Novus Time-Master NT9400 User manual

Users manual
NT9400
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TimeꞏMaster
NT9400/NR9400/9400
All information provided herein is the proprietary property of Novus Power Products
L.L.C. The information included may be reproduced without the permission of Novus
Power Products L.L.C. without prior approval for purpose of operating the equipment.

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Contents
1.0 Overview................................................................................................................................ 3
2.0 Key Functional Elements ....................................................................................................... 6
2.1 GNSS Receiver ................................................................................................................... 7
2.3 Rubidium Clock.................................................................................................................. 9
2.4 Power............................................................................................................................... 10
3.0 Functional Controls and Indicators ..................................................................................... 12
3.1 Acquire/Lock.................................................................................................................... 13
3.2 Battery............................................................................................................................. 14
3.4 NTP time server option.................................................................................................... 16
3.5 NT9400 Display and Menu Navigation............................................................................ 17
4.0 Frequency Reference Output .............................................................................................. 37
Offset Frequency (Hz) Typical (dBc / Hz) ............................................................................ 37
5.0 IRIG-B Output ...................................................................................................................... 38
6.0 Data Outputs ....................................................................................................................... 39
6.1 USB Port........................................................................................................................... 39
6.2 RS232............................................................................................................................... 40
6.3 RJ45 Ethernet Port........................................................................................................... 41
7.0 BNC –Rear Panel................................................................................................................. 42
8.0 Quick Start Guide................................................................................................................. 44
8.1 Differential Measurements (Compare Mode)................................................................. 46
9.0 Post Use............................................................................................................................... 47
10.0 Event.................................................................................................................................. 48
10.1 Event String (RS232 and USB)........................................................................................ 49
11.1 Programming Guide (RS232 Port) ..................................................................................... 50
11.1 $GPNVS String Definitions............................................................................................. 51
12.0 Packaging........................................................................................................................... 57
13.0 Accessories ........................................................................................................................ 58
14.0 NTP Time Server (option) .............................................................................................. 59
15.0 Technical Specifications..................................................................................................... 61

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16.0 LIMITED HARDWARE WARRANTY ................................................................................. 63
1.0 Overview
The NT9400 is a portable time source for GNSS and GNSS denied environments
with the following capabilities:
●10 MHz output locked to GNSS or atomic holdover.
●NMEA simulator that continues to provide NMEA data even after GNSS loss.
●PPS output that is GNSS derived with atomic holdover.
●Battery powered to provide > 6 hours field use.
●Optional NTP time server with atomic holdover
●Optional IRIG-B output, modulated or unmodulated
●Built-in drift estimation and measurement.
●Rugged water-resistant case.
●Pairs of events may be captured as close as 1µS with A/B inputs
When locked to the GNSS, the NT9400 operates as a standard GNSS locked
frequency reference and PPS source with an accuracy 20 nS. While locked to
the GNSS, the Rubidium internal reference is continually being disciplined in
frequency and its internal PPS is aligned to UTC PPS within <200 nS. If GNSS is
lost, the unit uses the disciplined Rubidium as the master time reference. The
PPS remains aligned to UTC PPS with a drift rate of <40µS/day (procedure
allows for better drift performance).
The deviation from PPS after an extended period of time of GNSS loss is
presented in the drift counter display during a GNSS and Rb Lock state. This
same display is used for differential measurements of an external PPS signal in a
GNSS denied environment. If configured for differential measurements, an
external PPS signal can be applied and the unit will measure the time difference
between the leading edge of the internal-atomically stabilized PPS and the
external PPS. Two event inputs can measure difference between two rising edge
pulses.

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NMEA and NTP data continues to be streamed using the Rubidium based PPS
to increment internal counters. Position is reported as the last best known
position.
Time and position stamping are available through the event function. A
programmable rising/falling edge causes the current time and position to be
recorded. This data is stored in non-volatile memory and can be read via the
local display. If the Ethernet option is available, the unit can be configured to
transmit an email with the event data. The event data can also be downloaded
as a file to be manipulated off-line. Events are captured and stored to a
resolution of 100 nS.
Up to 512 events can be stored in the memory. Events can be as close in
occurrence as 1 µS. Events are captured and stored to a resolution of 1µS.
The external PPS monitor allows for the measurement and monitoring of an
external PPS source. The external PPS is measured against the internal PPS
that is GNSS derived with atomic holdover. The difference in time between the
internal and external is displayed on the UTC drift display. Also, an alert can be
set so that if the drift exceeds a certain bounds, an alert will be generated that
will be displayed locally or an email can be programmed to be sent.
Multiple units may be synchronized thru the (optional) Aux connector by applying
a PPS signal from a Master source to multiple units. This allows multiple high
speed events to be captured time synchronized without having the expense of
multiple atomic references.
Battery life is a function of configuration and use. The NT9400, in its base
configuration, can achieve well over six hours of battery life. As you add features
such as NTP, the battery life can fall to approximately six hours. The battery
recharges in approximately six hours. Charge status and battery remaining
capacity indicated on the front panel. The battery is accessible and easily
replaced through a removable panel.
Power is provided by either a power adapter (PA0008) or nominal 12Vdc. The
PA0008 operates from 90 to 260 Vac and has a splash proof housing. There is a
storage compartment for the adapter in the unit when not in use. The battery is
being charged when power is present in the DC input port.

