Meinberg USB 5131 User Manual

Technical Information
Operating Instructions

USB 5131

Driver Software for
Windows 2000/XP/Vista
Operating Systems

Impressum

Meinberg Funkuhren GmbH & Co. KG
Lange Wand 9
D-31812 Bad Pyrmont

Phone: ++49 52 81 - 9309-0
Fax: ++49 52 81 - 9309-30

Internet: http://www.meinberg.de
Email: [e-mail]

September 26, 2007

Inhaltsübersicht

Impressum ............................................................................................ 2

General information about DCF77 ....................................................... 5

Overview USB5131 ............................................................................. 6

Installation ............................................................................................ 7

Power Supply..............................................................................7

Aligning the antenna ................................................................... 7

Status LEDs ................................................................................ 7

Technical Specifications ....................................................................... 8

Physical Dimensions ................................................................... 9

CE Label ..................................................................................... 9

Content of the diskette ........................................................................ 10

Driver Diskette for Windows 2000/XP/Vista Operating Systems ...... 10

General information about DCF77

The radio clocks made by Meinberg receive the signal from the long wave transmitter
DCF77. This long wave transmitter installed in Mainflingen near Frankfurt/Germany
transmits the reference time of the Federal Republic of Germany. This time reference is
either the Central European Time (Mitteleuropäische Zeit, MEZ) or the Central Euro­pean Summer Time (Mitteleuropäische Sommerzeit, MESZ). The transmitter is control­led by the atomic clock plant at the Federal Physical Technical Institute (PTB) in
Braunschweig/Germany and transmits the current time of day, date of month and day of
week in coded second pulses. Once every minute the complete time information is
available.

At the beginning of every second the amplitude of the high precision 77.5 kHz carrier
frequency is lowered by 75% for a period of 0.1 or 0.2 sec. The length of these time
marks represent a binary coding scheme using the short time mark for logical zeroes and
the long time mark for logical ones. The information on the current date and time as well
as some parity and status bits can be decoded from the time marks of the 15th up to the
58th second every minute. The absence of any time mark at the 59th second of a minute
signals that a new minute will begin with the next time mark.

Our radio clocks decode the highly accurate information on date and time within a
wide range around Germany. So some of our clocks are installed in Bilbao/Spain as well
as in the city of Umeå in northern Sweden - fully satisfying the requirements of the users.
The radio clocks automatically switch to summertime and back. The reception of the
time information is free of charge and does not need to be registered.

Generally it is important to position the antenna in an optimal way. It should be
mounted at least 30 centimeters away from the clock unit and from solid steel. The
antenna should be aligned at a right angle to the direction of the transmitter (Frankfurt).

Figure: decoding scheme

Overview USB5131

The radio remote clock USB5131 has been designed for communication via the serial
USB interface. The required power is provided via the USB cable as well, so there is no
need for any external power supply.

The DCF77 signal received by the internal antenna is passed to the on-board LF
receiver where it is demodulated by a synchronous detector with automatic gain control.
The demodulated time marks from the receiver circuit are filtered and decoded by the
microprocessor. If no errors are detected in the current time message an additional
plausibility check against the previous time message is performed. If that plausibility
check passes, too, the real time clock on the board is adjusted corresponding to the
decoded time and date.

The USB5131 module provides two integrated LEDs, which show the demodulated
time marks (MOD LED) and the state of synchronisation (FR LED).

The scope of supply includes an USB cable with 3 mtrs. of length to connect the
USB5131 directly to a PC’s USB port.

Also included is the driver software for Windows 2000/XP/VISTA® operating sys­tems that is used to set the system time of the computer and shows some important status
information of the USB5131.

Driver software for other operating systems can be found on the Meinberg homepage
for download: http://www.meinberg.de/english/sw/index.htm

Front View USB5131

6

Installation

Power Supply

The USB5131 is powered via the PC’s USB port. After connecting the USB port the
radio clock is ready to operate. For proper operation it is essential to pay attention to the
following points.

