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Time synchronization

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  • Информационные материалы

    Информационные материалы

    Introduction

    In many applications it is becoming increasingly important to synchronize the time in plants and systems. Only if all network stations are supplied cyclically with a reliable time frame from a central location can optimum process operation be ensured. This results in benefits for the plant operator such as increased operational reliability, the possibility of tracing system faults in a targeted manner, increased economic efficiency due to fewer production outages, and increased productivity in manufacture.

    For this purpose, the SICLOCK product family offers a comprehensive range of optimally matched components for setting up highly reliable time synchronization systems.

    Typical industries and fields of application for time synchronization systems are:

    • Factory/process automation
    • Power supply
    • Building automation
    • Transportation systems
    • Safety engineering
    • IT systems

    The SICLOCK product range comprises the following product groups:

    • Wireless receivers
    • Central plant clocks
    • Pulse converters
    • Accessories

    SICLOCK time synchronization

    System description

    Satellites or long-wave transmitters are used as primary time sources. The SICLOCK wireless receivers (e.g. SICLOCK GPS1000) receive these high-frequency signals and transmit the demodulated time signal to the central plant clock via a robust and interference-proof 2-wire connection.

    The central plant clock converts the time signal into an Ethernet-based network frame (e.g. NTP, SIMATIC procedure) and thus provides all connected network stations with precise and uniform time information.

    Furthermore, in the event of failure or loss of reception from the primary time source, the central plant clock ensures stable continuation of the clock time and tracking of the system time without time jumps as soon as reception is restored.

    SICLOCK TC400 central plant clock with SICLOCK GPS1000 wireless receiver

    Область применения

    Application examples

    System with GPS reception

    SICLOCK TC400 central plant clock with SICLOCK GPS1000 wireless receiver

    The SICLOCK GPS1000 wireless receiver (Article No. 2XV9450‑1AR84) is used in this example. The wireless receiver is mounted outdoors with "visual contact" to the navigation satellites for optimum reception quality.

    The line current method (TTY - 20 mA) used in the SICLOCK system permits distances of up to one kilometer between the wireless receiver and the central plant clock and also supplies the receiver with power, which eliminates the need for any additional power supply components. This makes it possible to install the central plant clock at a central location, even in plants spread over a very large area.

    The SICLOCK TC400 central plant clock shown in the example features four 10/100 Mbit Ethernet interfaces for supplying up to four independent IP networks. The SICLOCK TC100 central plant clock with one Ethernet interface has been designed for smaller, cost-sensitive plants.

    The central plant clocks do not have Ethernet switching functionality for safety reasons. SIMATIC NET SCALANCE X switches are recommended for this purpose, see http://support.automation.siemens.com/WW/view/en/18689247/133200.

    System with DCF77 reception

    SICLOCK TC400 central plant clock with SICLOCK DCFRS wireless receiver

    As an alternative to receiving satellite signals, the DCF77 time signal transmitter can be used as primary time source. The transmitter is located near Frankfurt am Main and transmits long-wave signals at a frequency of 77.5 kHz. Under normal conditions, reception is possible up to a distance of about 1 500 km from the transmitter.

    The SICLOCK DCFRS wireless receiver with TTY output (Article No. 2XV9450‑1AR16) is used in this application. Here too, a separate power supply is not required if a SICLOCK TC100 or SICLOCK TC400 central plant clock is used.

    The advantages over satellite reception are lower costs and the option of mounting the receiver inside a building. The last advantage is especially useful if outdoor installation is not advisable, e.g. due to risk of vandalism.

    Redundant modes

    Due to the importance of having a reliable time supply in many demanding applications, the SICLOCK system offers optional redundant modes to further increase plant reliability. The redundancy can be on the reception side, the network side, or even be combined with a redundant central plant clock for highly sensitive applications.

    Reception-side redundancy

    SICLOCK TC400 central plant clock with SICLOCK GPS1000 and SICLOCK DCFRS wireless receivers

    In this application, SICLOCK GPS1000 and SICLOCK DCFRS wireless receivers are used in parallel. External time information can continue to be received even if one of the two primary time sources fails. The SICLOCK TC100 and SICLOCK TC400 central plant clocks each have two inputs for the wireless receivers.

    Highly redundant system

    SICLOCK TC400 central plant clocks with SICLOCK GPS1000 wireless receiver

    This application can satisfy the highest redundancy requirements. The system uses two SICLOCK TC400 central plant clocks, each with separate SICLOCK GPS1000 wireless receivers

    One central plant clock is parameterized as the NTP server master, the other as the NTP server slave. The NTP server slave takes over if the NTP master or the connected wireless receiver fails.

    If SICLOCK GPS1000 wireless receivers are used, they should be mounted as far away from each other as possible so that the receiver with the better reception conditions can be used and, for example, to avoid damage to both receivers in the event of a lightning strike. Instead of using two GPS wireless receivers, one SICLOCK DCFRS wireless receiver can of course be used.

    Synchronization of IT networks

    IT network with a central plant clock

    SICLOCK TC100 central plant clock with SICLOCK GPS1000 wireless receiver: Synchronization of IT systems (with failure protection)

    This application can be used for the synchronization of a large number of IT devices. The cost-optimized SICLOCK TC100 central plant clock can be used if all the stations that have to be synchronized belong to the same IP subnet. A wide range of SCALANCE X Ethernet switches is available for selection according to the number of terminal devices to be synchronized; see http://support.automation.siemens.com/WW/view/en/18689247/133200.

    Simple solution without failure protection for the direct supply of clock time to IT systems

    SICLOCK GPS1000 PS pulse converter with SICLOCK GPS1000 wireless receiver, synchronization of IT systems (without failure protection)

    Direct connection to an IT system can be considered in applications with low failure protection requirements.

    All of the required components are included in the SICLOCK GPS1000 package (Article No. 2XV9450‑1AR82). The scope of delivery includes the SICLOCK GPS1000 wireless receiver with antenna base, the SICLOCK GPS1000 PS pulse converter, and a receiving software that runs on Windows systems.

    Дальнейшая информация

    For more information, go to

    • http://www.siemens.com/siclock
    • E-mail: siclock@siemens.com