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The NT9400 case is a high impact injection molded case. The lid seals with
gaskets to provide weather resistance and the timing platform is shock protected
from the case with isolators.
A magnetic mount GNSS antenna is provided which is stored in the unit. It has a
28 dB LNA to provide gain in low signal environments. The antenna can be
easily removed and a different antenna/source can be used. Antenna status is
presented on the front panel (open/fault).
The following output options available:
NMEA - RS232, USB 38400 Baud
NTP Time Code - RJ45
10 MHz sine wave - BNC
PPS - BNC 3.3 Volt CMOS
Auxiliary Output - BNC (other frequencies) (Event-In)
IRIG-B (modulated 1kHz or DCLS)
Event Inputs (2): A/B Dual Event Input

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2.0 Key Functional Elements
LCD- Control
Processor
NTP Time Server
NMEA Time Server
GNSS Receiver
Rubidium Clock
RJ45-Ethernet
RS232 NMEA
USB NMEA
Battery
Charger
Vdc Input
12
to 264 Vac
90
Adapter
Antenna
GNSS
YES
NO
Mhz Sine
10
Frequency
Synthesizer
Secondary
Frequency
Event

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2.1 GNSS Receiver
The receiver and companion elements generate the GNSS sine wave, PPS and
NMEA serial link. The serial link conforms to NMEA 0183 protocol. The GNSS
receiver leverages 12,288 correlators in the baseband processor for low signal
acquisition and tracking. The unit comes with a GNSS antenna with a built- in 28
dB LNA. The local antenna may be detached, and an external antenna used.
The receiver needs at least four satellite vehicles (SV’s) visible to obtain an
accurate 3-D position fix. When travelling in a valley, or built-up area, or under
heavy tree cover, you will experience difficulty acquiring and maintaining a
coherent satellite lock. Complete satellite lock may be lost, or only enough
satellites (3) tracked to be able to compute a 2-D position fix, or a poor 3D fix due
to insufficient satellite geometry (i.e. poor DOP). It may not be possible to update
a position fix inside a building or beneath a bridge. The receiver can operate in
2D mode if it goes down to seeing only 3 satellites by assuming its height
remains constant. But this assumption can lead to very large errors, especially
when a change in height does occur. A 2-D position fix is not considered a good
or accurate fix; it is simply “better than nothing”.
The receiver’s antenna must have a clear view of the sky to acquire satellite lock.
Remember, it is the location of the antenna that will be given as the position fix. If
the antenna is mounted on a vehicle, survey pole, or backpack, allowance for
this must be made when using the solution.
To measure the range from the satellite to the receiver, two criteria are required:
signal transmission time and signal reception time. All GNSSGNSS satellites
have several atomic clocks that keep precise time and are used to time-tag the
message (i.e. code the transmission time onto the signal) and to control the
transmission sequence of the coded signal. The receiver has an internal clock to
precisely identify the arrival time of the signal. Transit speed of the signal is a
known constant (the speed of light), therefore: time x speed of light = distance.
Once the receiver calculates the range to a satellite, it knows that it lies
somewhere on an imaginary sphere whose radius is equal to this range. If a
second satellite is then found, a second sphere can again be calculated from this

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range information. The receiver will now know that it lies somewhere on the circle
of points produced where these two spheres intersect.
When a third satellite is detected and a range determined, a third sphere
intersects the area formed by the other two. This intersection occurs at just two
points. A fourth satellite is then used to synchronize the receiver clock to the
satellite clocks.
In practice, just four satellite measurements are sufficient for the receiver to
determine a position, as one of the two points will be totally unreasonable
(possibly many kilometers out into space). This assumes the satellite and
receiver timing to be identical. In reality, when the receiver compares the
incoming signal with its own internal copy of the code and clock, the two will no
longer be synchronized. Timing error in the satellite clocks, the receiver, and
other anomalies mean that the measurement of the signal transit time is in error.
This, effectively, is a constant for all satellites since each measurement is made
simultaneously on parallel tracking channels. Because of this, the resulting
ranges calculated are known as “pseudo-ranges”.
To overcome these errors, the receiver then matches or “skews” its own code to
become synchronous with the satellite signal. This is repeated for all satellites in
turn, thus measuring the relative transit times of individual signals. By accurately
knowing all satellite positions and measuring the signal transit times, the user’s
position can be accurately determined.

