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概览
237 通过确定传感器表面的电阻值来测量叶面湿度。表面越湿电阻值越低。主要用来判定叶片的相对于干燥的潮湿时间百分比。
优势与特点
- 传感器发运时没有上漆，客户可以选择合适的表面以最适合他们的应用
- 模仿叶片的特征
图像
相似产品
技术说明
237 包括一个带有隔行镀金finger的电路板。传感器上的冷凝会降低finger之间的电阻值，数据记录器可以测量出来。
水滴必须同时接触两个finger，才能改变传感器的电阻值。考虑季节因素，237专门采用平滑的乳胶漆外壳，利于水滴下滑。涂层的颜色和类型可影响传感器的性能。Campbell Scientific提供无涂层的传感器便于用户根据需要为传感器上色。恰当的染色应与一种树叶的颜色相
校准
应该测定传感器在湿润/干燥的过渡点的电阻值。没有涂层的传感器，湿润/干燥过渡时电阻值会发生剧烈的变化。通常会在50至200 kohms之间变化。带涂层的传感器会有定义不清的过渡，通常发生在20kohms到1,000 kohms之上。为了得到最佳结果，传感器应该置于现场校准，这是因为过渡点会因地点和植被的不同而变化。
产品规格
| Resistance at Wet/Dry Transition |
|
| Operating Temperature Range | 0° to 100°C |
| Short-Term Survivability Temperature Range |
-40° to +150°C Sensor may crack when temperature drops below -40°C. |
| Painting | Sensor is shipped unpainted so customer can choose appropriate surface finish to best match the application. |
| Hole Spacing | 6.73 cm (2.65 in.) |
| Hole Diameter | 0.54 cm (0.213 in.) |
| Dimensions | 7.6 x 7.1 x 0.64 cm (3.0 x 2.75 x 0.25 in.) |
| Weight | 91 g (3 oz) with 3.05 m (10 ft) cable |
兼容性
Please note: The following shows notable compatibility information. It is not a comprehensive list of all compatible products.
数据采集器
| Product | Compatible | Note |
|---|---|---|
| CR1000X | ||
| CR300 | ||
| CR3000 (retired) | ||
| CR310 | ||
| CR350 | ||
| CR6 | ||
| CR800 (retired) | ||
| CR850 (retired) |
Additional Compatibility Information
Data Logger Considerations
The 237 requires one single-ended analog input and one switched excitation channel for measurement.
相关技术文档
常见问题解答
237-L: 13
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Paint only with a flat latex paint. Usually, a high-quality, white, flat latex paint is used with a tiny amount of pigment.
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Approximately 0.9 mm.
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Variable, but always negligible. The theoretical maximum for each measurement is 5000 mV at 5 µA for less than 3 ms.
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Yes. The thermal characteristics of the 237-L are probably different from those of any surrounding objects, including leaves. Consequently, the 237-L will dry at a rate different from surrounding objects, including leaves.
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The mounting method used depends on the application. In plant canopies, consider mounting the 237-L so that it receives the least amount of solar radiation at noon. This means tipping the sensor, electrodes up, so that its sensing surface is parallel to the plane of the ecliptic. Tipping the sensor also minimizes the chance of water puddling on its surface.
On non-living surfaces, such as a man-made structure, consider mounting the 237-L flat against a flat surface on the shady side. This will cause the 237-L’s thermal characteristics to be more similar to those of the surface being studied.
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The 237-L is not designed to be used as a conductivity sensor. To our knowledge, a few people have tried this but have been unsuccessful.
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Only in the most basic sense. The signal output from the 237-L can only be interpreted as an indication of the presence of a conductive material bridging the two electrodes on its surface. If the circuit is open (infinite resistance or zero conductance), there is no conductive material. If the circuit is closed, there is conductive material.
The primary use of the 237-L is to indicate the presence of free water on the surface of surrounding objects. The thermal characteristics of the 237-L are probably different from those of any surrounding objects, including leaves. Consequently, the 237-L will dry at a rate different from surrounding objects, including leaves. Data from the 237-L are only interchangeable from measurement site to measurement site if the following are true:
- Each 237-L is prepared and maintained in the same way.
- Each 237-L is mounted in nearly identical environments.
Plant disease researchers found that if a 237-L sensor was placed in a plant canopy at a consistent position, with a consistent coating of a spreading material on its surface (that is, paint), they could estimate when free water was in the plant canopy. From this discovery, they were able to formulate disease emergence models. The resulting models tolerate significant deviation in moisture-presence data. Even so, use of a different spreading material, or difference in sensor positioning, may invalidate the data.
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No. The sensor signal can only be interpreted as either wet or dry.
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Both leaf wetness sensors are compatible with all Campbell Scientific data loggers. However, the 237-L is often used in large legacy networks that rely on the 237-L for data continuity. The 237-L does require painting and field calibration, whereas the LWS does not.
案例研究
The Delaware Environmental Observing System (DEOS) is a real-time system dedicated to monitoring environmental conditions......阅读更多