| 摘要 |
<p>In photoelectric apparatus such as a pulse oximeter for monitoring a parameter of the blood in a living organism, a dark current correction signal is applied to the input at the preamplifier 34. The correction signal is substantially equal in magnitude but opposite in sense to the photodetector output during dark intervals when the illumination means of the apparatus is disabled. Because dark current correction is accomplished at the input 38 of the preamplifier 34, the preamplifier 34 has substantially increased resistance to overloading caused by ambient light and hence may have higher gain.</p> |
