Torque Measurement Using Differential Amplification for Bias Compensation
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Solution Overview
Problem
Existing electronic torque wrenches suffer from inaccuracies due to unbalanced strain gauge assemblies producing a characteristic analog signal without applied torque, affecting resolution and accuracy of torque measurements.
Innovation Solution
An apparatus and method utilizing a strain gauge assembly with a differential voltage amplifier circuit calibrated to a bias voltage to reduce the characteristic voltage, combined with an analog-to-digital converter and processing circuitry to determine torque values accurately.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a strain gauge assembly is used to measure torque, then torque measurement capability is provided, but the unbalanced strain gauge produces a characteristic analog signal without applied torque that degrades measurement accuracy and resolution
Solution Approach 1:
The patent extracts and removes the harmful bias voltage signal from the strain gauge output through differential amplification. The differential voltage amplifier circuit is configured to reject the common-mode bias voltage while amplifying only the differential torque-related signal, effectively separating and eliminating the harmful component.
Solution Approach 2:
The patent introduces a differential voltage amplifier circuit as an intermediary between the strain gauge assembly and the signal processing stages. This intermediary component processes the strain gauge output by amplifying the torque signal while simultaneously rejecting the bias voltage, acting as a mediator that transforms the problematic signal into a usable measurement.
2Measurement precision
If the characteristic voltage from the strain gauge is not compensated, then the circuit design is simpler, but the torque measurement resolution and accuracy deteriorate at lower torque values
Solution Approach 1:
A differential voltage amplifier circuit is introduced as an intermediary component between the strain gauge assembly and the analog-to-digital converter. This amplifier selectively amplifies the torque-related differential signal while rejecting the common-mode bias voltage, thereby improving measurement resolution without requiring complex compensation circuits.
Solution Approach 2:
The patent changes the electrical parameters of the signal by using differential amplification with specific gain settings. The amplifier is configured to amplify the small differential torque signal while maintaining rejection of the larger common-mode bias voltage, effectively changing the signal-to-noise ratio in favor of the torque measurement.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances torque measurement accuracy by compensating for strain gauge bias, providing precise torque readings even at lower values.
Implementation Method 1
a strain gauge assembly configured to measure the applied torque, and produce an analog electrical signal that varies in voltage with the applied torque
Implementation Method 2
a differential voltage amplifier circuit configured to receive the analog electrical signal, and amplify the analog electrical signal to produce an amplified analog electrical signal
Data Source
AI summary
An apparatus such as an electronic torque wrench (100) is provided that includes a strain gauge assembly (202), differential voltage amplifier circuit (204), analog-to-digital converter (ADC) (206) and processing circuitry (208). The strain gauge assembly (202) measures an applied torque, and produces an analog electrical signal that varies in voltage with the applied torque; and the differential voltage amplifier circuit (204) amplifies the analog electrical signal to produce an amplified analog electrical signal. The strain gauge assembly (202) has a characteristic analog signal produced without any applied torque, and the differential voltage amplifier circuit (204) is biased to a bias voltage that is calibrated to reduce the characteristic voltage in the amplified analog electrical signal. The ADC (206) converts the amplified analog electrical signal to an equivalent digital electrical signal. And the processing circuitry (208) determines the torque value of the applied torque from the equivalent digital electrical signal, and outputs an indication of the torque value.