Shulou(Shulou.com)06/02 Report--

Brief introduction of gps Satellite time Calibration system

Through the GPS clock server set up in the local area network, the satellite time correction system receives the standard time on the GPS satellite, and through accessing the local area network, sends the standard time to each workstation connected to the network with TCP/IP protocol, and verifies the time of each workstation synchronously, so as to provide an accurate standard time benchmark and solve the problem of inaccurate and non-synchronous time of each workstation. It avoids unnecessary losses caused by time errors, and the time of the system is completely synchronized with Beijing time; at the same time, the system can also drive the sub-clock display screen and LCD liquid crystal display to display the time, which is convenient for the staff to check the time.

Working principle of satellite time correction system

The overall design scheme of the time calibration system is that both hardware and software adopt the popular client / server mode of the network. The time server running the server-side timing software broadcasts the standard time to each display terminal through the local area network with standard TCP/IP and other network protocols. The client time calibration software running on each network terminal synchronizes the local time with the clock synchronization server in the local area network, thus realizing the complete synchronization of the whole local area network time.

GPS satellite time is used as the signal time acquisition source, the original data output by GPS receiver is read, the time and related information are extracted after processing, and the time server is uploaded. At the same time, the system also has a network exit, which can drive some large LED digital tubes or some LCD terminals through the local area network, and display the time in some public places, such as machine tuning room, so as to facilitate the staff to read the time.

Because GPS has strong anti-jamming ability, works all-weather and is not affected by the weather, so this system chooses it as the time reference source. The front end with the GPS control box as the core and the external GPS satellite antenna is responsible for receiving the satellite signal transmitted by the satellite to the ground. After demodulation and processing, the output original satellite time data is sent to the time server through the RS-232 interface.

The local area network time server is served by a PC connected to the local area network. It is equipped with server-side software of network time synchronization system. The time server not only completes the extraction of time information from the original satellite data received by the serial port, and proofreads its own date and time, and provides a time calibration benchmark for other computer terminals on the local area network, but also automatically searches the TCP/IP display terminal in the whole local area network, and refreshes and proofreads the time and date of each TCP/IP display terminal according to the synchronization period set in advance.

Composition of synchronous clock system

Clock server

SYN2136 clock server is a time server based on Linux system that supports NTP/SNTP protocol. This clock server receives GPS satellite timing signals and provides accurate, standard, safe, reliable and multi-functional time services for network equipment (users) through NTP/SNTP protocol. The front panel displays information such as year, month, day, hour, minute and second, number of receivers and working status.

Product function

1) provide 1 physically isolated NTP network time service interface

2) the front panel shows the year, month, day, hour, second, number of satellites and working status

3) support time synchronization in windows, LINUX, UNIX, SUN SOLARIS, IBM AIX and other operating systems

4) the satellite timing system supports the DHCP function. All the network equipment connected to the satellite timer can automatically obtain the IP address of the satellite timing system, thus achieving the clock synchronization function.

5) support multiple time servers or multiple network ports can be set to the same IP, redundant backup each other

6) Parameter management mode that supports WEB and SSH encrypted communication and software monitoring settings

7) Parameter settings files can be exported and imported

8) switch between Chinese and English on the network configuration page, setting username, password and hostname

9) Real-time monitoring of load, elapsed time, real-time traffic and memory status

10) the built-in clock source can be selected as temperature compensation crystal oscillator, constant temperature crystal oscillator, rubidium atomic clock and taming module, etc.

11) Serial time service, sending time information of hour, minute, second, year, month and day once per second

12) output timing synchronization signal (1PPS), TTL interface output

The function and timing Mode of GPS clock Server

GPS is widely used in network synchronization, data synchronization and other fields that need timing, timing and punctuality. It has high stability, no accumulated error, is not limited by regional climate and other environmental conditions, and is easy to use. It can provide accurate time information around the clock. The GPS receiving module receives accurate time information from the satellite, and after coding, it provides time information and second pulse signal to the network clock server through the RJ45 interface.

There are generally two kinds of timing modes for GPS clock servers: point-to-point timing and hierarchical timing.

(1) in the point-to-point time mode, the external GPS clock server is set to the first NTPServer, and the system server is used as the second NTPServer. That is, all the devices of the system (controller, engineer station, operator station, etc.) are first synchronized with the GPS clock server. When the GPS is not working or the network is not working, the time is synchronized by the system server of Ovation itself. Because of the large number of clients, this method requires a high level of GPS clock server. It is precisely because all equipment directly give priority to timing, compared with the hierarchical timing mode, the danger is dispersed.

(2) the hierarchical timing mode sets the two computers of the system as the client of GPS, which is directly synchronized with GPS and serves as the NTPServer of other devices in the Ovation system. This method greatly reduces the burden of the GPS clock server, but has higher requirements for the operator station or engineer station of the NTP Server.

Point-to-point timing mode and hierarchical timing mode have their own characteristics, and the scheme chosen depends on the performance and quality of the equipment selected, such as GPS clock server, operator station or engineer station. The choice of either way depends on the safe and reliable operation of the GPS clock server.

An example of satellite time synchronization system

SYN2136 clock server. The server has built-in Beidou dual-mode time service module, which takes GPS/ Beidou signal as the time benchmark, and synchronizes all computers, servers, DVR, NVR, controllers and other devices in the network with NTP/SNTP protocol to achieve network time unification.

The SYN2136 clock server uses high precision GPS receiver / Beidou second generation receiver signal input to provide high reliability time reference signal, and adopts high-tech operation method to make the time synchronization signal output by the timekeeping circuit be precisely synchronized on the GPS/ Beidou input time reference, and output high precision synchronization signal with excellent short-term and long-term stability.

