電流信號(hào)被廣泛應(yīng)用于儀表信號(hào)的輸出。為了給智能儀表提供廉價(jià)標(biāo)準(zhǔn)電流信號(hào)輸出
接口，可以使用RC低通濾波器，從PWM中分離出與占空比成正比的線性直流電壓信號(hào)。此電壓信號(hào)經(jīng)過由放大器組成的壓/流轉(zhuǎn)換產(chǎn)生穩(wěn)定的標(biāo)準(zhǔn)電流信號(hào)。同時(shí)，為了方便量程校準(zhǔn)，儀表采用軟件和硬件相結(jié)合的方法，對表征輸出電流信號(hào)大小的電壓進(jìn)行數(shù)模轉(zhuǎn)換，用軟件的方法確定量程的上下限。從而使整個(gè)標(biāo)準(zhǔn)電流輸出電路對所用元件的參數(shù)不敏感且結(jié)構(gòu)簡單、校準(zhǔn)方便、也降低了成本。
關(guān)鍵字：自動(dòng)化儀表；標(biāo)準(zhǔn)電流信號(hào)源；脈寬調(diào)制；自動(dòng)校準(zhǔn)

Abstract：The current signal is widely used for the instrument’s output signal. To provide
intelligent instruments with the cheap interface of the standard current sign, the RC low pass filter is used for producing a voltage signal which is proportion to PWM`s duty rate from PWM. This voltage signal generates the standard current signal via V/I convert. And, to make the instrument’s calibration convenient, the software is combined with the hardware. The ADC of the instrument sample the voltage signal which is represents the current signal. And the software calculates upper and lower limits of measure range. By this means, the system with the low price and the simple structure isn’t sensitivity to the component’s parameter, and measure range can be adjusted conveniently.
Keywords: automatization instrument, standard current signal source, PWM, spectral analysis; automatization calibrate