08濕度傳感器系統(tǒng)畢業(yè)論文中英文資料外文翻譯文獻(xiàn)(編輯修改稿)
2025-04-08 10:08 本頁(yè)面
【文章內(nèi)容簡(jiǎn)介】 et periods in outdoor operation), an exact measurement result is obtained (cf. Fig. 2). Disadvantage: ? For a humidity jump like in Fig. 1, the sensors very quickly deliver the measured value at t2, but reaching a stable end value (about 36% higher) takes a long time (apparent longer response time)(cf. Fig. 2). In order to take into account both approaches optimally, the measured values at t3 (cf. Fig. 1) are used as the calibration reference by Sensirion AG. 吉林農(nóng)業(yè)大學(xué)本科畢業(yè)設(shè)計(jì) 4 Fig. 2: Response characteristics of different humidity measurement systems The housing effect on the response time (2) Here, two types of transport phenomena play a deciding role: ? Convection: For this very fast process, the air, whose humidity is to be determined, is transported to the sensor by means of ventilation. ? Diffusion: This very slow process is determined by the thermal, molecular selfmotion of the water molecules. It occurs even in stationary air (., within a housing), but leads to a long response time. In order to achieve favorable response characteristics in the humidity measurement system, the very fast convection process must be supported by large housing openings and the slow diffusion process must be supported by a small housing around the sensor (small dead volume) with stationary air reduced to a minimum. The following applies: Thermal effects (3), (4), and (5) Because the total thermal mass of the humidity measurement system (sensor + housing) has a significant effect on its response time, the total thermal mass must be kept as low as possible. The greater the total thermal mass, the more inert the measurement system bees thermally and its response time, which is temperaturedependent, increases. In order to 吉林農(nóng)業(yè)大學(xué)本科畢業(yè)設(shè)計(jì) 5 prevent measurement errors, the sensor should not be mounted in the vicinity of heatgenerating ponents. 4 Summary – what should be taken into account when designing a humidity measurement system In order to achieve errorfree operation of a humiditymeasurement system with response times as short as possible, the following points should be taken into account especially for the selection of the sensor and for the design of the system. ? The selection of the humidity sensor element. It should ● be as small as possible, ● have a thermal mass that is as low as possible, ● work with a polymer, which exhibits minimal fluctuations in measured values during the time span 2(cf. Fig. 1)。 testing gives simple information on this condition, ● provide calibration, which corresponds to the requirements
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