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Help everyone, a general sensor signal to 0~3V voltage signal front circuit!

Hardware design
November 04, 2020 by Theron 502

I want to design a signal acquisition circuit to transmit the sensor signal to the AD sampling module. The sensor output signal amplitude used in the field is all 5V, but the superimposed bias voltage is different, such as 3~13V superimposed on 8V, or -3~-13V superimposed on -8V. Therefore, I want to design a general-purpose circuit. First use a high-pass filter circuit to filter out the DC part of the signal, and then superimpose the 5V boost level, the signal is converted to 0~10V, and finally the voltage divider circuit is converted to 0~3V. , In addition, does each level circuit have to add voltage to follow? Please advise from all the great gods, thank you very much! !

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Gabriele Posted on November 4, 2020

Is the output signal of your sensor a DC signal or an AC signal? (Although your amplitude is 5V), if it is a DC signal, your circuit will pass a C4 as soon as it comes in, and the ADC basically collects 0V!


Therefore, a reverse signal input can achieve signal amplitude attenuation, DC level shift, filtering, and impedance transformation output functions!

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  • Theron

    Theron Posted on November 4, 2020

    Hello, can you explain why the ADC will pick 0V after connecting a DC blocking capacitor? Doesn't the DC blocking capacitor only filter out AC signals below the cutoff frequency? Thank you

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Gabriele Posted on November 4, 2020

Therefore, I am asking about the characteristics of the sensor signal you mentioned "transmitting the sensor signal to the AD sampling module".


Usually raw sensor data such as temperature, humidity, pressure, and brightness are discrete voltage signals.

For example, a temperature sensor circuit built with a thermistor, thermistor and precision resistor divide the output voltage, use ADC to collect this voltage, calculate the resistance of the thermistor, and then query the thermistor characteristics to determine the temperature. In this case, if the temperature does not change or the change is small for a certain period of time, how does your isolated DC capacitor work?


But some sensors, such as electret MIC, collect environmental noise, because we usually define the cause as 20Hz~20KHz (human ear perception frequency), then your DC blocking capacitor is meaningful, and a suitable value can be used Filter out the effect of interference. Of course, the frequency response parameters are also introduced.

The audio ADC usually has a relatively high sampling rate. This is the recording!

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Danni Posted on November 4, 2020

Why not directly use low voltage op amp IC?

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