台达ADC电桥测量技术

　　介绍

　　压力，负载，温度，加速度传感器许多其他物理量往往采取的形式惠斯登电桥。这些传感器可以是非常线性的随着时间和温度的稳定。然而，最如果你不弯曲它们，自然界中的事物是线性的多。在一个负载细胞的情况下，虎克定律，材料中的应变与所施加的应力成正比—只要压力没有接近材料的屈服点（“不归点”的材料永久变形的）。其后果是负载基于电阻应变计的电池将有一个非常小电输出往往只有几毫伏。在尽管如此，仪器有100000个分辨率更多的可能。本申请说明高分辨率测量的一些新方法成为可能的线性技术的家庭20 -和24位Δ∑模数转换器。

　　通常在实施20或24位的最大障碍电桥测量电路正在超越常规信号调理电路所需的12 -16位ADC。只需在电路中替换24位ADC专为12位ADC不保证一个4096倍分辨率增加。虽然性能可以提高，24位ADC可能只是揭示了局限性的模拟前端，并充分受益的24位ADC将无法实现。

　　In a typical 12-bit measurement system， the signal conditioning amplifier requires a very high gain in order to make use of the full ADC input range. A sensor with a 10mV fullscale output requires a gain of 500 to use the full input range of a typical 5V input ADC. A filter may be required to reduce noise at the expense of settling time. Additional difficulties arise when dealing with the large common mode voltage typical of a bridge sensor. Most instrumentation amplifiers have a large discrepancy between the typical CMRR and guaranteed minimum， which may require an additional trim.

　　Linear Technology’s differential input delta sigma ADCs address these concerns and make it possible to extract maximum resolution from a variety of bridge measurement devices. The outstanding resolution of these ADCs eliminates the need for amplification in many applications. Even in extreme cases where amplification is required， high resolution ADCs such as the LTC® 2440 allow very modest amplifier gains. A fully differential amplifier topology eliminates the differential-to-single-ended stage of a typical 3-amplifier instrumentation amplifier along with the CMRR limitations of this stage.