Temperature measurement method using temperature coefficient timing for resistive or capacitive sensors
AssigneeLockheed Martin Energy Research Corporation
InventorsCharles L. Britton, Jr., M. Nance Ericson
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Abstract
A method and apparatus for temperature measurement especially suited for low cost, low power, moderate accuracy implementation. It uses a sensor whose resistance varies in a known manner, either linearly or nonlinearly, with temperature, and produces a digital output which is proportional to the temperature of the sensor. The method is based on performing a zero-crossing time measurement of a step input signal that is double differentiated using two differentiators functioning as respective first and second time constants; one temperature stable, and the other varying with the sensor temperature.
Claims14
A method for measuring the temperature of a temperature dependent sensor comprising the steps of:
- generating a step signal;
- differentiating said step signal with a first time constant means to produce a differentiated pulse, said first time constant means being independent of temperature;
- differentiating said differentiated pulse with a second time constant means to produce a doubly-differentiated pulse having a zero crossing, said second time constant means including said temperature dependent sensor;
- detecting said zero crossing with a comparator means;
- starting a digital counting means at the instant said step signal is generated;
- and
- stopping said digital counting means at the instant said zero crossing occurs;
- whereby the digital, output of said digital counting means has a known proportionality to the time said digital counting means is started to the time said digital counting means is stopped.
A method for measuring the temperature of a temperature dependent sensor comprising the steps of:
- generating a step signal;
- differentiating said step signal with a first time constant means to produce a differentiated pulse, said first time constant means being dependent on temperature and including said temperature dependent sensor;
- differentiating said differentiated pulse with a second time constant means to produce a doubly-differentiated pulse having a zero crossing, said second time constant means being independent of temperature;
- detecting said zero crossing with a comparator means;
- starting a digital counting means at the instant said step signal is generated;
- and
- stopping said digital counting means at the instant said zero crossing occurs;
- whereby the digital output of said digital counting means has a known proportionality to the time said digital counting means is started to the time said digital counting means is stopped.
An apparatus for measuring the temperature of a temperature dependent sensor comprising:
- a means for generating a step input;
- a first time constant means independent of temperature for differentiating said step input to produce a differentiated pulse;
- a second time constant means dependent on temperature for differentiating said differentiated pulse to produce a doubly-differentiated pulse having a zero crossing, said second time constant means including said temperature dependent sensor;
- a comparator means for detecting said zero crossing and providing a stop signal thereupon;
- an n-bit counter which begins counting at the instant said step input is generated, and stops counting at the instant said stop signal is received from said comparator means;
- a timebase for providing a fixed clock to said n-bit counter;
- and wherein the digital output of said n-bit counter is a function of the temperature of said temperature dependent sensor.
An apparatus for measuring the temperature of a temperature dependent sensor comprising:
- a means for generating a step input;
- a first time constant means dependent on temperature for differentiating said step input to produce a differentiated pulse, said first time constant means including said temperature dependent sensor;
- a second time constant means independent of temperature for differentiating said differentiated pulse to produce a doubly-differentiated pulse having a zero crossing;
- a comparator means for detecting said zero crossing and providing a stop signal thereupon;
- an n-bit counter which begins counting at the instant said step input is generated, and stops counting at the instant said stop signal is received from said comparator means;
- a timebase for providing a fixed clock to said n-bit counter;
- and wherein the digital output of said n-bit counter is a function of the temperature of said temperature dependent sensor.
Dependencies are inferred from the claim text.