Method and apparatus for the calibration and compensation of sensors

Abstract

A transducer system that can be used to measure various parameters includes a programmable circuit that may be mounted in the same package as a sensor. Such a system may include pressure sensors that are optimized to measure very low pressures. The programmable circuit may be an application specific integrated circuit (ASIC) that is configured to modify the output of the sensor to correct for possible errors in the sensor. A method of using a programmable circuit to calibrate a sensor may include coupling the programmable circuit to a computer and to a testing station. The computer can be configured to vary the conditions of the testing station and determine the response of the sensor. Then the programmable circuit can be programmed to produce a desired response.

1 . A transducer comprising: 
 a sensor configured to sense a parameter and to produce an output signal based thereon; and    a programmable circuit having an input port configured to receive the output signal of said sensor, wherein said programmable circuit is configured to produce an output signal based on said output signal of said sensor.    
     
     
         2 . The transducer of  claim 1 , wherein said sensor comprises a pressure sensor.  
     
     
         3 . The transducer of  claim 2 , further wherein said programmable circuit is configured to produce a linear output signal based on said output signal of said sensor.  
     
     
         4 . The transducer of  claim 2 , said pressure sensor being optimized to operate in low pressure environments.  
     
     
         5 . The transducer of  claim 2 , wherein said pressure sensor comprises a pair of pressure sensors in a wheatstone bridge configuration.  
     
     
         6 . The transducer of  claim 1  wherein said programmable circuit and said sensor are located within a case.  
     
     
         7 . The transducer of  claim 1 , said programmable circuit comprising an application specific integrated circuit (“ASIC”).  
     
     
         8 . The transducer of  claim 1 , said sensor comprising a pair of sensors, said pair of sensors being mechanically and electrically cross-coupled with each other such that errors associated with one of said pair of sensors is compensated or substantially cancelled by errors associated with the other of said pair of sensors.  
     
     
         9 . The transducer of  claim 1  wherein said programmable circuit is configured to produce a linear output signal based upon said output of said sensor.  
     
     
         10 . The transducer of  claim 1  wherein said programmable circuit is configured to produce an output signal that corrects for thermal effects on said sensor.  
     
     
         11 . The transducer of  claim 1  wherein said programmable circuit is configured to produce an output signal that is within a predetermined range of output levels.  
     
     
         12 . The transducer of  claim 11  wherein said predetermined range is from about 0.25 volts to about 4.25 volts.  
     
     
         13 . A method of calibrating a transducer comprising a sensor coupled to an ASIC, said method comprising: 
 testing the sensor at a first predetermined condition to determine the output of the CB=0 at decision diamond  216 . If the there have been N consecutive CB=0,    programming the ASIC such that the output of the ASIC at the first predetermined condition is within a first predetermined range.    
     
     
         14 . The method of  claim 13  wherein said first predetermined condition comprises room temperature and zero pressure.  
     
     
         15 . The method of  claim 13  wherein the first predetermined range is the range approximately within 0.25% of 0.25 volts.  
     
     
         16 . The method of  claim 13  further comprising: 
 testing the sensor at a second predetermined condition to determine the output of the sensor; and  
 programming the ASIC such that the output of the ASIC at the second predetermined condition is within a second predetermined range.  
 
     
     
         17 . The method of  claim 16  wherein said second predetermined condition comprises room temperature and a maximum pressure.  
     
     
         18 . The method of  claim 16  wherein said second predetermined range is the range approximately within 0.25% of 4.25 volts.  
     
     
         19 . The method of  16  further comprising: 
 testing the sensor at a third predetermined condition to determine the output of the sensor; and  
 programming the ASIC such that the output of the ASIC at the third predetermined condition is within a third predetermined range.  
 
     
     
         20 . The method of  claim 19  wherein said third predetermined condition comprises a low temperature and zero pressure.  
     
     
         21 . The method of  19  further comprising: 
 testing the sensor at a fourth predetermined condition to determine the output of the sensor; and  
 programming the ASIC such that the output of the ASIC at the fourth predetermined condition is within a predetermined range.  
 
     
     
         22 . The method of  claim 21  wherein said fourth predetermined condition comprises a low temperature and maximum pressure.  
     
     
         23 . The method of  21  further comprising: 
 testing the sensor at a fifth predetermined condition to determine the output of the sensor; and  
 programming the ASIC such that the output of the ASIC at the fifth predetermined condition is within a fifth predetermined range.  
 
     
     
         24 . The method of  claim 23  wherein said fifth predetermined condition comprises a high temperature and zero pressure.  
     
     
         25 . The method of  claim 23  further comprising: 
 i) testing the sensor at a sixth predetermined condition to determine the output of the sensor; and  
 j) programming the ASIC such that the output of the ASIC at the sixth predetermined condition is within a sixth predetermined range.  
 
     
     
         26 . The method of  claim 25  wherein said sixth predetermined condition comprises a high temperature and maximum pressure.