Pulse per second

Pulse per second

A Pulse per second (PPS) is an electrical signal that very precisely indicates the start of a second. PPS signals are output by various types of precision clock, including some models of GPS receivers. Depending on the source, properly operating PPS signals have an accuracy ranging from a few nanoseconds to a few milliseconds.

Uses

PPS signals are used for precise timekeeping and time measurement. One increasingly common use is in computer timekeeping, including the NTP protocol. Because GPS is considered a stratum-0 source, a common use for the PPS signal is to connect it to a PC using a low-latency, low-jitter wire connection and allow a program to synchronize to it: this makes the PC a stratum-1 time source. Note that because the PPS signal does not specify the time, but merely the start of a second, one must combine the PPS functionality with another time source that provides the full date and time in order to ascertain the time both accurately and precisely.

ee also

* Precise Time and Time Interval (PTTI)

External links

GPS receivers that provide a PPS signal:
* [http://www.garmin.com/products/gps18oem/ Garmin GPS 18] , LVC (barewire) edition only. Offered in 1-Hz and 5-Hz formats.

Sites that describe how to use the PPS signal to set precise time on a PC:
* In OpenBSD 4.1 [http://www.openbsd.org/cgi-bin/man.cgi?query=nmea&manpath=OpenBSD+Current the nmea(4) line discipline] can [http://www.openbsd.org/cgi-bin/man.cgi?query=nmeaattach&manpath=OpenBSD+Current attach to a GPS timer] and optionally use the PPS signal for low jitter and high accuracy in system time and NTP time
* [http://gpsd.berlios.de/ gpsd — a GPS service daemon] , required to activate PPS signal on some devices (works in conjunction with OpenBSD's nmea line discipline if installed via ports tree and a stand-alone service daemon for other operating systems)
* [http://time.qnan.org Using a Garmin GPS 18 LVC as NTP stratum-0 on Linux 2.6]
* [http://www.david-taylor.myby.co.uk/ntp/FreeBSD-GPS-PPS.htm Adding a FreeBSD NTP server based on an GPS 18 LVC device]
* [http://tools.ietf.org/html/rfc2783 RFC 2783 Pulse-Per-Second API for UNIX-like Operating Systems, Version 1.0]


Wikimedia Foundation. 2010.

Игры ⚽ Поможем написать реферат

Look at other dictionaries:

  • Pulse-position modulation — is a form of signal modulation in which M message bits are encoded by transmitting asingle pulse in one of 2^M possible time shifts. This is repeated every T seconds, such thatthe transmitted bit rate is M/T bits per second. It is primarily… …   Wikipedia

  • Pulse generator — Pulse generators can either be internal circuits or pieces of electronic test equipment used to generate pulses. Features Simple pulse generators usually allow control of the pulse repetition rate (frequency), pulse width, delay with respect to… …   Wikipedia

  • Pulse repetition frequency — (PRF) is the number of pulses transmitted per second by a radar. The reciprocal of this is called the Pulse Repetition Time (PRT), Pulse Repetition Interval (PRI), or Inter Pulse Period (IPP), which is the elapsed time from the beginning of one… …   Wikipedia

  • pulse wave — n the wave of increased pressure started by the ventricular systole radiating from the semilunar valves over the arterial system at a rate varying between 20 and 30 feet (6.1 and 9.1 meters) per second in different arteries * * * the elevation of …   Medical dictionary

  • Pulse detonation engine — A pulse detonation engine, or PDE , is a type of propulsion system that can operate from subsonic up to hypersonic speeds. In theory the PDE design can produce an engine with a burn efficiency higher than other designs, with considerably fewer… …   Wikipedia

  • Pulse-code modulation — PCM redirects here. For other uses, see PCM (disambiguation). Pulse code modulation (PCM) is a method used to digitally represent sampled analog signals. It is the standard form for digital audio in computers and various Blu ray, Compact Disc and …   Wikipedia

  • Pulse jet engine — A pulse jet engine (or pulsejet) is a very simple form of internal combustion engine based jet engine where combustion occurs in pulses. A typical pulsejet comprises an air intake fitted with a one way valve, a combustion chamber, and an… …   Wikipedia

  • Pulse dialing — Middle 20th century rotary dial telephone Pulse dialing, dial pulse, or loop disconnect dialing, also called rotary or decadic dialling in the United Kingdom (because up to 10 pulses are sent), is pulsing in which a direct current pulse train is… …   Wikipedia

  • pulse — 1 noun 1 (countable usually singular) 2 a) the regular beat that can be felt, for example at your wrist, as your heart pumps blood around your body: I checked his pulse he was still alive. b) also pulse rate the number of these beats per minute:… …   Longman dictionary of contemporary English

  • Pulse~Link — Infobox Company type = Privately held company name = Pulse LINK, Inc. company foundation = 2000 location = key people = Waddah Al Mousa, Chairman; John Santhoff, CEO CTO; Bruce Watkins, President num employees = 75 industry = Fabless… …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”