Aligning the antenna

Generally, the exact alignment of the USB5131 module with its internal antenna is
important. It has to be placed in longitudinal direction to the transmitter (Frankfurt/Main),
see arrow printed on the label of the module. A distance of several meters to TV- or
computer monitors, to computers or microprocessor boards should be kept. These
devices can produce interference fields that lead to a poor or no DCF77 receiption. The
USB5131 should be installed with a minimum distance of 30cm to all metal objects.
Otherwise the ferrite antenna will be detuned and the received power decreases. If it is
not possible to archieve a sufficient reception with the internal antenna, it is possible to
connect an external antenna to find the optimal antenna location. An indoor antenna
AI01 or a weatherproofed outdoor antenna AW02 can be connected to the SMB
connector using a coaxial antenna cable with length of up to some hundret meters. An
external antenna is recommended whenever difficult conditions regarding the reception
reign. Alignment of the antenna (internal as well as external) can be done by watching
the modulation LED. Like described in chapter „General information about DCF77“,
undisturbed pulses per second (except 59. second) without any interfering pulses are
required for corrcect decoding of the DCF77 time telegram. Therefore, a modulation
LED blinking exactly once per second is a criterion for good receiption of the DCF­signal.

Status LEDs

The two LEDs „Mod“ and „FR“ reflect the state of synchronisation of the decoded time
marks of the USB5131. If the antenna is installed properly and the signal from DCF77
can be received without strong distortions, the green LED labeled Mod starts blinking
exactly once per second, corresponding to the time marks from DCF77. If this LED
flashes intermediately, there is some electrical noise around which prevents the micro­processor from decoding the time message. In this case, a better location for the antenna
must be found. After start-up, the red LED labeled FR (free running) indicates that the
clock is running on XTAL and has not synchronized with DCF77 yet. Due to the
plausibility checks, it can take up to three minutes after power-up until the clock is
synchronized and this LED is turned off. The state of this LED only changes when a
new minute begins. Without or with a disturbed RF signal the clock runs on XTAL with
an accuracy of 10
clock have lost reception for more than 12 hours the FR LED starts blinking.

-6

(after 24 hours of synchronous operation, otherwise: 10-5). If the

7

Technical Specifications

RECEIVER: narrowband straight receiver with automatic gain control

bandwidth: approx. 40Hz
reception via internal or external ferrite antenna

MODULATION: demodulated time marks indicated by LED

TIMECODE
CHECK: Multiple software check of the incoming timecode

Parity and consistency check over a period of two minutes

FREE RUNNING: Without RF signal the clock runs on XTAL with an

accuracy of 10-6 (after 24h of synchronous operation)
Disturbed reception indicated by LED

BATTERY
BACKUP: In case of supply voltage failure the on-board RTC keeps the time

based on XTAL for more than 150 hours (buffer capacitor)

RELIABILITY OF
OPERATION: Microprocessor supervisory circuit provides watchdog timer,

power supply monitoring and backup-battery switchover

INTERFACE: USB 1.1 (Universal Serial Bus)

TIME ZONE: CET/CEST (standard), always CET (without daylight saving),

UTC or east-european time (CET/CEST + 1h)

CONNECTORS: USB connector type B

SMB antenna connector (male)

POWER SUPPLY: 5V, via USB interface of the PC

current consuption: approx. 40 mA

HOUSING: plastic housing, IP30 protected

73mm x 117mm x 24mm (width x depth x height)

AMBIENT
TEMPERATURE: 0 ... 50°C

HUMIDITY: max. 85 %

8

Physical Dimensions

Plastic housing, IP30 protected, 73mm x 117mm x 24mm (width x depth x height)

CE Label

This device conforms to the directi ve 89/336/EWG on the
approximation of the laws of the Member States of the European
Community relating to electromagnetc compatibility .

9

Content of the diskette

The diskette contains a driver program that keeps the computer´s system time synchro­nous to the board time. If the present delivered diskette doesn’t include a driver program
for the operating system used, it can be downloaded from:

http://www.meinberg.de/english/sw/

On the diskette there is a file called „readme.txt“, which helps installing the driver
correctly.

Driver Diskette for Windows 2000/XP/Vista Operating Systems

10

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