Abstract:
A temperature transmitter (10) in a process control system includes a temperature sensor (16, 18) which senses temperature and provides a sensor output related to sensed temperature. An analog-to-digital converter (28) coupled to the sensor output provides a digitized output related to the sensor output. A microprocessor (22) receives the digitized output, compensates the digitized output and provides a temperature output. Comparison circuitry (12) compares the sensor output to a first threshold VREF1 and provides an inhibit signal to the microprocessor (22) if the sensor is outside of the first threshold VREF1.
Abstract:
A transmitter (10) in a process control loop (12) measures temperature. A calibrator (60) includes a known calibration element (64) which is connected to the transmitter (10). Software in the transmitter (10) compares a measured value of the calibration element (64) with the actual value of the calibration element (64) and responsively calibrates the transmitter (10). The calibrator (60) includes a temperature calibration sensor (70) for coupling to a terminal block (14) of the transmitter (10). The temperature calibration sensor (70) provides an actual temperature input to the transmitter (10). The transmitter (10) measures actual temperature of the terminal block (14) and compares actual temperature with a temperature measured by an internal terminal block temperature sensor (34), and responsively calibrates the internal temperature sensor (34).
Abstract:
A transmitter (100) transmitting a sensed process variable over a conductor (134A, 134B) includes a cylindrical housing (102) having a terminal compartment (110) and an electronics compartment (108) separated by a bulkhead (106). The terminal compartment (110) used for conductor connection is subject to moisture accumulation. An access channel (136) fully intersects an internal surface of terminal compartment (110) such that the access channel (136) drains moisture from the terminal compartment (110) across a range of mounting orientations. The transmitter (100) includes a circuit (104) in the electronics compartment (108) for compensating a process variable and providing the compensated process variable via a feedthrough circuit assembly (142) in the bulkhead (106), which in one embodiment, includes an encapsulated radio frequency interference filter (144), to terminals (132A, 132B) in the terminal compartment (110) for coupling to a conductor (134A, 134B) that is connected to an external controller.
Abstract:
A process transmitter (50) transmits a 4-20 mA current representing a sensed parameter to a loop (52) which energizes the transmitter (50). An output circuit (60) receives energization from the loop (52) and controls the 4-20 mA output as a function of a sensor data input. The output circuit (60) further generates a transformer driver output which also serves as a clock for isolated circuitry (106). A sensor circuit (82) generates a transformer driver output representing the sensed parameter. An isolation transformer (76) driven by the driver output excites the sensor circuit (82) and provides a clock reference as a function of the driver output oscillation to the sensor circuit (82) . The isolation transformer (76) is a single coupling device which couples energization, clock reference, sensor data and programming data across an electrically insulating barrier between the output circuit (50) and the sensor circuit (82).
Abstract:
A temperature transmitter (10) in a process control system includes a temperature sensor (16, 18) which senses temperature and provides a sensor output related to sensed temperature. An analog-to-digital converter (28) coupled to the sensor output provides a digitized output related to the sensor output. A microprocessor (22) receives the digitized output, compensates the digitized output and provides a temperature output. Comparison circuitry (12) compares the sensor output to a first threshold VREF1 and provides an inhibit signal to the microprocessor (22) if the sensor is outside of the first threshold VREF1.
Abstract:
A two-wire temperature transmitter (12, 40, 50) performs thermocouple diagnostics on a thermocouple (32) attached to the transmitter (12, 40, 50) to determine if, and the extent to which, the thermocouple (32) has degraded. Various methods (60) of obtaining thermocouple resistance are also provided.
Abstract:
A two-wire field-mounted process device (16) with multiple isolated channels includes a channel that can be an input channel or an output channel. The given input or output channel can be coupled to multiple sensors or actuators (32, 34), respectively. The process device (16) is wholly powered by the two-wire process control loop (14). The process device (16) includes a controller (40) adapted to measure one or more characteristics of sensors (20, 22, 24, 26, 28, 30) coupled to an input channel (42, 44, 46) and to control actuators coupled to an output channel (48). The controller can be further adapted to execute a user generated control algorithm relating process input information with process output commands. The process device also includes a loop communicator (36) that is adapted to communicate over the two-wire loop.
Abstract:
Un émetteur de traitement (50) transmet un courant de 4 à 20 mA représentant un paramètre détecté à une boucle (52), laquelle excite l'émetteur (50). Un circuit de sortie (50) reçoit l'excitation provenant de la boucle (52) et régule la sortie de 4 à 20 mA en fonction d'une entrée de données de détecteur. Le circuit de sortie (60) produit également une sortie de commande de transformateur, laquelle sert aussi d'horloge pour le circuit isolé (106). Un circuit détecteur (82) produit une sortie de commande de transformateur représentant le paramètre détecté. Un transformateur d'isolement (76) commandé par la sortie de commande excite le circuit détecteur (82) et produit une référence d'horloge en fonction de l'oscillation de la sortie de commande jusqu'au circuit détecteur (82). Le transformateur d'isolement (76) est un dispositif à couplage unique couplant l'excitation, la référence d'horloge, des données de détecteur ainsi que des données de programmation sur une barrière d'isolement électrique située entre le circuit de sortie (50) et le circuit détecteur (82).
Abstract:
A two-wire field-mounted process device (16) with multiple isolated channels includes a channel that can be an input channel or an output channel. The given input or output channel can be coupled to multiple sensors or actuators (32, 34), respectively. The process device (16) is wholly powered by the two-wire process control loop (14). The process device (16) includes a controller (40) adapted to measure one or more characteristics of sensors (20, 22, 24, 26, 28, 30) coupled to an input channel (42, 44, 46) and to control actuators coupled to an output channel (48). The controller can be further adapted to execute a user generated control algorithm relating process input information with process output commands. The process device also includes a loop communicator (36) that is adapted to communicate over the two-wire loop.