用于远传测温的T／F转换接口

单片机用于测温,通常对A/D转换接口的转换速度要求不高,但要求有较高的精度和较低的价格。我们选用单片V/F转换器LM331和一块廉价的通用型四运放LM324,构成精度较高、价格低廉的远传测温T/F转换接口,其原理如图1所示。 (一)电路分析该接口电路由传感器驱动、电压放火和V/F转换等三部分组成。运放A_1、A_2(LM324N)以及晶体管T_1～T_4等组成一对恒流源,驱动三线制的热电阻R_t。这样可以消     

储罐两玻璃管液位计液面不等高的原因

玻璃管液位计是储罐和容器等设备普遍用以直观测量液位的指示器,其结构简单,价格低廉。我厂在使用该液压计测量储罐某些物料液位时,发现其上下段衔接处出现了液位不在同一水平面上的现象,见下图。由该图可见,管1和管2之间存在一液位差h。这一现象曾使一些同志百思不得其解,有人说这是毛细管现象,但又无法说清楚道理。     

大团囊虫草菌胞内多糖发酵优化和抗氧化活性研究(英文)

Cordyceps ophioglossoides is a valuable traditional medicinal material.We have found that intracellular polysaccharide(IPS) is the major biologically active ingredient in Cordyceps ophioglossoides.This study is the first time to optimize the yield of IPS from Cordyceps ophioglossoides.The optimal medium for IPS production consists of glucose 54.50 g·L·1,yeast powder 25.50 g·L·1,NaH2PO4 0.4 g·L·1 and K2HPO4 0.4 g·L·1.The suggested culture conditions are 24 ℃,initial pH 4.5 with a rotary speed of 120 r·min·1 for 168 h.The yield of IPS is 737.93 mg·L·1,which is 50% higher than the yield under the conditions prior to optimization.The anti-oxidative activities of IPS in Cordyceps ophioglossoides L2 are also characterized using various in vitro assay.The anti-oxidative activity may explain the reason why IPS from Cordyceps ophioglossoides can be used to fight against neurodegenerative dis-eases and menopausal symptoms.