Abstract
The moisture monitoring system being developed provides a network of monitoring cells, centrally monitored, to give early warning of potentially damaging failures of building components, generating high and persistent moisture levels, which are known to cause decay and damage to timber and masonry. The most critical aspect of system design is the useful range of the sensors, and their performance and reliability are crucial to a low maintenance installation and long-term customer satisfaction.
The paper describes the development of a new moisture sensor to meet the requirements with respect to accuracy; no species calibration is needed. The sensor consists of two pairs of parallel electrodes, equivalent to a network of six resistances, providing the potential for measuring moisture gradients. Electrodes are embedded with a cylindrical, high durability wood buffer. Several existing measurement techniques are eva luated. Performance of a prototype used in connection with a datalogging system is described. Results demonstrate the possible benefit to the construction industry in all situations where there is the need for an accurate long term measurement of the moisture content (MC) of timber, for example, in purchase, treatment, construction and surveying.
Key words: Moisture sensors, timber, instrumentation
1 Introduction
Moisture is associated with a range of problems in timber. For example, warping, shrinkage and distortion in service can occur where substantial variations exist between the installation and final moisture content (MC) [1].The resistance to decay is severely affected by the MC of timber as the colonisation of fungi is strongly dependent on the MC. For example, if the MC is above around 25% the probability of fungal decay increases dramatically, especially where the timber is classed as “nondurable” [2].Hand-held moisture meters are frequently employed for monitoring


摘要
通過(guò)發(fā)展?jié)穸缺O(jiān)測(cè)系統(tǒng)，提供一個(gè)監(jiān)測(cè)單元的網(wǎng)絡(luò)，集中監(jiān)控，來(lái)對(duì)那些建筑構(gòu)件的可能造成損害的失敗提前預(yù)警，如持續(xù)的高濕度，這是眾所周知的導(dǎo)致木材和磚石腐敗和破壞的原因。系統(tǒng)設(shè)計(jì)最重要的方面就是傳感器的有用范圍，它們的性能和可靠性對(duì)低維修安裝和長(zhǎng)期客戶(hù)的滿(mǎn)意度來(lái)說(shuō)是至關(guān)重要的。
本文描述了一種新型濕度傳感器的發(fā)展來(lái)滿(mǎn)足準(zhǔn)確度的需求；沒(méi)有種類(lèi)刻度是必要的。該傳感器由兩對(duì)平行電極組成，相當(dāng)于有六個(gè)電阻的網(wǎng)絡(luò)，提供了測(cè)量濕度梯度的潛力。電極嵌入了一個(gè)圓柱形的、高耐久性的木材緩沖區(qū)。評(píng)估了當(dāng)今的幾種測(cè)試技術(shù)，我們描述了一個(gè)用于連接數(shù)據(jù)采集系統(tǒng)的產(chǎn)品原型的性能，結(jié)果表明，為了建筑行業(yè)的有可能的利益，在所有情況下，有必要對(duì)木材的水分含量進(jìn)行準(zhǔn)確、長(zhǎng)期的測(cè)量，如在購(gòu)買(mǎi)、治療、建設(shè)和測(cè)量方面。
關(guān)鍵字：濕度傳感器、木材、儀器
1.簡(jiǎn)介
木材中的水分和很多因素有關(guān)。如在裝置和終極含水量之間存在的實(shí)質(zhì)的變化，會(huì)引起翹面、收縮、扭曲變形[1]?？顾p性嚴(yán)重地受到木材水分含量的影響，就像細(xì)菌的移植強(qiáng)烈地受到水分含量的影響。例如，如果水分的含量在超過(guò)25%左右時(shí)，真菌的衰減就會(huì)急劇增加，特別是那些被歸類(lèi)為“不耐用”的木材[2]。手持式水分測(cè)量?jī)x經(jīng)常被用于監(jiān)測(cè)水分含量，但是由于單個(gè)的讀數(shù)只能在選定的點(diǎn)采取，測(cè)量就只能局限于地表或接近地表的地方。對(duì)于耐抗類(lèi)型的儀器，如果木材種類(lèi)和溫度校正，忽略顆粒定位和可能的濕度梯度，測(cè)量值將會(huì)存在很大的誤差。
對(duì)于大型和/或難以進(jìn)入的地區(qū)來(lái)說(shuō)，具有長(zhǎng)期可靠性的濕度傳感器小