Wheatstone Bridge Voltage Offset Correction Circuit
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Solution Overview
Problem
Wheatstone bridge sensors face challenges with low full-scale output voltage and significant voltage offset due to resistor mismatching and temperature variations, requiring high-precision preamplification and offset correction, while also needing to minimize noise levels, especially 1/f noise, in low-speed physical measurements.
Innovation Solution
A device with a correction circuit that uses a current source and follower amplifier to replicate the supply voltage, generating a second current for a digital/analog converter to adjust and cancel out voltage offset, which is independent of amplifier gain and sensitive to resistor value changes, thereby correcting voltage offset automatically without high-cost sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-precision preamplification is used to amplify the low full-scale output voltage, then measurement precision is improved, but noise level increases due to amplifier 1/f noise
Solution Approach 1:
The patent applies preliminary action by performing offset correction before the signal enters the preamplifier. The correction circuit generates a compensation current that cancels the offset at the Wheatstone bridge output stage, ensuring that the preamplifier only amplifies the actual measurement signal without amplifying the offset. This preliminary correction prevents noise introduction while maintaining measurement precision.
2Measurement precision
If offset correction is performed after preamplification, then measurement precision is improved, but noise level increases because the offset is amplified along with the signal
Solution Approach 1:
The patent implements preliminary action by correcting the offset before preamplification occurs. The correction circuit is positioned at the input stage, generating a compensation current that eliminates offset at the source. This ensures subsequent amplification only affects the genuine measurement signal, not the offset, thereby preventing noise amplification while achieving high measurement precision.
3Device complexity
If a fixed offset correction value is used, then device complexity is reduced, but measurement precision deteriorates due to inability to follow supply voltage and resistor variations
Solution Approach 1:
The patent applies feedback by continuously monitoring the supply voltage through a follower amplifier and using this information to dynamically adjust the offset correction current. The correction circuit receives feedback about supply voltage changes and resistor value variations (through temperature effects), automatically adjusting the compensation current to maintain accurate offset cancellation across varying conditions without increasing overall device complexity.
4Measurement precision
If high-cost high-level sensors are used to achieve accurate measurements, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts and corrects the offset error component separately from the main measurement signal. By isolating the offset correction function in a dedicated correction circuit that operates independently from the main sensor element and preamplifier, the system achieves high measurement precision using standard, low-cost sensor components rather than requiring expensive high-level sensors. The offset correction is extracted as a separate compensating signal.
Data Source
AI summary
A circuit includes a Wheatstone bridge and a correction circuit operable to correct an output voltage offset of the Wheatstone bridge. The correction circuit includes a supply module configured to supply the Wheatstone bridge with a voltage and output a first current applied to the Wheatstone bridge and output a second current proportional to the first current. A digital/analog current converter outputs a correction current to the outputs of the Wheatstone bridge circuit in response to a digital correction signal and the second current.