Apparatus and method for compensated sensor output

#The present disclosure relates to the field of physical sensing and, more particularly, to the correction of sensor errors due to such factors as nonlinear sensor response and temperature effects, for example.

#Control systems operate with electrical signals that represent pressure, force, flow rate, or other sensed physical parameter. The physical parameter must be converted to a current or voltage signal before further processing or analysis by the control system. For example, capacitive and resistive sensors are often used for measuring pressure, and resistive “bridges” are used to measure mass flow. Unfortunately, such sensors typically exhibit nonlinear behavior and temperature dependencies. For example, a pressure sensor may provide a given voltage swing for a given pressure change at a specified temperature and pressure range, but a different voltage swing for the same pressure change over a different pressure range. Or the sensor may provide a different voltage swing for the same pressure change at the same pressure range, but at a different temperature.

#Although sensor compensation techniques for such sensor inadequacies as temperature and/or nonlinearity effects are known, they tend to be time consuming and/or costly. A method and apparatus for the compensation of such deficiencies that provides a rapid response, precise compensation, at a relatively low cost would be highly desirable.

#The foregoing and other features and advantages of this disclosure will be better understood from the detailed description and the drawings, in which:

#FIG. 1 is a conceptual block diagram of a compensated sensor in accordance with the principles of the present invention;

#FIG. 2 is a flow chart that describes a sensor compensation process in accordance with the principles of the present invention;

#The block diagram of FIG. 1 provides an overview of a compensated sensor 100 in accordance with the principles of the present invention. The compensated sensor 100 includes a relatively fast feedthrough path 102 and a somewhat slower but more precise compensation path 104. The feedthrough 102 and compensation 104 paths are united by a summer 106. A sensor 108 provides a signal that is responsive to a physical phenomenon, such as pressure or mass flow, for example. The uncompensated sensor signal, S, output from the sensor 108 is fed along the feedthrough path 102 to the summer 106, which responds nearly instantaneously by producing an output SA.

#The uncompensated sensor signal, S, is also fed along the compensation path 104 to a compensator 110. In a correction block 109, the compensator 110 produces one or more compensation values, C1-Cn, which may be combined within the compensator 110, then provided to the summer 106, or provided to the summer 106 separately. The compensation values C1-Cn may compensate for sensor nonlinearity, temperature effects, or other sensor deficiencies. The compensator 110 either includes or has access to information necessary for compensating the sensor errors. That is, for example, the compensator 110 includes an input that provides access to, or includes circuitry that determines, the current temperature of a sensor that is being compensated for temperature effects.

#The feedthrough path 102 includes an output amplifier 112. As is known in the art, the summer 106 may be incorporated with the output amplifier 112 to form a summing amplifier. The output amplifier 112 produces a compensated sensor output: analog signal, A. That is, as the sum of one or more correction factors produced by the compensator 110, and the uncompensated sensor signal S, the analog output A of the amplifier 112 is the compensated sensor output. In addition to being available for use by external circuitry, the output A, properly scaled if necessary, is fed back to the compensator 110, where it is compared in a difference circuit 111 to a compensated signal of the form (S+C1), where S is the uncompensated sensor output and C1 is one or more correction factors that compensate for temperature, nonlinearity, or other sensor defects. The difference, D, between the output signal A and the compensated signal (S+C1) is fed to the summer 106. After a settling period, during quiescent operation, the output signal A and the compensated signal S+C1 are equal. During a transient, however, the slower compensator 110 will not update as quickly as the feedthrough path 102. Consequently, during a transient period, the output A will be the sum of an updated, uncompensated sensor signal St1 and an older correction factor Ct0 (which may include a plurality of correction factors C1-Cn and a difference signal D). After a delay, the compensator produces a correction factor Ct1 that corresponds to the updated sensor output St1; this updated correction factor is then added to the sensor output St1 in the summer 106. The compensated signal, S+C1, may also be made available as an output 113 to other circuitry.