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
通過發(fā)展?jié)穸缺O(jiān)測系統(tǒng)，提供一個監(jiān)測單元的網(wǎng)絡，集中監(jiān)控，來對那些建筑構件的可能造成損害的失敗提前預警，如持續(xù)的高濕度，這是眾所周知的導致木材和磚石腐敗和破壞的原因。系統(tǒng)設計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低維修安裝和長期客戶的滿意度來說是至關重要的。
本文描述了一種新型濕度傳感器的發(fā)展來滿足準確度的需求；沒有種類刻度是必要的。該傳感器由兩對平行電極組成，相當于有六個電阻的網(wǎng)絡，提供了測量濕度梯度的潛力。電極嵌入了一個圓柱形的、高耐久性的木材緩沖區(qū)。評估了當今的幾種測試技術，我們描述了一個用于連接數(shù)據(jù)采集系統(tǒng)的產(chǎn)品原型的性能，結果表明，為了建筑行業(yè)的有可能的利益，在所有情況下，有必要對木材的水分含量進行準確、長期的測量，如在購買、治療、建設和測量方面。
關鍵字：濕度傳感器、木材、儀器
1.簡介
木材中的水分和很多因素有關。如在裝置和終極含水量之間存在的實質(zhì)的變化，會引起翹面、收縮、扭曲變形[1]?？顾p性嚴重地受到木材水分含量的影響，就像細菌的移植強烈地受到水分含量的影響。例如，如果水分的含量在超過25%左右時，真菌的衰減就會急劇增加，特別是那些被歸類為“不耐用”的木材[2]。手持式水分測量儀經(jīng)常被用于監(jiān)測水分含量，但是由于單個的讀數(shù)只能在選定的點采取，測量就只能局限于地表或接近地表的地方。對于耐抗類型的儀器，如果木材種類和溫度校正，忽略顆粒定位和可能的濕度梯度，測量值將會存在很大的誤差。
對于大型和/或難以進入的地區(qū)來說，具有長期可靠性的濕度傳感器小