電流傳感器的基本知識(shí)

　　電流傳感器的基本知識(shí)

　　電流傳感器既可以是開(kāi)路的也可以是閉環(huán)的。開(kāi)環(huán)電流傳感器測(cè)量交流和直流電流，并在被測(cè)電路和傳感器的輸出之間提供電氣隔離（原電流測(cè)量而不與初級(jí)電路電接觸，提供直流隔離）。開(kāi)環(huán)電流傳感器由于其低的工作功率要求和占用空間小的特點(diǎn)，在電池供電的電路中通常是首選的。

　　閉環(huán)傳感器測(cè)量交流和直流電流，并提供電氣隔離。它們具有響應(yīng)快、線(xiàn)性度高、低溫漂移等優(yōu)點(diǎn)。閉環(huán)傳感器的電流輸出相對(duì)不受電噪聲的影響。閉環(huán)傳感器有時(shí)被稱(chēng)為“零磁通”傳感器，因?yàn)樗幕魻栃?yīng)傳感器反饋相反的電流進(jìn)入次級(jí)線(xiàn)圈，卷繞在磁芯上，以使磁芯產(chǎn)生的磁通由初級(jí)電流產(chǎn)生零。閉環(huán)傳感器往往是傳感器的選擇時(shí)，高精度是必不可少的。

　　現(xiàn)在讓我們仔細(xì)看看這兩種類(lèi)型，從開(kāi)環(huán)傳感器開(kāi)始。

　　Open loop current sensors consist of a Hall sensor mounted in the air gap of a magnetic core （Fig. 1）。 A conductor produces a magnetic field comparable to the current. The magnetic field is concentrated by the core and measured by the Hall sensor. The signal from the Hall generator is low， so it is amplified， and it is this amplified signal that becomes the sensor’s output. Open-loop sensors normally have circuitry that provides temperature compensation and calibrated high-level voltage output. While they have a definite price advantage over closed-loop counterparts， their downside is that they can be prone to saturation and temperature drift. The drift can be minimized to some extent， however， by injecting a positive coefficient in the control current to reduce the drift in sensitivity over temperature.