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2.3 Rubidium Clock
The Rubidium reference employs a coherent trapping (CPT) technique to
interrogate an atomic frequency. A laser illuminates’ atoms in a resonant cell with
polarized radiation. The laser excitation significantly reduced Rb power
consumption compared to a conventional Rb source plasma cell. A microwave
synthesizer provides the energy for the two sub-bands. Light passing through the
resonant cell is modulated at resonance and the intensity of the light
transmissibility is used to control the microwave frequency. Locked to the atomic
frequency, the microwave frequency is the basis for the 10 MHz generated. The
stability of the source is less than 1 ppb/year which is almost two orders of
magnitude better than a typical OCXO. It is successfully used in applications
where long-term stability is a necessity, but GNSS may not be accessible.
During GNSS lock, the Rb atomic clock output frequency of 10 MHz is
synchronized to the GNSS PPS. The 10 MHz clock drives a counter to generate
a PPS signal. That counter is initially synchronized to the GNSS PPS to within
200 ns. During the discipline period, the Rubidium generated PPS will then
follow the GNSS PPS until “Discipline Good” status is achieved. During this
discipline period, the Rubidium status will show “Discipline Wait” while the
Rubidium source adjusts its frequency output.
Once the full synchronization and discipline has taken place, the PPS accuracy is
dictated by the atomic clock. Below is an estimate of the drift performance of the
PPS when the NT9400 is no longer connected to GNSS.

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2.4 Power
The primary battery pack is a two cell Lithium ion that can be easily replaced
through an access panel.
The internal charger operates either from an external 12Vdc source (11 to
15Vdc) or a splash-proof charger that operates from 90 to 264Vac.
The charger is housed within the unit. The NT9400 is fully functional during
charging. A full charge takes approximately six hours.

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3.0 Functional Controls and Indicators

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3.1 Acquire/Lock
The “GNSS LOCK” indicator LED provides a quick reference for the status of the
GNSS lock, as well as the Rubidium Oscillator status.
There are five conditions which are indicated:
When the GNSS is locked and is producing a disciplining PPS to the Rubidium
oscillator, the “GNSS LOCK” indicator will be illuminated solid Green. This
indicates that the frequency of the Rubidium is within the threshold loop variance.
The solid green also indicates the Rubidium physics package is functional, self-
test has passed and the frequency is stable. Once the Rb and GNSS functions
have locked, the process of disciplining the atomic clock to GNSS begins. This
process has a time constant on the order of 1000 seconds. Therefore, the
accuracy of the disciplining process is very much dependent upon the time spent
in the disciplining mode. The loop variance threshold can be user defined. Refer
to the Programmer’s Guide.
A single blink in a green “GNSS LOCK” illumination indicates that the GNSS is
locked and is producing a disciplining pulse to the Rubidium, but the Loop
Variance is outside the specified parameters, or the Rubidium is not locked. On
startup, one blink indicates the GNSS receiver has acquired a sufficient number
of satellites to generate the PPS pulse. Once acquired, timing can be
maintained with a single satellite.
A double blink in a green “GNSS LOCK” illumination indicates that the GNSS
receiver is not locked, does not have enough satellites for lock, or is tracking
towards lock. The receiver is not producing a PPS to discipline the Rubidium, so
there is insufficient information to determine health of the frequency loop.

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A single RED flash in an illuminated green “GNSS LOCK” indicator warns the
user that, even though GNSS lock has been achieved, the Rubidium discipline is
disabled. The GNSS PPS pulse is active and available, but it is not disciplining
the Rubidium. This is the case if the user has the RBDiscipline setting disabled in
the Menu Screen or via the serial port. See the Menu Settings and the
Programmer’s Guide for how to enable/disable the Rubidium Discipline setting.
3.2 Battery
The battery is a 2-cell Lithium ion. It is designed to provide approximately six
hours of service. To achieve maximum service, start with a charged battery
(about six hours of charge time).
3.2.1 Fuel Gauge
There are three LEDs that give an approximate status of how much charge is in
the battery. The LEDs are set to approx. 30%, 60% and 80%. The gauge is
accurate to ~±10%. The Fuel Gauge is activated by depressing the BATTERY
CHECK button. Battery Voltage can also be monitored via the serial port,
$GPNVS,9 string, ninth field. This provides a voltage measurement that is +/-
20mV.
3.2.2 Charging
Indicates the battery is charging. Charging occurs when the unit is connected to
the external power source. The external power source can be the provided
power adapter or a 12Vdc (11Vdc to 15Vdc, 3A nominal source). The unit will
operate while being charged.

