HPV 莖流量傳感器/Sap Flow Sensor
HPV莖流量傳感器是一款校準型、低成本的熱脈沖液流傳感器，輸出校準液流量、熱速、莖水含量、莖溫等數(shù)據(jù)，功耗低，內置加熱控制，同時改善了傳統(tǒng)的加熱方式，其原理采用雙方法（DMA）熱脈沖法，測量范圍：-200~+1000cm/hr(熱流速度)或-100~+2000cm3/cm2/hr (莖流通量密度)，可廣泛用于于莖流量監(jiān)測、植物莖流蒸發(fā)計算、植物莖流蒸騰量、植物灌溉等
植物莖流是樹木內部的“水”運動，而蒸騰是從葉片通過光合作用蒸發(fā)流出的水分。樹液流量和蒸騰量之間有很強的關聯(lián)性，通常理解是同一回事。但是，嚴格地說，它們是不同的，這體現(xiàn)在它們是如何被測量的。
SAP流量以L/hr（或每天、每周等）為單位進行測量。蒸騰量以每小時、每天、每星期等毫米（mm）為單位測量。
蒸散量=蒸騰量+蒸發(fā)量
蒸騰量以毫米為測量單位，可與降雨量以毫米計作比較。隨著時間的推移，降雨量（水輸入）應與蒸騰量（輸出）相匹配。如果蒸騰作用更高，通常是樹木作物的蒸騰作用，那么這種差異必須通過灌溉來彌補。
蒸發(fā)量（evaporation），蒸發(fā)量是指在一定時段內，由土壤或水中的水分經(jīng)蒸發(fā)而散布到空中的量。
1mm(降雨量)=1㎡地面1k
1mm(蒸騰量)=1㎡葉面積的1升樹液流量（水）
例如：在果園和葡萄園等有管理的樹木作物系統(tǒng)中，蒸發(fā)量與蒸騰量相比非常小。因此，為了簡化測量，通常忽略蒸發(fā)量，將蒸騰量取為平均蒸散量（ETo）。
莖流量傳感器廣泛應用
計算總流量
低液流和零液流速率
反向液流速率
夜間水分損失
根莖液流速度
貧瘠生態(tài)系統(tǒng)及干旱
徑向液體流速
葡萄藤的液流
莖流量傳感器 
技術指標
測量范圍：-200~+1000cm/hr(熱流速度)
分辨率：0.001cm/hr
準確度：±0.1cm/hr
探針尺寸：φ1.3mm*L30mm
溫度位置：外10mm，內20mm
針距：6mm
探針材質：316不銹鋼
溫度范圍：-30~+70℃
響應時間：200ms
加熱電阻：39Ω，400J/m
電源：12V DC
電流：空閑5mA, 測量<270mA
線纜：5m，*大60m
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