Regional Composite Clock And Its Monitoring System

With the development of computer and the technique of network, in order to carry out their works successfully, many departments concerned such as railway department ,civil aviation department, operation headquarter department, scientific research department, earthquake observation and measurement department, satellite launching system, all need to adopt uniform time standard to communicate and coordinate among their each branch. Nowadays quartz clocks have been very popular , under normal atmospheric temperature,the frequency stability of quartz oscillator that quartz clock for civilian use adopt,usually under±10×10-6,its average instantaneous daily error usually under ±0.5S/D,in normal circumstances, its tick accuracy can satisfy the daily requirements of the public. Under the circumstances needed high accuracy, we can use temperature to make up quartz oscillator (frequency stability : 1～5×10-6) ,constant-temperature quartz oscillator ( frequency stability: 3～5×10-9) and atomic clock( it's maximum frequency stability can reach 10-14 order of magnitude ) ,etc. Generally speaking,one alone clock always exists accumulated error, as a result , it's unavoidable that each clock in the same system is not simultaneous. In such a system that time needs uniform and that higher accuracy clock is needed. Evidently it's not economical that adopts high accuracy clocks and calibrates each clock in certain way, e.g GPS. Thus, to those key departments, which need to conform to the requirement for the accuracy and synchronism of time, wide area slave and master clock control system which have high accuracy and reliability is always indispensable (in a synchronized clock system).The main tasks of this article are as follows: 1. The putting forward of this systematic devising project is according to the large area's requirement for the technique of clock system and the require- ment demanded by project trustor (the Branch Firm of Tianjin Clock Firm ) . This project is a master-slave distributed microcomputer monitor secondary and master clock system which consists of central equipment (including GPS, two primary master clock systems,auto-cut and monitor system). secondary master clock, sub clock (digital clock and mechanical clock) ,output system and power supply.This article devised all of the hardware and software systems.2. The division of the back-up power supply to avoid unexpected power cut. In order to bring primary master clock into full play,this article devise two sets of system ( one is in the operating condition ,the other is in a back-up condition ) . Their state is monitored and changed over by supervisory control system.3. The optical cable communication which adopts in the Primary master clock and secondary master clock increases not only the effectively transferring and controlling distance, but also the transmission's ability of anti-interference. The primary master clock adopts large screen liquid crystal display (LCD) and digital display. in addition, keyboard input makes the operation and control more conveniently, and makes the state of display more directly-viewed.