The time server adopts modern high-tech taming algorithm to keep the frequency signal in the oscillator synchronized with the satellite with high precision. Because the output second pulse time signal of the BNC port output by the timing server is the second signal output of the oscillator, it is synchronized with the satellite signal but is not affected by the jump of the satellite second pulse signal.

This clock server adopts modern high-tech surface mount technology, no hard disk design, is not limited by regional climate and other environmental conditions, cost-effective, simple operation, maintenance-free and other characteristics, suitable for unattended. This product can provide precision standard time signal and time stamp service for computer network, computer application system, process control management system, e-commerce system, online B2B system, database preservation and maintenance, hard disk video recorder and other intelligent devices.

Implementation content

SYN2136 ntp time synchronization server receives GPS satellite signal and Beidou second generation satellite signal to generate second pulse, serial time information signal and network time service interface. the system automatically saves all kinds of configuration information. it is a practical electronic instrument to establish time scale and realize time synchronization.

Installation of antennas

This equipment uses the GPS/ Beidou satellite signal receiving antenna as an integrated receiving antenna, even with an antenna receiver (head) with an antenna feeder of 30 meters in length, and the antenna receiver is a passive antenna.

The antenna should be erected on the outdoor / balcony / balcony. The field of view of the white mushroom head should not be obstructed in order to avoid interference to the satellite. The antenna does not need separate power supply and is powered by the feed on the mainframe.

Pre-installation preparation

1. Check whether the antenna is complete, check whether the connector of the antenna is loose or fall, (if so, please contact the manufacturer in time for replacement)

2. Check whether the various interfaces of the equipment are reliable, such as network port, serial port, grounding post, etc.

3. When the front panel of the equipment shows that the satellite cannot be received, change the white mushroom head to a few more positions to try the star collection effect, so as to eliminate the problem of the antenna or the equipment.

4. Check whether the accessories are complete, such as power cord, antenna, antenna bracket, expansion screw, CD-ROM, serial cable and so on.

Boot steps and boot display

Prepare before electrification

A) remove the instrument from the packing box and place it flat on the console or cabinet.

B) the inspection of the power supply shall comply with the rated requirements, relevant specifications and the provisions of Article 3.3 of this note.

C) erect the antenna in the open area such as the roof.

D) check that the rear panel power switch of the machine should be in the disconnected position and connect to the power supply after confirmation

E) in the case of power off (shutdown), access antenna and output signal connection line, etc.

LCD information display after power on

The front panel LCD provides date and time information display to the user. Date and time information includes year, month, day, hour, minute and second. The LCD screen on the front panel shows the time as Beijing time.

When the machine is turned on (cold start), the display is as follows:

Subsequently, the "1PPS" indicator lights up once a second.

After about 3 seconds, the clock starts at 08:00:01. It is shown as follows:

When the satellite signal is received and the time is valid, the LCD displays as follows (example figure):

The row above the LCD shows that the number of stars collected by GPS is 10, and that of Beidou is 10, and the time state is valid.

If it is displayed as:

It indicates that the satellite signal is not received at this time, or the antenna has been disconnected.

Because the machine automatically maintains the original time after receiving the correct reference time for the first time, the LCD interface is still "A", indicating that the current output time of this machine is still valid and can be used.

Installation of equipment

1. The equipment is a standard 1U chassis and can be installed in a standard cabinet by installing screws.

2. Install the white section of the time service antenna on the antenna bracket and fix it on the top of the house or platform or terrace by expanding screws or using it, to ensure that there are no obstacles (such as big trees, signal transmission towers, tall billboards, etc.) around the white mushroom head.

3. Insert one end of the power cord into the power supply of the equipment, and then insert the three-phase power supply at the other end of the power supply into the AC220V power supply.

4. After confirming that it is correct, press the switch of the device, and the screen of the device lights up, which proves that the device starts normally.

5. Connect a network cable, one end is connected to the network port behind the device, and the other end is connected to the core switch. Interfaces marked with "reserved" are not available.

Trial operation scheme

The trial run phase is after the project development and implementation phase, and after passing the overall system initial inspection, it can enter the trial operation phase, and the system trial run lasts for one week.

Principles to be followed in trial operation:

1. During the trial operation, synchronous technology will take full responsibility for the system and all equipment: ensure that any defects or failures of the system or equipment are repaired within 24 hours (holidays and holidays are no exception); if the defects or failures of the system and equipment are very serious, the trial operation will be resumed after repair.

2. The work in the trial operation phase includes: examining the operation function, stability and reliability of the equipment and system through the open use of users, and carrying out necessary manual simulation tests.

3. During the trial operation, synchronous technology will repair, correct or replace any equipment that does not meet the requirements of the technical specification.

4. After the trial operation of the system is completed, the project acceptance phase can be entered.

The scope of the trial operation includes all subsystems. We will discuss the work in the trial operation phase from two main aspects: the trial operation plan and the management measures.

Quality assurance system

With years of accumulation in the time-frequency industry, synchronous technology has precipitated and organized very advanced industry standards, project management and quality management systems, and has very mature management concepts and tools in quality assurance, such as the audited 9000 certification.

For this project, Synchro Technology will send senior internal supervision team and project manager to participate in the project quality management, and the head of the internal supervision team will serve as the project quality manager, responsible for ensuring that the project complies with the standard requirements of the quality assurance system to ensure the synchronization accuracy and synchronization effect of the delivered ntp time synchronization server, design and management quality and many other aspects.

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