Master clock
As a master clock , the master clock , a Central or standard clock in an becomes the clock system that AM denotes that any number of ancillary controls or daughter watches and thereby an exactly synchronous ensures passage way all connected watches. This is important for uniform timing within companies, authorities, schools and other public buildings.
The principle was invented and implemented by Carl August von Steinheil in 1839 .
A second meaning of main clock means an evacuated precision pendulum clock , which apart from a temperature-compensated seconds pendulum contains no moving parts. To avoid mechanical malfunctions, these are outsourced to a slave clock synchronized with the master clock (see Riefler and Shortt clocks ). This made it possible to achieve accuracy of less than 0.01 seconds per day for time services long before quartz watches .
Layout and function
The master clock is the most important part of a clock system; their task is to control slave clocks and additional signaling devices. It is usually not set up in a place where the display or the dial is clearly visible, but in a control room , together with the rest of the communication technology or electrical installation .
Master clocks have a particularly accurate within the respective technology transition . The master clock consists of the clockwork and the drivers for the slave clock lines. At regular time intervals, usually every minute, a short control signal is sent to the subordinate slave clocks, which there drive the hands via a stepper motor . In order to reduce the effects of interference on the line that could impair the synchronization of the clocks, successive control signals with opposite polarity are sent out. In older clocks, the polarity of the control signal is reversed by a pole reversing relay .
In practice, especially in large systems, several slave clock lines are set up, to each of which a certain number of slave clocks can be connected. Each line can be adjusted individually and, if necessary , monitored for faults such as short circuits , earth faults or interruptions .
Executions
| Accuracy of mechanical master clocks | ||
|---|---|---|
| Pendulum design | Clockwork | |
| ¾-second pendulum | Wooden pendulum | ± 30 sec / month |
| Invar steel pendulum | ± 10 sec / month | |
| Seconds pendulum | Wooden pendulum | ± 15 sec / month |
| Invar steel pendulum | ± 6 sec / month | |
| Shortt and Riefler pendulums | ± 3 sec / month | |
Until the advent of quartz-controlled clocks, the movement of master clocks consisted of precision mechanics . The course could be regulated by a precisely adjustable pendulum and stabilized by evacuated housing. To prevent the pendulum from changing in length in the event of temperature fluctuations and thus to reduce inaccuracies, it was often made of invar steel .
Mechanical master clocks are widely used as ¾-second pendulum versions and as 1-second pendulum versions. ¾-second pendulum clocks make up the majority. 1-second pendulum clocks are used particularly in clock systems in train stations and were the basis of astronomical time services until around 1960 .
In Germany, modern master clocks evaluate the time signal from the long-wave transmitter DCF77 in Mainflingen near Frankfurt am Main in order to synchronize with the legal time . In other countries there are or were comparable time services, for example the BEV in Vienna , the former HBG station Prangins in Switzerland or OMA in Prague .
Church clocks
Special master clocks with additional switching outputs and DCF77 time reception are usually used for churches . These control the tower clock (mostly 230 V), possibly slave clocks (12 V or 24 V with polarity changing) as well as outputs for chimes and chimes (pulse output for the striking mechanism ).
Some special functions for main church clocks:
- With melodic ringing, several ringing bells are switched on and off with a time delay (according to their size).
- When the clock strikes, a melody (e.g. the Westminster strike) and then the hour strike can be played every quarter of an hour.
- The striking mechanism lock, possibly with subsequent locking, prevents striking if the bell is still ringing or has not yet swung out.
See also
literature
- Harry Dittrich, Günther Krumm: Elektro-Werkkunde, Volume 5: Professional experience for telecommunications installers, telecommunications electronics technicians, telecommunications mechanics and telecommunications craftsmen with technical calculations and technical drawings. 5th, reviewed edition, Winklers Verlag, Darmstadt 1973.
Web links
- Holger Hannemann: main clock collection
- Axel Höfer: Mother watches - function and use
- Gerrit Eckardt: master clocks and mother clocks
- Master clocks and time switches . Nod electronics
- Clock systems . DDR computing technology
Individual evidence
- ↑ VDE Committee "History of Electrical Engineering": Chronicle of Electrical Engineering, keyword: Steinheil ( Memento of the original from May 9, 2016 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. www.vde.com, accessed on May 8, 2016
- ↑ JE Bosschieter: The evolution of electric clocks, Part B: The first inventor. www.electric-clocks.nl, accessed on May 8, 2016
- ↑ Nicke Electronics, master clocks for churches
