The invention relates to a true
root mean square value detection-based
soil moisture sensor, which comprises a power supply filter circuit, an active
crystal oscillator, a Schmidt trigger, a
signal attenuator, a probe and a true
root mean square value
detector. The Schmidt trigger shapes a high-frequency
sine wave or
square wave signal output by the active
crystal oscillator into a standard waveform
square wave signal, the amplitude of the standard waveform
square wave signal is reduced by the signal attenuator, a
resistor-
capacitor (RC) circuit consisting of the signal attenuator and the probe is charged and discharged periodically, a periodic charging and discharging curve waveform is obtained on the probe, and the true
root mean square value
detector converts a waveform
signal on the probe into equivalent
direct current voltage serving as a sensor output signal. When soil
moisture is different, the
equivalent capacitance of the probe is different, the charging and discharging waveforms are different, and the final output signals are different, so that the soil
moisture is measured according to the principle. The
soil moisture sensor has the characteristics of simple structure, small volume, low
power consumption, low cost, high soil adaptability, simple input / output interface and the like, is easy to apply and facilitates the development of secondary instruments.