Abstract: A method and apparatus for detecting and clearing a plugged sensor port in a system containing a fluid being monitored through the sensor port. The method comprises establishing a range beyond which a fluid variable is expected to vary within a predetermined time interval, measuring the fluid variable, and indicating a plugged sensor port in response to the measured fluid variable remaining within the range for the predetermined time interval. The apparatus includes a sensor mechanism that senses a fluid variable, and a controller. The controller establishes the range beyond which the fluid variable is expected to vary within a predetermined time interval, determines whether the fluid variable is within the range, and indicates a plugged sensor port in response to the fluid variable remaining within the range for the predetermined time interval. The apparatus may further include a mechanism that clears the plugged sensor port.

Abstract: A method and apparatus for detecting and clearing a plugged sensor port in a system containing a fluid being monitored through the sensor port. The method comprises establishing a range beyond which a fluid variable is expected to vary within a predetermined time interval, measuring the fluid variable, and indicating a plugged sensor port in response to the measured fluid variable remaining within the range for the predetermined time interval. The apparatus includes a sensor mechanism that senses a fluid variable, and a controller. The controller establishes the range beyond which the fluid variable is expected to vary within a predetermined time interval, determines whether the fluid variable is within the range, and indicates a plugged sensor port in response to the fluid variable remaining within the range for the predetermined time interval. The apparatus may further include a mechanism that clears the plugged sensor port.

Abstract: An interface that provides selected information from a remote device to a utilization mechanism over a two-wire connection, wherein all power for the interface and the remote device is received from the utilization mechanism over the same two-wire connection. A switch circuit provides a high impedance between first and second wires of the two-wire connection when open and a low impedance between the wires when closed. Current flow through the switch circuit is sensed by the utilization mechanism as indicative of information from the remote device. The interface comprises a voltage regulator that provides a regulated voltage to components of the interface and the remote device, and a current regulator that regulates current provided to the voltage regulator from the two-wire connection, when the switch circuit is open, to below a predetermined level at which the utilization mechanism interprets the switch circuit as being in the open state.

Abstract: A sensor device is provided for sensing a selected parameter such as pressure or temperature at a selected site, which is typically a remote site, and for generating outputs, normally to a control site, which outputs are either selected steady state or non-steady state outputs, the non-steady state outputs being indicative of the parameter being within a normal or acceptable range and/or the parameter being within an unacceptable or alarm range. The steady state outputs can be indicative either of the parameter being within a normal range or of a device failure. A particular steady state output, for example a null output, may be indicative of all failure conditions or different steady state outputs may be utilized to indicate different failure conditions.