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On-site calibration device and method for nonlinearity correction for flow sensor/transmitter

  • US 5,479,812 A
  • Filed: 07/15/1994
  • Issued: 01/02/1996
  • Est. Priority Date: 07/15/1994
  • Status: Expired due to Term
First Claim
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1. The method for providing calibrated flow sensor units for connection to variable air volume measurement and control apparatus, comprising:

  • a. connecting a sensor unit to produce measurements of air flow or pressure as a differential voltage output signal,b. measuring three pressure values with the sensor unit and applying corrections to these measurements,c. entering a pickup relationship between flow and pressure drop for the sensor unit into storage,d. using the pickup relationship expressed as a series of point values, and the three pressure values, calculating points on a linearization curve as a series of point values,e. using the unit with gain and offset preset, measure the sensor unit'"'"'s signal output responsive to air flow at the unit'"'"'s intended installation site at at least three additional conditions;

    no flow, minimal flow, and full flow or maximum flow,f. adjusting these air flow responsive values by employing duct area values of a duct in which the sensor unit is deployed, and adjust the linearization curve to these adjusted air flow responsive values.

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