Field device power supply failure detection

A method of operating a field device for monitoring a manufacturing process and/or for actuating manufacturing process variables, the method comprising:

• continuously monitoring a voltage on a control bus connecting the field device with a central controller or an operating current flowing from the control bus into the field device, where the control bus includes a two-wire interface that provides an operating current supplying both a power signal for powering the field device and a communications signal for directing an operation of the field device;
• generating a power supply interrupt signal when the monitored voltage/operating current decreases beyond a predetermined first threshold (UB,min);
• routing the power supply interrupt signal to a field device controller so as to circumvent an effective capacitance of the field device, such that a decrease in power being supplied by the control bus is detected at the field device controller without being substantially affected by a delay associated with the effective capacitance;
• and
• saving internal states in an internal memory of a field device controller after supplying the power supply interrupt signal to the field device controller.

A computer program product directly loadable into a memory of a field device controller, the product including software code for causing the field device to monitor a manufacturing process and/or to actuate manufacturing process variables, by causing the field device controller to:

• continuously monitor a voltage on a control bus connecting the field device with a central controller or an operating current flowing from the control bus into the field device, where the control bus includes formed by a two-wire interface that provides an operating current supplying both a power signal for powering the field device and a communications signal for directing an operation of the field device;
• generate a power supply interrupt signal when the monitored voltage/operating current decreases beyond a predetermined first threshold (UB,min);
• route the power supply interrupt signal to a field device controller so as to circumvent an effective capacitance of the field device, such that a decrease in power being supplied by the control bus is detected at the field device controller without being substantially affected by a delay associated with the effective capacitance;
• and
• save internal states in an internal memory of a field device controller after supplying the power supply interrupt signal to the field device controller.