Sensor conditioning method and apparatus

A method for obtaining a linearized output from a sensor, where the sensor normally has an output that is a nonlinear function of the physical quantity being measured, comprising the steps of:

• calibrating the sensor by building a changeable look-up table for a plurality of conditions of the physical quantity in which the sensor signals correspond to linearized reference values, including the substeps of
• measuring the physical quantity in a plurality of conditions with both the sensor and a reference transducer that outputs a reference value that is a linear function of the physical quantity being measured,
• outputting for each condition a sensor signal and a reference value to establish a changeable look-up table with a unique reference value for each condition measured;
• operating the sensor to obtain a linearized output corresponding to the physical quantity in an unknown condition including the substeps of
• measuring the physical quantity in the unknown condition with the sensor to produce a sensor signal, adjusting the sensor signal for gain and offset in real time,
• outputting the adjusted sensor signal to the look-up table,
• entering the look-up table with the adjusted sensor signal,
• determining a reference value that corresponds to the adjusted sensor signal and is a linear function of the physical quantity being measured, and
• outputting the reference value from the look-up table as the linearized output corresponding to the physical quantity in the unknown condition.

An apparatus to adjust the output of a sensor which produces an undesirable output signal in relation to changes in condition of a physical quantity being measured by the sensor, comprising:

• reference means coupled to the physical quantity for producing an output which varies in a desirable fashion with changes in the condition of the physical quantity;
• microprocessor means having a changeable look-up table for receiving the values of the sensor signals and reference means outputs, and for matching the values of the signals and outputs by adjusting the sensor output by providing realtime feedback signals to obtain an adjusted sensor output for a given physical quantity condition, including
• means for receiving an adjusted sensor signal indicative of the physical quantity in an unknown condition for determining a reference value from the look-up table using only the adjusted sensor signal of the unknown condition as the input;
• and
• means coupled to the microprocessor means for indicating the reference value.

A method of providing a measurement output which varies linearly with changes in a physical quantity being measured using a sensor having an output which varies nonlinearly with changes in the physical quantity being measured, comprising the steps of:

• measuring the physical quantity in a plurality of conditions with the nonlinear sensor and with a linear transducer having an output which varies linearly with changes in the physical quantity being measured;
• outputting a nonlinear sensor signal adjusted in real time for gain and offset and a linear transducer value for each condition measured to build a look-up table matching a linear transducer value with a nonlinear sensor signal for each condition measured;
• measuring the physical quantity in an unknown condition with the nonlinear sensor to produce an object sensor signal;
• comparing the object sensor signal with the look-up table sensor signals to identify a look-up table location;
• retrieving the linear transducer value from the identified look-up table location;
• and
• outputting a measurement of the physical quantity in the unknown condition using said identified linear transducer value.