Process variable transmitter with EMF detection and correction
First Claim
Patent Images
1. A process variable transmitter, comprising:
- an analog-to-digital (A/D) converter that receives a sensor signal from a sensor indicative of a sensed process variable, the sensor being controllable to receive a control signal and output the sensor signal in response to the control signal, the A/D converter converting the sensor signal into a digital signal;
a processor, that provides the control signal to the sensor and that receives the digital signal and provides a measurement output indicative of the digital signal; and
a detection component receiving a preexisting input from the sensor, prior to the processor providing the control signal to the sensor, and providing a detection signal to the processor indicative of a level of the preexisting input.
1 Assignment
0 Petitions
Accused Products
Abstract
A preexisting voltage across a sensor is latched to a storage capacitor prior to any excitation current being applied to the sensor. Once the excitation current is applied, the voltage on the storage capacitor is directly subtracted from a differential voltage across the sensor. The subtraction is done before a measurement is converted to a digital value and passed to a transmitter. The subtraction is performed in hardware, and a time required to sample and hold the preexisting voltage across the storage capacitor is within a settling time used for collecting any sensor measurements.
-
Citations
22 Claims
-
1. A process variable transmitter, comprising:
-
an analog-to-digital (A/D) converter that receives a sensor signal from a sensor indicative of a sensed process variable, the sensor being controllable to receive a control signal and output the sensor signal in response to the control signal, the A/D converter converting the sensor signal into a digital signal; a processor, that provides the control signal to the sensor and that receives the digital signal and provides a measurement output indicative of the digital signal; and a detection component receiving a preexisting input from the sensor, prior to the processor providing the control signal to the sensor, and providing a detection signal to the processor indicative of a level of the preexisting input. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
-
-
17. A method of sensing a process variable in a process control system, the method comprising:
-
providing a control signal to a sensor to obtain, at a sensor input, a sensor signal from the sensor indicative of the process variable; converting the sensor signal from an analog signal to a digital signal; providing an output on a process control loop indicative of the digital signal; prior to providing the control signal, detecting a preexisting signal level at the sensor input; and after providing the control signal, compensating the sensor signal for the preexisting signal level before converting the sensor signal to the digital signal. - View Dependent Claims (18, 19, 20)
-
-
21. A process control system, comprising:
-
a sensor that senses a process variable and provides an analog sensor signal indicative of the sensed process variable, the sensor being controllable to receive a control signal and output the analog sensor signal in response to the control signal; a process variable transmitter comprising; an analog-to-digital (A/D) converter that receives, at a sensor input, the analog sensor signal from the sensor, the A/D converter converting the sensor signal into a digital signal; a processor, coupled to the A/D converter, that provides the control signal to the sensor and that receives the digital signal and provides a measurement output indicative of the digital signal; and a detection component detecting a preexisting signal level, at the sensor input, prior to the controller providing the control signal to the sensor, and providing a detection signal to the processor indicative of a level of the preexisting input, the detector compensating the analog sensor signal for the preexisting signal level after the processor provides the control signal to the sensor; and a control loop, the processor providing the measurement output on the control loop. - View Dependent Claims (22)
-
Specification