Power supply for field mounted transmitter
First Claim
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1. A transmitter for use in a two-wire process control loop, comprising:
- a sensor which senses a process variable and provides an output signal representative of the process variable;
measurement circuitry coupled to the sensor to receive the output signal, the measurement circuitry transmitting a signal over the two-wire process control loop indicative of a value of the process variable;
power supply circuitry coupled to the measurement circuitry, the power supply circuitry receiving a loop current from the two-wire process control loop and providing an energizing current to the measurement circuitry, the power supply circuitry comprising;
an inductive element coupled to the measurement circuitry; and
a switch selectively electrically connecting the inductive element to the two-wire process control loop to receive current from the two-wire process control loop;
a capacitor for storing charge;
modulation circuitry coupled to the measurement circuitry and the two-wire process control loop which responsively controls current through the two-wire process control loop; and
startup circuitry coupled to the modulation circuitry which controls the modulation circuitry to cause an increase in control loop current during a startup condition whereby the capacitor in the power supply circuit is charged.
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Abstract
A field mounted transmitter for use in a two-wire process control loop includes a sensor, measurement circuitry and a power supply. The sensor senses a process variable of a process which is transmitted over the control loop by the measurement circuitry. The power supply is powered by a current flowing through the control loop and powers the measurement circuitry. The power supply includes an inductive element coupled to the measurement circuitry and a switch which selectively couples the inductive element to the control loop.
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Citations
9 Claims
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1. A transmitter for use in a two-wire process control loop, comprising:
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a sensor which senses a process variable and provides an output signal representative of the process variable; measurement circuitry coupled to the sensor to receive the output signal, the measurement circuitry transmitting a signal over the two-wire process control loop indicative of a value of the process variable; power supply circuitry coupled to the measurement circuitry, the power supply circuitry receiving a loop current from the two-wire process control loop and providing an energizing current to the measurement circuitry, the power supply circuitry comprising; an inductive element coupled to the measurement circuitry; and a switch selectively electrically connecting the inductive element to the two-wire process control loop to receive current from the two-wire process control loop; a capacitor for storing charge; modulation circuitry coupled to the measurement circuitry and the two-wire process control loop which responsively controls current through the two-wire process control loop; and startup circuitry coupled to the modulation circuitry which controls the modulation circuitry to cause an increase in control loop current during a startup condition whereby the capacitor in the power supply circuit is charged. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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Specification