Abstract: A communications protocol operable in a multi-processor transmitter environment that facilitates communication between the microprocessors is provided. The transmitter includes a sensor module having a sensor microprocessor and a sensor memory. The sensor module digitizes and compensates sensed process variables. The transmitter also includes an electronics module having an electronics microprocessor wherein the sensor and electronics microprocessors each include individually controllable output pins and individually readable input pins. The sensor and electronics microprocessors are connected by an interface having a bus system. The communications protocol comprises a set of instructions formed into procedures. The procedures include a sensor update procedure; a receive data procedure; a send data procedure; a send command procedure; an indexed read procedure; and a read memory direct procedure.

Abstract: In this invention, a multivariable transmitter providing an output representative of mass flow has a dual microprocessor structure. The first microprocessor compensates digitized process variables and the second microprocessor computes the mass flow as well as arbitrating communications between the transmitter and a master. In a second embodiment of the present invention, a first microprocessor compensates digitized process variables, a second microprocessor computes an installation specific physical parameter such as mass flow and a third microprocessor arbitrates real-time communications between the transmitter and a master.

Abstract: An improved error detection for microprocessor-based transmitters in two-wire process control loops operating in the process control industry. In particular, techniques are shown which are useful in solving malfunctions or failures of microprocessor-based transmitters. When the transmitter is energized, the impedance of the process loop cabling is resolved and stored, displayed or transmitted as desired. The loop impedance is used to calculate potential of a power supply used to power the control loop. This information is used in testing the two-wire loop.

Abstract: A smart field-mounted control unit, for controlling a process, receives signals and sends a command output over a two-wire circuit which powers the control unit. An input section receives the signal, which can be instructions representative of commands or instructions sets, process variables sensed by external control units or setpoints representative of a desired process state. The instructions are representative of a control requirement of the process and adjust a controlling section in the control unit to generate the command output in conformance with the control requirement. The command output can be a function of the difference between the process setpoint and a process variable, or a function of a linear combination of a process variable and its calculated time integral and time derivative functions.

Abstract: An elevator system having a plurality of cars under group supervisory control by a programmable dispatcher. A monitor detects dispatcher failure via a plurality of tests which includes timing each hall call, and performing predetermined checks, tests and comparisons for each call related to actual system operating conditions.