Dynamically adjusted A/D resolution
First Claim
1. A method of controlling an analog-to-digital (A/D) converter in a process variable transmitter that converts an analog input signal indicative of an industrial process variable to a digital output signal, the method comprising:
- receiving the analog input signal indicative of the industrial process variable;
performing a first measurement measuring a signal level of the analog input signal using the A/D converter, wherein a resolution of the A/D converter changes as the measured signal level of the analog input signal varies;
introducing a signal offset into the signal level of the analog input signal to move the measured signal level to increase the resolution of the A/D converter;
performing a second measurement measuring the signal level of the analog input signal with the offset;
converting the analog input signal, measured using the second measurement, to the digital output signal; and
sending information, using the converted signal, related to the industrial process variable over a transmission connection.
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Abstract
A process variable transmitter is used to measure a process variable, and, in doing so, dynamically changes the resolution of the A/D converter based upon the measured value of the analog input signal. This can be done by automatically adjusting the configurable resolution gain adjustment based on the value of the analog signal being measured, by normalizing the input signal being measured so that it is centered in an optimal resolution window of the A/D converter, or by adjusting a voltage reference provided to the A/D converter.
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Citations
20 Claims
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1. A method of controlling an analog-to-digital (A/D) converter in a process variable transmitter that converts an analog input signal indicative of an industrial process variable to a digital output signal, the method comprising:
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receiving the analog input signal indicative of the industrial process variable; performing a first measurement measuring a signal level of the analog input signal using the A/D converter, wherein a resolution of the A/D converter changes as the measured signal level of the analog input signal varies; introducing a signal offset into the signal level of the analog input signal to move the measured signal level to increase the resolution of the A/D converter; performing a second measurement measuring the signal level of the analog input signal with the offset; converting the analog input signal, measured using the second measurement, to the digital output signal; and sending information, using the converted signal, related to the industrial process variable over a transmission connection. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of controlling an analog-to-digital (A/D) converter in a process variable transmitter that converts an analog input signal indicative of an industrial process variable to a digital output signal, the method comprising:
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receiving the analog input signal indicative of the industrial process variable; performing a first measurement measuring a signal level of the analog input signal using the A/D converter, wherein a resolution of the A/D converter changes as the measured signal level of the analog input signal varies among a plurality of different signal ranges; if the measured signal level of the analog input signal is in a lower resolution range of the plurality of different signal ranges, introducing a signal offset into the signal level of the analog input signal to move the measured signal level into a higher resolution range of the plurality of different signal ranges; performing a second measurement measuring the signal level of the analog input signal with the offset; converting the analog input signal to the digital output signal using the higher resolution range; and sending information, using the converted signal, related to the industrial process variable over a transmission connection. - View Dependent Claims (11, 12, 13, 14, 15)
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16. A process variable transmitter that receives a sensor input signal from a sensor that senses a process variable and provides the sensor input signal at an analog signal level indicative of the process variable, comprising:
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an analog-to-digital (A/D) converter that converts the sensor input signal to a digital value at a resolution, wherein the resolution obtainable by the A/D converter changes according to a predetermined relationship between the analog signal level of the sensor input signal and a reference voltage provided to the A/D converter; an input signal normalizer that introduces an offset into the sensor input signal; and a processor, coupled to the A/D converter, receiving the digital value and transmitting information over a process control loop based on the digital value, the processor providing a resolution control signal to the input signal normalizer to introduce the offset into the sensor input signal so the A/D converter provides the digital value at a given resolution. - View Dependent Claims (17, 18, 19, 20)
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Specification