Pulse-per-second signal: Difference between revisions
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A '''Pulse per second''' (PPS) is an [[electrical signal]] |
A '''Pulse per second''' (PPS) is an [[electrical signal]] that very [[precision|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 milliseonds. |
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== Uses == |
== Uses == |
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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 an |
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 an 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. |
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== External links == |
== External links == |
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Revision as of 21:48, 30 April 2006
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 milliseonds.
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 an 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.
External links
GPS receivers that provide a PPS signal:
- 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: