Bridge Sensor Readout Using Threshold Timing and Polarity Reversal
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Solution Overview
Problem
Existing methods for digitizing the differential output of sensor circuits or bridge circuits with two excitation nodes and two readout nodes are limited in accuracy and efficiency, lacking effective error detection capabilities.
Innovation Solution
A method and circuit for providing a digital value indicative of a physical quantity measured by a sensor or bridge circuit, involving the application of a time-varying biasing signal to the excitation nodes, generating time-varying output signals, and determining a digital value based on specific time, count, or index values related to threshold crossings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a classical ADC is used to digitize the differential output, then conversion is achieved, but measurement precision and error detection capabilities are insufficient
Solution Approach 1:
The patent segments the digitization process into multiple measurement cycles with different excitation polarities. Instead of a single ADC conversion, the system performs sequential measurements with reversed excitation signals, allowing differential calculation that eliminates common-mode errors and enables precision error detection through consistency checking of the differential results.
Solution Approach 2:
The patent changes the excitation parameters by reversing the polarity of the biasing voltage between measurement cycles. This parameter change allows the system to measure the same physical quantity under inverted conditions, and by comparing results, it can detect errors and improve measurement precision through differential calculation that cancels out systematic errors.
2Measurement precision
If a time-varying biasing signal is applied to enhance measurement capabilities, then error detection and precision are improved, but device complexity increases
Solution Approach 1:
The patent implements periodic action by applying biasing signals that alternate in polarity between measurement cycles. This periodic reversal of excitation signals is generated by a simple control circuit that switches the biasing voltage direction, enabling error detection and precision measurement without requiring complex additional hardware, as the periodic pattern itself carries the error-detection information.
3Reliability
If multiple measurement cycles with polarity reversal are implemented, then error detection capability is enhanced, but measurement time increases
Solution Approach 1:
The patent maintains continuity of useful action by performing measurements in back-to-back cycles without idle periods. The excitation polarity is reversed continuously between cycles, and the measurement process itself generates the error-detection data. This continuous operation ensures that error detection capability is achieved without significant time penalty, as the second cycle serves dual purposes: measuring the physical quantity and validating the first measurement for errors.
Data Source
AI summary
A method of providing a digital value indicative of a physical quantity to be measured by a sensor circuit or a bridge circuit that has two excitation nodes and at least one output node, comprises the steps of: a) applying a time-varying biasing signal to the excitation nodes, causing at least one output-node to provide a time-varying output signal; b) determining a first time value or a first count value or a first index related to a first event at which the first output signal passes a first threshold signal; c) providing a digital value indicative of the physical quantity to be measured based on said at least one time value or count value or index value.