pin 5: GND
Pin 8: Alert +
Pin 9: Alert –
Rear Panel - Outputs

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Channel 1 through 10 output connectors –BNC or SMA
The ten BNC or SMA connectors 10 MHz sine @ 50 Ohm load.
Output Channel Status Monitoring
The channel status is determined by reading the actual RMS value in volts on
the output of each stage. This value is compared to a threshold limit that is set
by the user as a percentage variation from a saved value. The default variation
value is set at ±55% from the current state of the amplifier, and is user-
programmable from ±10% to ±60%.

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To optimize this feature, the range of acceptable channel amplitude can be
narrowed around a connected balanced line, so that a channel status below
the Alert Threshold indicates a shorted line, while a channel status above the
Alert Threshold window indicates a potential disconnected cable.
The threshold value at which a channel alert is triggered can be programmed
on the Alert Threshold screen or programmed via the RS232 port. Once set,

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the unit would continue to monitor each channel and a deviation beyond the
set limits would be reported as a failure on the front panel and via RS232.
The channel status feature can quickly detect a cabling failure. Any change in
the load impedance will change the output voltage with respect to the divider
formed by the output impedance of the amplifier and the load impedance.
Failing cables and connectors can be detected early.
On the Output Channels screen, the current threshold limits are displayed in
addition to the actual measured value. These values reflect the percentage
threshold defined in the Alert Threshold settings. If the output value is too low
to give a valid reading, the display will read “LOW.” The status is displayed on
the front panel and is accessible over the RS232 serial bus via DB9.
If the channel output exceeds either the high or low threshold, the output value
will illuminate in red, and the STATUS LED will blink red.
Latch Channel Values
The Latch Channel Values Screen allows the user to save the current channel
output values for use as the reference value for alert settings. A channel alert
is triggered when a channel output voltage exceeds or falls below a
percentage of the reference value. This reference value is 1.10Vrms as a
default, but can be set by the user.
1. Turn on the NR230D-R/O or NR2310D-R/O/G and allow to warm up at least
30 minutes prior to starting this procedure.
2. Using the “NEXT” button, navigate to the “Latch Channels” screen.

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3. Press the “SELECT” button to set the High and Low limits based upon the
channel value.
4. Press the “SELECT” button again to overwrite the settings.
5. Press “NEXT” to get the “Save Configuration” menu.

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6. Press the “SELECT” button to Save the Configuration. .
“
7. Press “Select” to store the configuration into memory.
The RS232 serial port allows for setting an individual channel’s reference
voltage with the $SET command. The user can also use the Latch Channel
Values to take a snapshot of all current outputs and use these as the reference
values.
The alert threshold can be optimized so that a channel short or an impedance
change will cause an Alert.

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Example:
The output of channel 1 is connected to a high impedance input and
reports 1.25Vrms at the output. The output of channel 2 is connected to
a 50ohm terminated input and reports 0.90Vrms at the output.
Alert threshold is set to +/-20%.
The current state is saved in the Save Configuration screen.
The Channel 1 alert will report when:
-The Channel 1 output is higher than 1.50Vrms
-The Channel 1 output is lower than 1.00Vrms
The Channel 2 Alert will report when:
-The Channel 2 output is higher than 1.08Vrms
-The Channel 2 output is lower than 0.72Vrms
To set channel values vis the serial port:
Setting Command Response Description
$SET<nn>=n.nn
$SET01=01.00
$SET02=01.00
$SET03=01.00
.
.
.
$SET15=01.00
$SET<nn>=nn.nn
Set or query the Reference Voltage for a perticular
channel with respect to the active input. Use in
combination with the Channel Fault Threshold Factor to
define Alert on an individual Channel. Reference
Voltages are set with respect to the active input,
allowing for variation in amplitude between Input A
and Input B.
Example: Set Channel 4 to Alert if it is beyond
+/-20% of 0.90Vrms when relayed to Input A:
$SET04=0.90<CR><LF>
$FLTTHR=0.20<CR><LF>
( To set all channel Reference values to their current
average amplitude, use the Latch Average Channel
Values command.)
SET INDIVIDUAL
CHANNEL
REFERENCE
VOLTAGE

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PPS –SMA (with GPS locking option)
PPS output: 5V, TTL, short and transient protected. The PPS has a pulse
width of 100µs and an accuracy of 20 ns rms. The PPS is programmable in 1
usec steps
Alert –BNC-SMA
Connects to the status relay. Contacts rated at 20 VDC/VAC, 0.5 amps.
Contacts are closed during normal operation. Alert status will cause relay to
open. The BNC option eliminates one output port if selected.
Power In
Primary power input. The unit operates from 50 or 60 Hz, 88 to 250 VAC. The
unit does automatic sensing of the input voltage and there are no actions that
need to be taken to operate across the defined AC voltage range. Connector
style IEC 320-C14. The is available with a DC power option that can range
from -60 to +60 VDC in three ranges. The DC supply can be the primary or
secondary back-up to the AC.