Abstract: The disclosure relates to a self-calibrated buffered-voltage DAC, comprising: a DAC (101) configured to receive an input digital signal (Din) and output a first analog voltage signal (V1); a buffer amplifier (102) configured to receive the first voltage signal (V1) from the DAC (101) and provide a buffered second analog voltage signal (V2); a voltage to frequency converter (201) configured to selectively receive the first and second voltage signals (V1, V2) and provide first and second output signals at respective first and second frequencies (fLx); a counter (202) configured to receive the output signals from the voltage to frequency converter (201) and provide respective first and second digital output signals (D1, D2) corresponding to the respective first and second frequencies (fLx); a comparator (203) configured to receive the first and second digital output signals (D1, D2) and provide a digital calibration offset (?Din); and a DAC error code module (311) configured to receive a digital input code (Din)

Abstract: A device for detecting soil nutrients on site, including an extracting grid, an on-site real-time detection assembly and a transfer assembly for transferring a soil extract from the extracting grid to the on-site real-time detection assembly. A soil nutrient detection method using the device and a microfluidic chip are also provided. The microfluidic chip includes a cover plate and a base plate. The base plate includes a soil extract feeding groove, a quantitative feeding groove, a reagent storage groove, and a serpentine groove.

Abstract: An auto-focusing optimization method for a camera and a camera are provided. The auto-focusing optimization method for a camera includes: shooting, in an focusing manner, at least the first image and the second image after the camera is started; synthesizing the first and the second image; and displaying an image after synthesis processing. The above scheme is capable of optimizing an image shot in a focusing manner and improving the definition of the image.

Abstract: An auto-focusing optimization method for a camera and a camera are provided. The auto-focusing optimization method for a camera includes: shooting, in an focusing manner, at least the first image and the second image after the camera is started; synthesizing the first and the second image; and displaying an image after synthesis processing. The above scheme is capable of optimizing an image shot in a focusing manner and improving the definition of the image.