초록 ▼

A method for transposing the time of an event as read at a remote station with one clock to the time frame of another clock at a master station when the clocks are not synchronized and are of insufficient accuracy to provide measurements to within a few microseconds relative to other time measuremen

A method for transposing the time of an event as read at a remote station with one clock to the time frame of another clock at a master station when the clocks are not synchronized and are of insufficient accuracy to provide measurements to within a few microseconds relative to other time measurements which are likewise transposed to refer to the master clock. A list of TV line 10 synch pulse times are maintained at the master for a specific number of recent line 10 pulses. Along with the time reading for the event, the line 10 synch pulse time as read at the remote is sent to the master. The list of line 10 synch times maintained at the master is examined to find the time by the master clock for the same line 10 and the difference between the time by the remote clock and the time by the master clock is used as an indication of the time correction factor to be applied for the transposition. The time correction factor is compensated for the difference in propagation time for the TV signal transmission to the master as compared to the remote. The transposed time reading is compared to other transposed readings obtained from other remote stations to either determine the sequence of several events at the different remotes or to obtain a measure of quantities such as voltage phase angle or the position of a fault. Updating of the time correction factors is provided to compensate for drift of the clocks.

대표청구항 ▼

A method for correlating time tags associated with events of interest detected at any of a plurality of remote stations in a digital data acquisition system having a master station connected to receive data from said plurality of remote stations where said time tags represent the data gathered at th

A method for correlating time tags associated with events of interest detected at any of a plurality of remote stations in a digital data acquisition system having a master station connected to receive data from said plurality of remote stations where said time tags represent the data gathered at the remote stations indicating the time of occurrence of each of said events as obtained by reference to an unsynchronized clock at the remote station detecting the occurrence of the event and the correlation is to time as kept by a clock at the master station, to make possible a time ordering of events at different remote stations, comprising the steps of: maintaining at said master station a list of line 10 synch pulse times from a single television station as determined from the master clock for a predetermined number of line 10 synch pulses previous to the last most recent line 10 synch pulse received; transmitting at each of a sequence of interrogatory periods (n) and periodic update periods (u) from said master to said remote stations message requesting information on time tagged events at said remote stations; producing and transmitting to said master during said interrogatory periods (n) at each remote station in response to said messages a signal constituting a reply message incorporating as a first signal the time tags, Tr(E)(n), for the events information requested, and as a second signal the line 10 synch times at the remote stations, Tr(S)(n), for the line 10 synch pulse previous to each of the events; producing at said master station a third signal, Td, representative of the difference in propagation time from the TV transmitter to the remote station as compared with the master station; producing at each interrogatory period at said master station a time correction factor, TCF(n), as a function of said second and third signals in accordance with the equation TCF(n)=Tm(S)(n)-Tr(S)(n)-Td, where Tm(S)(n) is the time established from said list for the line 10 synch pulse identified by the signal Tr(S)(n), said time Tm(S)(n) being identified on said list as that one which causes the resulting correction factor, TCF(n), to deviate from the previous correction factor, TCF(n-1), by a minimum as compared with the correction factors corresponding to the other times on said list; periodically updating the said previous correction factor, TCF(n-1) used to obtain the value of the present correction factor, TCF(n), to compensate for the drift of the clocks at the remote stations with reference to the master station; summing for each event said time correction factor and the first signal, representing the time tag Tr(E)(n), to produce a signal representing the correct timing of the events with reference to the master clock; and recording said correct timing signal for each event to provide a basis for time ordering a sequence of events occurring at different remote stations.