60 VMM2404Application Examples10.7.2. Variable ResistanceVariable resistance sensors change impedance to represent it's measured value,and are compatible with analog inputs.Variable resistance sensors are typically used in thermal and pressureapplications. They work by changing the voltage reading on the sensor accordingto changes in pressure or temperature in the application.The VMM2404 cannot measure resistance directly.To make the VMM2404 measure resistance accurately, do the following: Include a precision pull-up resistor between the sensor and the sensor poweroutput (called SENSOR_SUPPLY). Ensure the value of the precision resistor allows the maximum possibleresolution for the sensor's input. Dimension the precision resistor to get the maximum voltage range from thesensor.Note: Variable resistance sensor accuracy may suffer at the extremes of thesensor's range. A tolerance analysis should be performed to ensuremeasurement accuracy is acceptable for your application.The following shows a typical variable resistance sensor connection:Internal to productAnalog InputSensor PowerVariableResistanceSensorPrecisionResistorFigure 28: Variable resistance sensor connection
