DDZ—Ⅲ型仪表技术讲座——第九讲 温度变送器(下)

第三节热电阻温度变送器热电阻温度变送器由放大单元和量程单元两部份组成。量程单元由线性化器(信号回路)、另点调整回路、热电阻引线电阻补偿回路、反馈回路及集成稳压电源几部份组成。其量程单元原理线路示于图(3—1)。     

温度检测元件保护套管选型合理性的探讨

针对温度检测元件保护套管广泛应用于石油化工装置的现状,介绍了温度检测元件保护套管设计选型考虑因素。阐述了温度检测元件保护套管固有频率(natural frequency)和唤醒频率(strouhal frequency)的计算方法以及两者之间的关系。通过实例计算描述了对温度检测元件保护套管选型合理性的验证方法。     

浅谈压力变送器选型中需注意的几个问题

压力变送器的量程、精度选择是变送器选型中的一个重要内容,微压与微差压变送器尤为特殊,本文论述了选型时需注意的几个问题,应做到的几个要点,以便能选型出精度最高、性能最佳的变送器。     

气化炉激冷室液位的测量与控制

气化炉激冷室液位的测量与控制关系到气化炉及气化装置的安全,对于稳定料浆气化过程,延长气化炉的使用寿命具有重要的意义。本文介绍了气化炉激冷室液位的测量与控制方法,论述了用双法兰差压变送器测量气化炉激冷室液位时,变送器的量程和迁移量的计算方法以及保护双法兰差压变送器所采取的措施。     

DDZ-Ⅲ与S系列温度变送器

一、概述自动化仪表中温度变送单元仪表就是用来测量温度的仪表。它可将测温元件的信号转换成统一的标准信号,用于指示、调节和控制。根据测温元件、输入方式和安装场所的不同又可分为热电偶温度、毫伏、温差变送器与热电阻温度、毫伏、温差变送器,以     

电容式新型传感元件及其应用

本文介绍了电容式新型传感元件的结构原理、工作特性,并详细介绍了此种新型传感元件在测量气体、液体及蒸汽流量时的安装方法。电容式变送器广泛应用在电力、石油化工等部门。     

化工行业中压力变送器的选型及应用

压力变送器的类型、材质、量程、防爆等级等的选择与环境条件、应用工况、安装条件、介质特性、经济性等息息相关,变送器的合理选型可更好地保证变送器的使用寿命并确保化工生产过程的测量控制稳定。     

防止保护管因共振而损坏的计算方法

在化工厂中,热电阻等测温元件几乎到处皆有,带保护套管的测温元件在测量时,是直接插在被测的流体中,因此,若保护管折断,轻则设备损坏影响生产,重则造成意外的事故.目前大多数设计和使用单位,在选择保护管时,对其强度往往只考虑其能承受的容许压力,忽略了流体的旋涡频率的影响.     

压力变送器在化工领域的选型与应用

压力变送器的选型包括变送器的类型、材质、量程、防爆性能等多个方面,合理的选型不仅可以确保变送器的使用寿命,更能保障化工生产过程中的各流程得以稳定开展。变送器的选型受到诸如环境条件、应用工况、安装条件、介质特性与经济效益等各方面的影响。简要分析了变送器的选型及其在化工领域的应用。     

新式温度变送器

老式温度变送器比较笨重,因此它总是与放置测温元件的保护套管分开安装。美国Wahl Instruments公司研制成功一种新式温度变送器。由于它采用小型封     

Insect antifeedant properties of anthranoids from the genusVismia

Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.     

Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM

Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively. There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized. High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing, and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually preserves suspension stability during freezing. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago, IL. Tied for first place in The John A. Gordon Best Paper Competition.     

Ethanol and (−)-α-Pinene: Attractant Kairomones for Bark and Ambrosia Beetles in the Southeastern US

