Abstract:
An electromagnetic fluid flowmeter (26) includes empty pipe detection circuitry. The empty pipe detection circuitry applies a common mode asynchronous signal into a pair of electrodes (16A, 16B) in the flowmeter (26). Impedance of fluid is determined by measuring the magnitude of the asynchronous signal between an electrode (16A, 16B) and electrical ground. Impedance is used to determine an empty pipe condition.
Abstract:
A flowtube assembly (200) for a magnetic flowmeter (102) is provided. The flowtube assembly (200) includes a flowtube (202) configured to receive a flow of process fluid. A magnetic core (224) is mounted relative to the flowtube (202) and includes a plurality of layers (300) of a magnetically permeable material. Each layer (300) is substantially planar and is electrically insulated from others of the plurality of layers (300). A coil (216) is disposed to generate a magnetic field having field lines that are substantially orthogonal to the plane of each layer (300).
Abstract:
A process variable transmitter (10) includes a sensor drive controller (22) that outputs a sensor drive signal that is used to drive a sensor (22) that senses a process variable. The sensor drive controller (20) changes the frequency of the sensor drive signal to avoid frequencies and associated harmonics at which noise occurs and which could interfere with the sensor signal.
Abstract:
A current-to-pressure converter (50) sets line pressure to a desired pressure indicated by the current. A circuit (56) senses the line pressure and the current, receives compensation, and outputs a compensated difference between line and desired pressures. A first driver circuit (64) provides actuator drive based on the compensated output. The actuator (68) controls the line pressure, but presents a temperature sensitive, reactive load to the actuator drive. A simulated load (76) simulates a resistive part of the actuator load. A second driver (78) provides simulated drive to the simulated load. The second driver (78) generates the compensation which simulates actuator drive parameters, but is isolated from reactive effects and temperature sensitivity of the actuator (68).
Abstract:
A flowtube assembly (10) for a magnetic flowmeter is provided. The flowtube assembly (10) includes a tube (12) extending from a first mounting flange (14) to a second mounting flange (16). Each of the first and second mounting flanges (14,16) has a pipe flange facing surface (15, 17) for mounting to a respective pipe flange. A coil chamber (42) is disposed outside the tube (12), between the first and second mounting flanges (14,16). The coil chamber (42) has at least one coil (40) located inside that is configured to generate a magnetic field within the tube (12). A liner/electrode module (22) is positioned within the tube (12) and has a non- conductive liner, at least one electrode (50, 51) and at least one electrode conductor (76,78). The non-conductive liner extends from the first mounting flange (14) to the second mounting flange (16). The at least one electrode (50, 51) is positioned in the non-conductive liner to interact with a conductive process fluid. The electrode conductor (76,78) extends from the at least one electrode (50, 51) to an interconnect tab (24) disposed adjacent the pipe facing flange surface of one of the first and second mounting flanges (14,16). The liner/electrode module (22) is positionable within the tube (12).
Abstract:
A process control instrument (10) receiving a DC current from a two wire loop (11, 43) having overcurrent protection (16, 52) and reverse current protection (20, 54) circuits interposed between a two wire loop (11, 43) and a process control device (24) for reducing the incidence of damage or degradation to the process control device (24) from excessive and reverse polarity currents from the loop. The overcurrent protection circuit (16, 52) comprises device current flowing through a first current sensing circuit (34, 60) which generates a first output which controls impedance of a current diverting circuit (38, 62). The impedance of the current diverting circuit controls the flow of a shunt current shunted back to the two wire loop (11, 43). Shunt current flowing through a second current sensing circuit (13, 50) generates a second output which controls impedance of a first variable impedance circuit (32, 70). The first variable impedance circuit (32, 70) conducts the device current and limits device current flowing through the process control device (24) to a predetermined range. A potential sensing circuit (18, 94) in the reverse current protection circuit (20, 54) senses a potential induced across the process control device (24) and generates a third output which is indicative of polarity of device current. The third output controls impedance of a second variable impedance circuit (30, 56) which also conducts the device current. The second variable impedance circuit (30, 56) reduces the flow of reverse polarity current through the process control device (24) while having little effect on normal operation of the process control instrument (10).
Abstract:
A process variable transmitter includes a sensor drive controller that outputs a sensor drive signal that is used to drive a sensor that senses a process variable. The sensor drive controller changes the frequency of the sensor drive signal to avoid frequencies and associated harmonics at which noise occurs and which could interfere with the sensor signal.
Abstract:
A process control instrument (10) receiving a DC current from a two wire loop (11, 43) having overcurrent protection (16, 52) and reverse current protection (20, 54) circuits interposed between a two wire loop (11, 43) and a process control device (24) for reducing the incidence of damage or degradation to the process control device (24) from excessive and reverse polarity currents from the loop. The overcurrent protection circuit (16, 52) comprises device current flowing through a first current sensing circuit (34, 60) which generates a first output which controls impedance of a current diverting circuit (38, 62). The impedance of the current diverting circuit controls the flow of a shunt current shunted back to the two wire loop (11, 43). Shunt current flowing through a second current sensing circuit (13, 50) generates a second output which controls impedance of a first variable impedance circuit (32, 70). The first variable impedance circuit (32, 70) conducts the device current and limits device current flowing through the process control device (24) to a predetermined range. A potential sensing circuit (18, 94) in the reverse current protection circuit (20, 54) senses a potential induced across the process control device (24) and generates a third output which is indicative of polarity of device current. The third output controls impedance of a second variable impedance circuit (30, 56) which also conducts the device current. The second variable impedance circuit (30, 56) reduces the flow of reverse polarity current through the process control device (24) while having little effect on normal operation of the process control instrument (10).
Abstract:
A current-to-pressure converter (50) sets line pressure to a desired pressure indicated by the current. A circuit (56) senses the line pressure and the current, receives compensation, and outputs a compensated difference between line and desired pressures. A first driver circuit (64) provides actuator drive based on the compensated output. The actuator (68) controls the line pressure, but presents a temperature sensitive, reactive load to the actuator drive. A simulated load (76) simulates a resistive part of the actuator load. A second driver (78) provides simulated drive to the simulated load. The second driver (78) generates the compensation which simulates actuator drive parameters, but is isolated from reactive effects and temperature sensitivity of the actuator (68).
Abstract:
Un convertisseur (50) courant/pression établit une pression voulue, indiquée par le courant, dans un conduit. Un circuit (56) détecte la pression dans le conduit et le courant, reçoit une compensation et produit une différence compensée entre la pression voulue et la pression dans la ligne. Un premier circuit d'entraînement (64) assure l'entraînement de l'organe d'actionnement sur la base de la sortie compensée. L'organe d'actionnement (68) règle la pression dans le conduit mais renvoie une charge thermosensible de réaction au circuit d'entraînement de l'organe d'actionnement. Une charge simulée (76) simule une partie de résistance de la charge de l'organe d'actionnement. Un deuxième circuit d'entraînement (78) assure un entraînement simulé de la charge simulée. Le deuxième circuit d'entraînement (78) génère une composition qui simule des paramètres d'entraînement de l'organe d'actionnement mais est isolé par rapport aux effects de réaction et à la sensibilité thermique de l'organe d'actionnement (68).