電流傳感器的基本知識

　　電流傳感器既可以是開路的也可以是閉環的。開環電流傳感器測量交流和直流電流，并在被測電路和傳感器的輸出之間提供電氣隔離（原電流測量而不與初級電路電接觸，提供直流隔離）。開環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，在電池供電的電路中通常是首選的。

　　閉環傳感器測量交流和直流電流，并提供電氣隔離。它們具有響應快、線性度高、低溫漂移等優點。閉環傳感器的電流輸出相對不受電噪聲的影響。閉環傳感器有時被稱為“零磁通”傳感器，因為它的霍爾效應傳感器反饋相反的電流進入次級線圈，卷繞在磁芯上，以使磁芯產生的磁通由初級電流產生零。閉環傳感器往往是傳感器的選擇時，高精度是必不可少的。

　　現在讓我們仔細看看這兩種類型，從開環傳感器開始。

　　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.