System and method for maintaining a common sense of time on a network segment
First Claim
1. A method for time synchronization of field devices on a network of a distributed control system, the method comprising:
- transmitting periodically timing information from a master clock to the field devices over the network of the distributed control system; and
adjusting an output clock signal frequency and a time stamp of each field device as a function of the periodically transmitted timing information and an output clock signal local to each field device.
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Accused Products
Abstract
The system has a control center, a time master device and a plurality of distributed, time slave field devices in synchronization with a master clock of the time master device. The time master device periodically transmits a time distribution data unit. Each time slave field device has a timer adjustment element, a fixed rate clock and a variable clock. The timer adjustment element calculates a frequency ratio between the master clock and the fixed rate clock and uses the frequency ratio to calculate adjustment coefficients to adjust a local sense of time for each field device, such that a time stamp of each field device is synchronized to the master clock.
69 Citations
21 Claims
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1. A method for time synchronization of field devices on a network of a distributed control system, the method comprising:
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transmitting periodically timing information from a master clock to the field devices over the network of the distributed control system; and
adjusting an output clock signal frequency and a time stamp of each field device as a function of the periodically transmitted timing information and an output clock signal local to each field device. - View Dependent Claims (2, 3, 4, 5)
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6. A method of synchronizing a local sense of time of each of a plurality of field devices to a clock of a master field device on a segment of a control network using a time distribution data unit, the method comprising:
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detecting the time distribution data unit on the segment of the control network;
calculating a frequency ratio between the local sense of time of a field device and a sense of time of the master field device; and
adjusting as necessary the sense of time of the field device according, to the frequency ratio. - View Dependent Claims (7, 8, 9, 10, 11)
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12. A process control system having a common sense of time, the system comprising:
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a control network;
a time master device in communication with the control network and having a master clock for generating a master clock signal, the time master device for periodically transmitting a time distribution data unit representative of the master clock signal; and
a plurality of time slave devices in communication with the control network, each time slave device having a local clock, and a time adjustment element for adjusting the local clock according to a frequency ratio between the master clock signal and an output clock signal of the local clock. - View Dependent Claims (13, 14, 15, 16, 17)
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18. A method for reducing time processing cycles in distributed field devices of a process control network, the method comprising:
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calculating adjustment coefficients for each field device according to a difference in frequencies between a local clock of each field device and a master clock of a time master device on the process control network; and
adjusting a sense of time of each field device as needed to synchronize a sense of time of each field device with the time master device. - View Dependent Claims (19, 20, 21)
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Specification