A/D conversion circuit and conversion method thereof

Abstract

The invention relates to an A / D converting circuit, comprising a high-precision reference voltage source, an analog switch with the function of more choosing one, a charging resistor and a V / F converter; the analog switch has n+2 paths of input pins, a control signal input end and an output pin; wherein, the two input pins are respectively connected with the ground and the high-precision reference voltage source; the rest n paths of input pins are used for receiving all voltage signal to be detected; the control signal input end is connected with a control signal output end of a digital processor; the output pins are connected with a voltage signal input end of the V / F converter by the charging resistor; a frequency signal output end of the V / F converter is connected with the signal input end of the digital processor; the invention also relates to an A / D conversion method which comprises the following steps of: gating all the input pins in sequence by controlling the analog switch with the function of more choosing one by the digital processor; calculating the frequency FGND, Fref and Fout of the input signals of all the input pins; and utilizing a formula that Vi is equal to Vref(Fout-FGND)(Fref-FGND) to calculate the voltage amplitude Vi of the input signal to be detected.

Description

technical field [0001] The invention relates to the technical field of visibility meters, in particular to an A / D conversion circuit in a visibility meter data collector and a conversion method thereof. Background technique [0002] At present, the A / D conversion circuit in the data collector of the visibility meter uses a V / F converter as the A / D converter, such as figure 1 As shown, it is composed of one end of the potentiometer R1 connected to the analog voltage signal input end of the V / F converter N1, and the other end of the potentiometer R1 is used to receive the voltage signal V input to the data collector. i , the digital signal frequency F output by the digital frequency output terminal of the V / F converter N1 out Send it to the data processor (CPU) N2 of the visibility meter for subsequent processing; the A / D conversion circuit adjusts F by changing the resistance value of the potentiometer R1 out with V i Each circuit needs to be calibrated separately, the ope...

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Problems solved by technology

[0006] f 0 is the output frequency when the input voltage is 0V, that is, the zero frequency, K v is the conversion ratio coefficient of the V / F converter, in actual use, F 0 、K v , the value of R1 will drift with the change of temperature and time, F 0 The change of K and R1 is the zero point drift, and the change of K and R1 is the gain drift. When a fixed F 0 , K, R1 value calculation V i error occurs when

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