Electric Field Measurement Circuit With Parasitic Capacitance Compensation
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Solution Overview
Problem
Existing electric field measuring devices face precision issues due to parasitic input capacitance in the amplifier, leading to attenuated voltage signal amplitudes and reduced measurement accuracy, especially when using semiconductor amplifiers with varying input capacitance values.
Innovation Solution
An electric field measuring device that includes an electric field detection unit, an amplifier with series resistance, a reference capacitive element, a step wave generating unit, and an information processing unit to calculate and apply an amplitude compensation factor, compensating for parasitic capacitance effects and improving measurement precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a semiconductor amplifier is used to read the voltage signal from the electric field antenna, then the device complexity is reduced and ease of manufacture is improved, but the input capacitance of the amplifier causes signal amplitude attenuation and measurement precision deteriorates
Solution Approach 1:
A capacitor coupling circuit is introduced as an intermediary component between the electric field antenna and the amplifier. This capacitor coupling circuit mediates the connection by blocking DC components while allowing AC signal components to pass, thereby preventing the amplifier's input capacitance from directly loading the antenna's output capacitance and causing amplitude attenuation.
Solution Approach 2:
The coupling path is segmented into distinct functional sections: the electric field antenna, the capacitor coupling circuit, and the amplifier. By segmenting the direct connection, the harmful capacitive interaction is isolated, and each component can operate within its optimal performance range without being adversely affected by the others.
2Measurement precision
If the amplifier input capacitance is reduced to improve measurement precision, then measurement precision is improved, but manufacturing costs increase due to stricter component specifications
Solution Approach 1:
The capacitor coupling circuit serves as a mediator that eliminates the need for amplifiers with extremely low input capacitance. By introducing this intermediate coupling stage, ordinary amplifiers with standard input capacitance values can be used while still achieving high measurement precision, thus avoiding the need for expensive, specially specified components.
3Measurement precision
If a reading circuit with high input impedance is used to read the voltage from the electric field antenna, then the signal amplitude attenuation is reduced and measurement precision is improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The capacitor coupling circuit acts as a simple yet effective intermediary that provides high input impedance to the antenna without requiring complex circuit topologies. This straightforward capacitive coupling approach achieves the desired high impedance effect while keeping the overall device complexity low and manufacturing straightforward.
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
The solution enhances the precision of electric field measurements by effectively compensating for signal attenuation caused by parasitic capacitance, maintaining measurement accuracy despite variations in amplifier input capacitance, and reducing manufacturing costs.
Implementation Method 1
An electric field antenna is typically composed of two electrode plates that are separated from and counter to each other. An electric field between the electrode plates is detected as a voltage that arises between the electrode plates.
Implementation Method 2
an amplifier that receives input of the voltage signal via a series resistance, and buffers or amplifies the voltage signal to output the voltage signal
Implementation Method 3
a reference capacitive element that has a reference capacitance, and has an output end connected between an output end of the series resistance and an input end of the amplifier
Data Source
AI summary
An electric field measuring device measures an electric field corresponding to an inter-electrode voltage between two electrodes, based on a voltage signal that arises at an electric field antenna including the two electrodes because of the electric field. The electric field measuring device includes an amplifier, a reference capacitive element, a GPIO that generates a step wave, and a microcomputer that processes a voltage signal. The microcomputer inputs the step wave to the amplifier, using the GPIO, obtains a step response waveform, and obtains an amplitude compensation factor, based on the step response waveform. The microcomputer compensates the voltage signal, using the amplitude compensation factor.