Measuring and testing – Instrument proving or calibrating – Volume of flow – speed of flow – volume rate of flow – or mass...
Patent
1992-03-23
1994-03-22
Williams, Hezron E.
Measuring and testing
Instrument proving or calibrating
Volume of flow, speed of flow, volume rate of flow, or mass...
G01P 2100
Patent
active
052953874
ABSTRACT:
A micromachined accelerometer unit and a hybrid accelerometer circuit for processing a signal from the unit are mounted in the same package with the substrate of the hybrid circuit in a plane normal to the sensitivity axis of the accelerometer. For calibration, thick film resistors on the substrate are laser trimmed at two different temperatures in two stations. The package is mounted on a shaker table with the substrate normal to the direction of vibration and a trimming laser beam normal to the substrate is directed onto the substrate to trim the resistors while the package is being vibrated. The ac signal produced by the circuit is monitored by test equipment and compared to a reference value to determine any signal error and to control the laser beam. The laser beam has a finite range where the depth of focus is suitable for resistor trimming and the amplitude of vibration is much smaller than that range to permit trimming during the mechanical excitation. Alternatively, the amplitude of vibration is larger than the depth of focus and the operation of the laser is synchronized with the motion of the substrate to turn on the laser only when the resistor being trimmed is within the range of the depth of focus.
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N. H. Clark, "An Improved Method for Calibrating Reference Standard Accelerometers", Apr. 1983, pp. 103-107.
Buie Jack V.
Yost Gerald R.
Ashraf Nashmiya
Delco Electronics Corp.
Navarre Mark A.
Williams Hezron E.
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