【正文】 ue measured by the sensor and thus on the determined 吉林農(nóng)業(yè)大學(xué)本科畢業(yè)設(shè)計 2 timedependent characteristic is explained in more detail in the following. 3 Response characteristics and response time The response characteristics are defined by various parameters. These are: ? The actual response characteristics of the humidity sensor at constant temperature. (1) How quickly the sensitive polymer absorbs or releases moisture until equilibrium is reached (intrinsic response time) (2) How fast the entire system reaches humidity equilibrium (housing effect) ? The thermal response characteristics of the humidity sensor at a nonconstant temperature (3) The thermal mass of the sensor (4) The system39。 4. 與傳感器相關(guān)的系統(tǒng)熱質(zhì)量。但是，要到達(dá)距其還有 3%RH 6%RH的終端測量值還需要很長的時間。那樣會導(dǎo)致被測溫度比實際溫度高，而濕度則降低的結(jié)果 。 ? 殼體設(shè)計 (參考公式 1)應(yīng)考慮： ● 傳感器周圍空氣流通口的尺寸要盡可能地大，或者直接將傳感器置 于殼外 → 對流性最好封入套管內(nèi)時傳感器周圍的 “死區(qū) ”要盡可能地小， → 傳導(dǎo)性最小 。實際的校準(zhǔn)工作通常用以下兩 種方法（參見圖 2）： 1. 以 t2 時間對應(yīng)的測量值作為校驗參考基準(zhǔn)； 優(yōu)點 ： ? 到達(dá)終端值（例如 100%RH）所需要的測量時間明顯地縮短了，對應(yīng)于實際上的快速響應(yīng)傳感器。（濕度是溫度的函數(shù)，濕度會隨著溫度升高而降低，傳感器與被測環(huán)境之間的溫差會導(dǎo)致濕度測量誤差）更詳細(xì)的說明請見下一節(jié)。s thermal mass, which is thermally coupled to the sensor (. printed circuit board) (5) Heat sources in the direct surroundings of the sensor (electronic ponents) (1) and (3) are determined entirely by the sensor itself, (1) primarily by the characteristics of the sensitive polymer. (2) and (4) are primarily determined by the construction of the entire system (shape and size of housing andreadout circuitry). (5) is determined by heatemitting electronic ponents. These points will be discussed in more detail in the following. The intrinsic response time (1) Qualitatively, the response characteristics of capacitive humidity sensors look like the following (Fig. 1). Fig. 1: Typical and idealized response characteristics of capacitive humidity sensors (schematic) 吉林農(nóng)業(yè)大學(xué)本科畢業(yè)設(shè)計 3 Because these response characteristics are especially pronounced at high humidity values, an isothermal humidity jump from 40% to 100% was selected here for illustration. The desired ideal behavior of the sensor is indicated in blue. In practice, however, the sensor behaves according to the red line, approximately according to: RH t（ t） =(ES)*(1e )+S Here, the time span 1 is usually very short (typ. 1 – 30 min.), in contrast, the time span 2 is very long (typ. Many hours to days). Here the connection of measurement accuracy and response characteristics bees clear (t until RH=100% is reached). The value at t4 (Fig. 1) is considered to be an exact measured value. However, this assumes that