Isolating Micro-Machined Die Packaging Stress during Automated Thermal Calibration
Automated thermal calibration must isolate packaging thermo-mechanical stress shifts from intrinsic silicon sensor signals using real-time compensation.
Zero-Point Voltage Shift
Offset Error
Baseline output variations in a transducer occur when the physical quantity is at its reference value. This zero-point voltage shift represents the null deviation after the device is powered and stabilized. It is the primary contributor to measurement uncertainty in low-level signal applications.
Mechanical Origin
Mechanical stress from the assembly process or thermal expansion mismatches typically cause the bridge to become unbalanced. Even without an external load, the internal resistors experience a strain that the circuit interprets as a small input. The zero-point voltage shift often changes over time as the packaging materials age and internal stresses redistribute.
Changes Environmental
Changes in the ambient environment cause the offset to move in a predictable but undesirable manner. The coefficient describing this movement is measured in microvolts per degree Celsius. Compensation circuits use an internal temperature sensor to apply a correction that cancels out the zero-point voltage shift before the data reaches the user.
Trimming Limit
Trimming procedures during the final manufacturing step reduce the initial offset to a manageable level. The remaining zero-point voltage shift must fall within the range that the downstream electronics can resolve. Periodic re-zeroing of the system allows for the removal of long term drift and ensures the sensor maintains its specified accuracy.