Control system methods and apparatus for inductive communication across an isolation barrier
AssigneeInvensys Systems, Inc.
InventorJames G. Calvin
Life of this patent
Estimating the term…
Abstract
Improved control apparatus and methods transfer information between devices, such as controllers and field devices, utilizing a modulator that generates a pulse width modulated (PWM) signal containing information to be transferred by a first of the devices, e.g., the controller, to the second device. A transformer or other inductive device transfers the PWM signal across the isolation barrier, where it is demodulated to analog form for application to the second device, e.g., the field device. Information transferred from the second device to the first device can be transferred in an amplitude modulated (AM) signal that utilizes, as its carrier, a fixed duty cycle output of the modulator that generates the PWM signal.
Claims52
An input/output circuit of a process control system, comprising:
- a transformer that generates an analog frequency shift keying (FSK) signal for transfer across an isolation barrier, the FSK signal being transferred by the transformer and encoded in a pulse width modulated (PWM) signal, the PWM signal comprising pulses whose widths are based on the FSK signal.
An isolation logic circuit for use in transferring information over a transformer between first and second control devices, the isolation logic comprising
- a modulator that generates a pulse width modulated (PWM) signal encoding an analog frequency shift keying (FSK) signal to be transferred between the first and second control devices, the PWM signal comprising pulses whose widths are based on the FSK signal, and
- the modulator being coupled to the transformer and applying the PWM signal thereto.
An input/output module for use in any of industrial, manufacturing, service, environmental, or process control to transfer information over an isolation barrier between first and second control devices, the module comprising
- transformer logic that inductively transfers a pulse width modulated (PWM) signal across the isolation barrier from the first to the second control device, the PWM signal being a converted analog frequency shift keying (FSK) signal, and
- the transformer logic inductively transferring an amplitude modulated (AM) signal across the isolation barrier, the AM signal having encoded therein another analog FSK signal being transferred from the second to the first control device.
A control system comprising,
- a first control device and a second control device, each of the first and second control devices including any of a workstation, field controller, field device, smart field device, or other device for any of industrial, manufacturing, service, environmental, or process control,
- a first analog source that generates a first analog frequency shift keying (FSK) signal encoding information for transfer from the first control device to the second control device,
- a first modulator that is coupled to the first analog source, the first modulator generating a pulse width modulated (PWM) signal having encoded therein the first FSK signal, the PWM signal comprising pulses whose widths are based on the first FSK signal,
- a second analog source that generates a second analog FSK signal encoding information for transfer from the second control device to the first control device,
- a second modulator that is coupled to the second analog source, the second modulator generating an amplitude modulated (AM) signal having encoded therein the second FSK signal, and
- first and second transformers that are coupled to the first and second modulators, respectively, the first and second transformers inductively carrying the PWM and AM signals, respectively, across an isolation barrier.
In a method of operating a process control system of the type having a transformer that transfers an analog frequency shift keying (FSK) signal across an isolation barrier, the improvement comprising encoding the FSK signal to be transferred by the transformer in a pulse width modulated (PWM) signal, the PWM signal comprising pulses whose widths are based on the FSK signal.
A method of transferring an analog frequency shift keying (FSK) signal over a transformer between first and second control devices, the method comprising the steps of
- generating a pulse width modulated (PWM) signal to be transferred between the first and second control devices by converting the FSK signal to the PWM signal, and
- applying the PWM signal to the transformer for transfer between the first and second control devices.
A method for use in any of industrial, manufacturing, service, environmental, or process control for transferring information over an isolation barrier between first and second control devices, the method comprising
- inductively transferring a pulse width modulated (PWM) signal across the isolation barrier, the PWM signal having encoded therein an analog frequency shift keying (FSK) signal containing information being transferred from the first to the second control device, the PWM signal comprising pulses whose widths are based on the FSK signal, and
- inductively transferring an amplitude modulated (AM) signal across the isolation barrier, the AM signal having encoded therein another analog FSK signal containing information being transferred from the second to the first control device.
A method of operating a control system comprising,
- generating a first analog frequency shift keying (FSK) signal encoding information for transfer from a first control device to a second control device, each of the first and second control devices including any of a workstation, field controller, field device, smart field device, or other device for any of industrial, manufacturing, service, environmental, or process control,
- generating a pulse width modulated (PWM) signal by converting the first FSK signal to the PWM signal,
- generating a second FSK signal encoding information for transfer from the second control device to the first control device,
- generating an amplitude modulated (AM) signal having encoded therein the second FSK signal, and
- inductively transferring the PWM and AM signals across an isolation barrier.
Dependencies are inferred from the claim text.