Conversion Configuration
Analog-to-digital conversion configuration where the reference voltage is derived from the same source that powers the sensor. Using a ratiometric adc reference eliminates errors caused by fluctuations in the excitation voltage. The digital output becomes a ratio of the input signal to the supply voltage rather than an absolute value.
This technique is common in bridge-based sensing systems.
Error Cancellation
If the supply voltage drifts by one percent, the sensor output and the reference voltage both change by the same proportion. Because the ratiometric adc reference tracks these changes, the resulting digital count remains stable. Regulators are unnecessary.
The system maintains its precision without the cost of high-stability external voltage sources.
Noise Rejection
Low-frequency noise on the power rail appears as common mode noise to the converter. Implementing a ratiometric adc reference ensures this noise is cancelled during the sampling phase.
Metrological Requirement
Proper implementation requires that the sensor and the converter share a common ground and a stable connection. The ratiometric adc reference must be filtered to remove high-frequency transients that might not be mirrored in the sensor output. Calibration verifies that the ratio remains constant across the full operating range of the power supply.
This ensures that the measurement integrity is maintained even when the battery or external supply voltage varies over time.