In 2002–2004, we examined the flight responses of 49 species of native and exotic bark and ambrosia beetles (Coleoptera: Scolytidae and Platypodidae) to traps baited with ethanol and/or (−)-α-pinene in the southeastern US. Eight field trials were conducted in mature pine stands in Alabama, Florida, Georgia, North Carolina, and South Carolina. Funnel traps baited with ethanol lures (release rate, about 0.6 g/day at 25–28°C) were attractive to ten species of ambrosia beetles (Ambrosiodmus tachygraphus, Anisandrus sayi, Dryoxylon onoharaensum, Monarthrum mali, Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, Xylosandrus compactus, Xylosandrus crassiusculus, and Xylosandrus germanus) and two species of bark beetles (Cryptocarenus heveae and Hypothenemus sp.). Traps baited with (−)-α-pinene lures (release rate, 2–6 g/day at 25–28°C) were attractive to five bark beetle species (Dendroctonus terebrans, Hylastes porculus, Hylastes salebrosus, Hylastes tenuis, and Ips grandicollis) and one platypodid ambrosia beetle species (Myoplatypus flavicornis). Ethanol enhanced responses of some species (Xyleborus pubescens, H. porculus, H. salebrosus, H. tenuis, and Pityophthorus cariniceps) to traps baited with (−)-α-pinene in some locations. (−)-α-Pinene interrupted the response of some ambrosia beetle species to traps baited with ethanol, but only the response of D. onoharaensum was interrupted consistently at most locations. Of 23 species of ambrosia beetles captured in our field trials, nine were exotic and accounted for 70–97% of total catches of ambrosia beetles. Our results provide support for the continued use of separate traps baited with ethanol alone and ethanol with (−)-α-pinene to detect and monitor common bark and ambrosia beetles from the southeastern region of the US.     

Methyl 2,4,6-decatrienoates Attract Stink Bugs and Tachinid Parasitoids

Halyomorpha halys (Stål) (Pentatomidae), called the brown marmorated stink bug (BMSB), is a newly invasive species in the eastern USA that is rapidly spreading from the original point of establishment in Allentown, PA. In its native range, the BMSB is reportedly attracted to methyl (E,E,Z)-2,4,6-decatrienoate, the male-produced pheromone of another pentatomid common in eastern Asia, Plautia stali Scott. In North America, Thyanta spp. are the only pentatomids known to produce methyl 2,4,6-decatrienoate [the (E,Z,Z)-isomer] as part of their pheromones. Methyl 2,4,6-decatrienoates were field-tested in Maryland to monitor the spread of the BMSB and to explore the possibility that Thyanta spp. are an alternate host for parasitic tachinid flies that use stink bug pheromones as host-finding kairomones. Here we report the first captures of adult and nymph BMSBs in traps baited with methyl (E,E,Z)-2,4,6-decatrienoate in central Maryland and present data verifying that the tachinid, Euclytia flava (Townsend), exploits methyl (E,Z,Z)-2,4,6-decatrienoate as a kairomone. We also report the unexpected finding that various isomers of methyl 2,4,6-decatrienoate attract Acrosternum hilare (Say), although this bug apparently does not produce methyl decatrienoates. Other stink bugs and tachinids native to North America were also attracted to methyl 2,4,6-decatrienoates. These data indicate there are Heteroptera in North America in addition to Thyanta spp. that probably use methyl 2,4,6-decatrienoates as pheromones. The evidence that some pentatomids exploit the pheromones of other true bugs as kairomones to find food or to congregate as a passive defense against tachinid parasitism is discussed.     

2007～2008年世界塑料工业进展

收集了2007年7月～2008年6月世界塑料工业的相关资料,介绍了2007～2008年国外塑料工业的发展情况,提供了世界塑料产量、消费量及全球各类树脂的需求量及产能情况.按通用热塑性树脂(聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂)、工程塑料(尼龙、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚)、特种工程塑料(聚苯·硫醚、液晶聚合物、聚醚醚酮)、通用热固性树脂(酚醛、聚氨酯、不饱和聚酯树脂、环氧树脂)不同品种的顺序,对树脂的产量、消费量、供需状况及合成工艺、产品应用开发、树脂品种的延伸及应用的进一步扩展等技术作了详细介绍.     

2005～2006年国外塑料工业进展

收集了2005年7月～2006年6月国外塑料工业的相关资料,介绍了2005—2006年国外塑料工业的发展情况。提供了世界塑料产量、消费量及全球各类树脂生产量以及各国塑料制品的进出口情况。作为对比,介绍了中国塑料的生产情况。按通用热塑性树脂（聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂）、工程塑料（聚酰胺、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚）、通用热固性树脂（酚醛、聚氨酯、不饱和树脂、环氧树脂）、特种工程塑料（聚苯硫醚、液晶聚合物、聚醚醚酮）的品种顺序,对树脂的产量、消费量、供需状况及合成工艺、产品开发、树脂品种的延伸及应用的扩展作了详细的介绍。