Two-wire signal transmission system
First Claim
1. A signal transmission system of the type used in process control systems for conveying a signal between a field instrument and a central controller, or between a central controller and a process control device, comprising:
- a transmitter arranged to accept an input signal;
converter means in the transmitter for developing a pulse width signal with a duration corresponding in a predetermined manner to the value of the input signal;
means in the transmitter for providing a transmission signal with two states, said means being responsive to the converter means to cause the duration of one of the transmission signal states to correspond to the duration of the pulse width signal;
a transmission line for carrying the transmission signal;
a receiver for receiving the transmission signal;
means in the receiver for developing an output signal with a duration corresponding to the duration of the one transmission signal state, whereby the duration of the output signal corresponds in said predetermined manner to the value of the input signal;
means, in one of the transmitter or receiver, for supplying power for the transmission signal; and
means, in the other of the transmitter or receiver, for deriving operational power from the transmission signal;
whereby the signal transmission system is able to convey signals less affected by noise, and is also able to convey operational power.
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Accused Products
Abstract
A signal transmission system of the type used in process control systems for conveying a signal between a field telemetering instrument and a central controller, or between a central controller and a process control device. The signal transmission system is arranged with a transmitter accepting an input signal, a transmission line for carrying a transmission signal, and a receiver receiving the transmission signal and developing an output signal.
In accordance with the invention, converter means in the transmitter develop a pulse width signal with a duration corresponding in a predetermined manner to the value of the input signal, and means in the transmitter provide the transmission signal (e.g., a current signal) with two states (e.g., opposite polarities), one of which has a duration corresponding to the duration of the pulse width signal. Means in the receiver provide the output signal with a duration corresponding to the duration of the one transmission signal state, which corresponds in turn to the value of the input signal, and can be used for conversion to digital or analog form. Means in one of the transmitter or receiver supplies power for the transmission signal, and means in the other of the transmitter or receiver derives operational power, e.g., for the telemetering instrument, from the transmission signal. The signal transmission system thus is able to convey signals with less susceptibility to noise, while at the same time retaining the ability to convey operational power.
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Citations
16 Claims
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1. A signal transmission system of the type used in process control systems for conveying a signal between a field instrument and a central controller, or between a central controller and a process control device, comprising:
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a transmitter arranged to accept an input signal; converter means in the transmitter for developing a pulse width signal with a duration corresponding in a predetermined manner to the value of the input signal; means in the transmitter for providing a transmission signal with two states, said means being responsive to the converter means to cause the duration of one of the transmission signal states to correspond to the duration of the pulse width signal; a transmission line for carrying the transmission signal; a receiver for receiving the transmission signal; means in the receiver for developing an output signal with a duration corresponding to the duration of the one transmission signal state, whereby the duration of the output signal corresponds in said predetermined manner to the value of the input signal; means, in one of the transmitter or receiver, for supplying power for the transmission signal; and means, in the other of the transmitter or receiver, for deriving operational power from the transmission signal; whereby the signal transmission system is able to convey signals less affected by noise, and is also able to convey operational power. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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Specification