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3.2.3 Fail/Temp
This indicator is active if the battery is beyond its operating temperature range,
cannot be charged, or the charger has entered sleep mode. The battery can be
charged in the temperature range of 0 to 40 C.
The battery can be easily replaced. It is attached to the bulkhead with Velcro and
there is a simple three terminal connector. There is sufficient room in the battery
compartment for a spare.
The unit comes with a magnetic mount antenna with an attached three-meter
cable. The cable is stored in the antenna compartment and can be extended as
required. The antenna has a built in LNA with 28 dB of gain to improve the
receiver performance. The receiver provides 3.3Vdc to the antenna to power the
LNA and a maximum current of 45 ma. The provided antenna can be
disconnected, and another used provided it can operate within the DC power
capability of the antenna power supply (3.3Vdc, 30mA). The two indicators turn
red if the antenna is detected as being shorted or open. There is a right angle
SMA adapter provided. The adapter provides a more direct antenna connection
and, more importantly, extends the life of the SMA bulkhead connector by being
used for the more frequent connections and disconnects and can be easily and
inexpensively replaced.
3.3
Antenna

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3.4 NTP time server option
When first turned on, the time server will try to establish an IP address for the
unit. Procedure and software required are described in Section 14. The default IP
address is shown on the IP Address Menu. The IP Address and other network
settings can be configured with a terminal connection, eg PuTTY.

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3.5 NT9400 Display and Menu Navigation
3.5.1 NEXT and SELECT buttons, LCD Menus
The LCD is used to provide information regarding the status of the NT9400,
network configuration, and Event history. The NEXT and SELECT buttons are
used for navigation of the LCD based menus and displays. Pressing the NEXT
button will advance the display to the next screen or menu. The select button is
used to navigate further options in each menu.

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3.5.2 Standard Screen
During normal conditions, the display shows time and GNSS lock status. Time is
UTC by default but can be changed to local time via the NEXT and SELECT
buttons by simply following the prompts in the “UTC Offset” Menu. The display
will also indicate the number of satellites in view, and the number of satellites
acquired, and whether the unit is in a lock condition. The display remains
operational at all times.
The time is presented as UTC. The time format can be changed to 12 hour or 24
hour format from the “UTC Mode” menu screen, and the time zone can be
changed from the “UTC Offset” menu when the unit is GPS locked.
Note that the changes to UTC Offset will be reflected in both NMEA output, IRIG
output and display. The time is read and updated from the ZDA NMEA string,
which also contains the offset value. If the user needs to verify offset in the
output data, refer to the ZDA string.

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Example:
$GPZDA,081231.000,22,03,2018,-06,00*7C
The ZDA string indicates a time of 08:12:31, on March 22, 2018.
The offset, “-06:00”, indicates that the time displayed is actually UTC–06:00.
The Event output also logs the events to reflect the offset time. The “local” time
zone is used to mark the event, and the UTC offset is included in the event
output.
Example:
$E,001,P,08:15:54.16820285-06:00,39055972N094261191W,032218*1C
“001”: The event number is 001 out of 512 events.
“P”: The event was triggered by the push button EVENT TEST.
“08:15:54.16820285”: The event time in 24 hour format hh:mm:ss.dddddddd.
“-06:00”: The offset from UTC.
“39055972N”: Latitude in dd.mm.mmmm (decimals removed) + direction.
“094261191W”: Longitude in ddd.mm.mmmm (decimals removed) + direction.
“032218”: Date in mmddyy.

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3.5.3 Orange Screen
This screen shows the Date/Time information in a specific user defined format:
The top row shows the Date in DDMMYYYY format. This is followed by a “T”
indicator, followed by the time in hhmmss format.
If the time format is 12hr, the bottom row will start with AM or PM. If the time
format is 24hr, the space will be blank.
The TZ “Time Zone” is shows UTC offset: ±hh:mm.
The SV “Satellites in View” is followed by the number of satellites that the GNSS
receiver is currently reporting.
3.5.4 Position Screen
This screen displays the current Latitude and Longitude of the unit, as last
observed by the GNSS receiver.