US 5,764,541 A · Microprocessor controlled sensor signal conditioning circuit

Abstract

A method and apparatus for measurement signal compensation comprises providing an analog-to-digital converter that includes a dual slope integrator. A microprocessor controls the reference voltage applied to the integrator. An amplifier having a switchable gain, controls the amplification of the input signal to the integrator during the various phases of integration. An off-set compensation value is stored in a memory device for providing off-set compensation by charging a capacitor connected to the integrator. A full-scale rough adjust value is also stored on the memory device and is used as a specific reference to produce a reference voltage that is, in turn, used in the integrator during the negative slope phase. During the positive slope phase, the integration time is controlled by means of full-scale fine adjust values. The temperature dependent full-scale fine adjust values are produced from the preprogrammed values in memory by using interpolation techniques. For example, in the case of a piezo-resistive pressure sensor application, the temperature sensing is undertaken by intermittently sensing the temperature of the measuring circuitry using an on-chip temperature sensor, or the temperature at the top of the sensor bridge using the pressure sensors, or by using external temperature sensors. Pressure measurement depends on the plus and minus outputs of the sensor bridge, and measurement is performed by appropriately adjusting the integrator to provide for temperature compensation during the analog-to-digital conversion process.

Claims58

Dependent claims

An apparatus for measurement signal compensation comprising:

an analog-to-digital converter operating in a dual slope integration mode, the converter including an integrator having a first input port for selectively receiving either the analog measurement signal or a reference voltage, and a second input port for receiving a control voltage, the converter further including a comparator connected to an output of the integrator, and a counter for controlling the number of steps during the positive slope phase of integration;
a controller connected to the first input port of the integrator for providing the reference voltage to the integrator during a negative slope phase of integration;
and
an amplifier having a switchable gain, an output of the amplifier being connected to the first input port of the integrator, wherein the controller includes a microprocessor.

1 more element

Dependencies are inferred from the claim text.

Microprocessor controlled sensor signal conditioning circuit

Life of this patent

Microprocessor controlled sensor signal conditioning circuit

Life of this patent

Abstract

Claims58