US 6,924,649 B2 · Sensor read out

Abstract

A circuit and a method to measure continuously the resistance of variable resistors in series as e.g. potentiometers within a sensor, used for e.g. a joystick, has been achieved. The voltage across said sensor comprising any number of variable resistors is stabilized. A constant current source is providing a minimum current through said sensor. A variable current source is used to zoom variations of current through the sensor caused by variations of resistance of the sensor. Said variable current is mirrored and by measuring the voltage across a shunt resistor the total resistance of the sensor is identified. Using ports between each of the resistors, voltages can be measured representing the resistance of each of the variable resistors using known equations of voltage dividers. Any number of variable resistors can be used in the circuit invented.

Claims20

Dependent claims

A circuit to measure continuously the resistance of variable resistors in a sensor comprising:

a sensor comprising more than one variable resistor in series and one or more output ports providing signals identifying the variable resistance of each of said variable resistors;
a means of a constant current source providing a part of the current flowing through said sensor comprising variable resistors;
a means of a variable current source for the remaining part of the current flowing through said sensor to adapt variations of resistance of said sensor;
a means of stabilizing the voltage across said sensor;
a means to mirror said variable current;
a means of stabilizing the voltage across said current mirror;
and
a means to use said mirrored current to identify the total resistance of said sensor.

5 more elements

A method to measure continuously the resistance of variable resistors in a sensor comprising:

providing a sensor comprising more than one variable resistors in series and one or more output ports providing signals identifying the variable resistance of each of said variable resistors, a means of a constant current source providing a part of the current flowing through said sensor comprising variable resistors, a means of stabilizing the voltage across said sensor, a means of a variable current source for another part of the current flowing through said sensor to adapt variations of resistance of said sensor, a means to mirror said variable current, a means of stabilizing the voltage across said current mirror, and a means to use said mirrored current to identify the total resistance of said sensor;
stabilize the voltage across said sensor;
provide a constant part of the current flowing through the sensor;
provide a variable current source for the remaining part of the current flowing through the sensor to cover variations of resistance of said sensor;
mirror said variable current representing variations of the resistance of the sensor;
identify the total resistance of the sensor by measuring the voltage of said mirrored current across a known shunt resistor;
and
identify the resistance of each variable resistor within the sensor by representing voltages.

5 more elements

Dependencies are inferred from the claim text.

Sensor read out

Life of this patent

Sensor read out

Life of this patent

Abstract

Claims20