US 6,032,109 A · Smart sensor module

Abstract

A smart sensor module includes a microcontroller and a signal conditioning integrated circuit. In a preferred embodiment, the signal conditioning integrated circuit is a mixed signal application specific integrated circuit (ASIC) incorporating an instrumentation amplifier, offset correction, sensitivity correction, low pass filtering, an analog-to-digital converter (ADC), a temperature sensor, digital I/O interface, a crystal oscillator circuit, and power on reset open collector output. The ADC can be multiplexed to the transducer, the temperature sensor or an external input. All features of the ASIC can be dynamically reconfigured at any time by the microcontroller. Offset correction is implemented with a 4-bit coarse adjustment digital-to-analog converter (DAC) and a 7-bit fine adjustment DAC to control the instrumentation amplifier reference voltage. The coarse adjustment allows compensation of sensor-to-sensor offset variations, while the fine adjustment allows dynamic or real-time compensation of temperature-induced variations. The sensitivity correction is accomplished with a programmable system gain configured as a coarse gain adjustment and a fine gain adjustment. The coarse gain adjustment allows compensation of sensor-to-sensor sensitivity variations. The fine gain adjustment allows dynamic or real-time compensation of temperature-induced sensitivity variations. The smart sensor module allows very precise calibration of the sensor, signal processing capabilities, decision making capability and serial interface capability.

Claims20

Dependent claims

A smart sensor module for compensation of sensor-to-sensor and temperature-induced errors in the analog output of a sensor comprising

a temperature sensor providing an electrical output related to the temperature of the sensor;
fine gain and offset correction storage for storing fine gain and offset corrections for a plurality of different temperatures and, responsive to said temperature sensor output, for providing a fine gain correction output and a fine offset correction output;
coarse gain and offset correction storage for storing coarse gain and offset corrections and providing a coarse gain correction output and a coarse offset correction output;
an analog amplifier, having a DC offset responsive to said coarse and fine offset correction outputs, for amplifying the analog sensor output and providing an amplified analog sensor output;
a first low pass filter, having a filter gain responsive to said coarse gain correction output, for low pass filtering the amplified analog sensor output and providing a coarse gain corrected analog sensor output;
and
a second low pass filter, having a filter gain responsive to said fine gain correction output, for low pass filtering the coarse gain corrected analog sensor output and providing a fully conditioned analog sensor output.

4 more elements

A signal conditioning circuit for use with a microcontroller as a smart interface for an analog output sensor comprising

coarse offset adjustment means, responsive to digital input from the microcontroller, for providing an analog coarse offset correction output to correct for offset errors due to sensor-to-sensor variations;
fine offset adjustment means, responsive to digital input from the microcontroller, for providing an analog fine offset correction output to correct for offset errors due to temperature-induced variations;
an amplifier stage, having a DC offset responsive to said fine and coarse offset correction outputs, for amplifying the analog sensor output and providing an amplified analog sensor output;
coarse gain adjustment means, responsive to digital input from the microcontroller, for providing an analog coarse gain correction output to correct for sensor-to-sensor variations;
a first low pass filter stage, having a filter gain responsive to said coarse gain correction output, for filtering the amplified analog sensor output and providing a coarse gain corrected analog sensor output;
fine gain adjustment means, responsive to digital input from the microcontroller, for providing an analog fine gain correction output to correct for temperature-induced variations;
and
a second low pass filter stage, having a filter gain responsive to said fine gain correction output, for filtering the coarse gain corrected analog sensor output and providing a fully compensated analog sensor output.

5 more elements

A method of compensating for sensor-to-sensor and temperature-induced errors in an analog sensor output using a microcontroller and signal conditioning analog circuitry comprising the steps of

taking a temperature sample;
retrieving fine gain and offset correction outputs from storage based upon the temperature sample;
retrieving coarse gain and offset correction outputs from storage;
amplifying the analog sensor output in an amplifier stage of the signal conditioning analog circuitry having a DC offset responsive to the coarse and fine offset outputs retrieved from storage and providing an amplified analog sensor output;
filtering the amplified analog sensor output in a first low pass filter stage of the signal conditioning analog circuitry having a filter gain responsive to the coarse gain correction output retrieved from storage and providing a coarse gain corrected analog sensor output;
and
filtering the coarse gain corrected analog sensor output in a second low pass filter stage of the signal conditioning analog circuitry having a filter gain responsive to the fine gain correction output retrieved from storage and providing a fully compensated analog sensor output.

4 more elements

Dependencies are inferred from the claim text.

Smart sensor module

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Smart sensor module

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Abstract

Claims20