Analog Amplifier Timeout Gating for Switching Jump Errors
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Solution Overview
Problem
Analog amplifiers in signal-processing units for force-measuring devices, such as gravimetric measuring devices, suffer from transfer errors due to their physically limited capabilities in following abrupt signal discontinuities, leading to variable scatter between units and temperature effects, which complicates manufacturing and increases costs.
Innovation Solution
A method involving a modulator and/or multiplexer with a switchover controller, where a processing stage is separated or blocked from the analog amplifier during a predetermined timeout phase, triggered by switching jumps, to correct transfer errors by matching the timeout duration to the amplifier's rise time or time constant, thereby eliminating scatter and temperature effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a DC power supply and DC amplification are used in the measuring device, then the circuit design is simple and cost-effective, but DC voltage errors such as thermo-voltage errors and voltage-offset errors occur along with excessive low-frequency noise
Solution Approach 1:
The patent applies periodic AC modulation to the DC power supply, converting the steady DC signal into a time-varying AC signal at a specific modulation frequency. This periodic action allows the measurement signal to be distinguished from DC offset errors and low-frequency noise through frequency separation, while the modulated signal can still be accurately demodulated back to DC values for measurement purposes.
Solution Approach 2:
The patent changes the operating parameter of the power supply from DC (zero frequency) to AC (modulation frequency), transforming the measurement system from a DC-coupled to an AC-coupled configuration. This parameter change shifts the measurement signal to a frequency range where thermal voltages and offset errors have minimal impact, thereby improving measurement precision while maintaining circuit simplicity.
2Measurement precision
If additional AC-modulation and -amplification techniques are applied to reduce measurement errors, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent designs the modulator and demodulator circuits to serve multiple functions: they not only perform the primary function of frequency conversion for noise rejection but also provide signal amplification, synchronization, and error correction capabilities. This multi-functionality reduces the need for separate dedicated circuits for each function, thereby limiting the increase in overall device complexity.
Solution Approach 2:
The patent introduces a modulator as an intermediary component between the DC power supply and the measurement circuitry. This intermediary converts the DC signal to AC for processing, and a demodulator acts as a second intermediary that converts it back to DC for measurement. These intermediary components enable precise measurement while keeping the overall architecture modular and manageable.
3Measurement precision
If high-precision amplifiers are used to eliminate transfer errors and temperature effects, then measurement accuracy is maintained, but manufacturing costs increase
Solution Approach 1:
The patent employs standard, cost-effective amplifiers rather than expensive high-precision amplifiers, accepting that these cheaper components have higher inherent noise and offset characteristics. By modulating the signal to a frequency range where these imperfections have minimal impact, the system achieves high measurement accuracy using inexpensive, readily available components, thereby reducing manufacturing costs.
Solution Approach 2:
The patent converts the harmful effect of amplifier imperfections (noise, offset, drift) into a manageable issue by frequency modulation. The modulation technique shifts the measurement signal away from the frequency range where amplifier defects are most problematic, effectively turning the limitation of cheap amplifiers into a non-issue through clever signal processing.
Data Source
AI summary
A method is disclosed for correcting transfer errors of an analog amplifier that occur following a jump in the amplifier input signal caused by switching. A measuring device includes at least one sensor as well as a signal-processing unit connected to the sensor and analog amplifier. The signal-processing unit includes at least one modulator and/or a multiplexer, an analog amplifier and at least one processing stage following the analog amplifier in the circuit chain. The processing stage, dependent on the point in time when the switching jump occurs, is separated from the latter during a predetermined timeout phase duration by means of a switch that is arranged between the analog amplifier and the processing stage and is controlled by a timeout controller, and/or dependent on the point in time when the switching jump occurs, said processing stage is blocked by a timeout controller during a predetermined timeout phase duration.