Patents Assigned to Instrumention Northwest, Inc.
  • Patent number: 5460049
    Abstract: A strain gauge exhibits temperature offset errors and span errors which vary from device to device and vary as a function of temperature. A digitally-compensated strain-gauge apparatus executes embedded calibration and compensation programs for improving accuracy over a wide temperature range. Pressure measurement error bands are reduced to approximately to 0.03% of full scale for a 5 psi device over a 0.degree. C. to 50.degree. C. temperature range. A calibration program defines parameters for compensating for such errors. During field operation, a compensation program uses the calibration parameters to generate a more accurate pressure measurement. According to the compensation scheme, current normalized voltage and bridge impedance are derived from the raw data. A first-pass temperature estimate then is derived from the result. The derived first-pass temperature estimate is plugged into a temperature offset error function to find the temperature offset error at the estimated temperature.
    Type: Grant
    Filed: January 26, 1994
    Date of Patent: October 24, 1995
    Assignee: Instrumention Northwest, Inc.
    Inventor: Michael S. Kirsch