良好的规格：您对RH规格的了解程度如何？

This week we discuss best practices in relative humidity specifications.

Check Device Specs + Know what to look for

这是一个靠近家的话题，因为Vaisala's history作为世界上最强大的电容薄膜聚合物传感器的创造者：腐殖质。现在，我们（通常）（通常）尽量不要使用此博客来吹嘘我们的出色产品，但是，正如所有湿度传感器的创建并不相等一样，所有产品规格也不一样。在我们的行业中，这有一些真正的争论点。

关于湿度校准的值对于理解湿度传感器的准确性和操作至关重要。事实是，这些价值通常在湿度仪器规范上歪曲或不存在。因此，本周，有可能有自己的号角的风险，我们将突出显示您需要了解的湿度仪器规格​​的要素，以使设备与操作环境，法规约束和应用程序要求相匹配。

漂移... RH测量的可悲现实

It's an immutable law of RH measurement. Sensors drift for the simple reason that they are "air breathers." Unlike temperature sensors, the internal structure of the humidity sensor must be in direct contact with the environment, which is constantly changing. Not only is the environment in flux, but it contains airborne contaminants that degrade the sensor over time. This is why, even if the calibration process were perfect (and sadly, it isn't), once exposed to the real world, the measurement accuracy inevitably decreases.

Terms to Know

查找有关设备或其校准过程的这些功能的信息：

可重复性：关闭ness of the agreement between the results of successive measurements of the same measurand carried out under the same conditions
非线性：校准曲线近似指定的直线的接近性，线性误差是校准曲线和指定的直线之间的绝对最大偏差。
滞后：设备的属性，该属性根据其输入值提供了不同的输出值，具体取决于已应用输入值的定向序列。磁滞误差是通过高档横向和整个范围内的倾斜横向获得的测量变量的两个校准曲线之间的最大偏差。简而言之，滞后是测量设备在测量更改后不完全返回其原始状态的趋势。在测量相对湿度时，它可能是错误的误差源。不幸的是，很少有数据表将滞后作为其准确性值的一个因素。规格表中未提及的磁滞可以被视为产品数据错误陈述。
校准不确定性：不确定性是与测量结果相关的参数，该参数表征了可以合理地归因于测量值的值的分散。它包括许多组件。例如，不确定性可能是具有指定置信度的标准偏差。

在湿度校准中，影响不确定性的一个因素是所有湿度室都有相关的不确定性，主要来源是温度不均匀。必须将其纳入测量设备的准确性规范。在湿度校准之前，Vaisala对每个数据记录仪进行了高准确的温度校准。然后，每个设备的测量温度能够补偿RH校准期间的腔室不均匀性 - 大大降低了这种误差源。控制误差的另一个元素是，使用Vaisala DL记录器，温度传感器就位于RH传感器旁边。这种接近度允许两个传感器“读取”相同的环境，从而消除其测量之间的差异。

辨别规格的艺术与科学

Product specifications, often one of the only ways decision makers can select a suitable system, must be explicit, easy-to-understand, and straightforward. All of the known influences and sources of error — calibration uncertainty, temperature effect, measurement resolution, and hysteresis — should be included in the accuracy value stated on any data sheet. If these values are not mentioned on a product data sheet, have they been included in that product's stated accuracy?

一种工作解决方案，以更好地评估

产品规格是设备采购决策过程中的关键要素。好的规格是明确的，易于理解且直接的。如果未在任何数据表上指定的价值，则应提及所有已知的影响和误差源 - 校准不确定性，温度效应，测量分辨率和磁滞 - 应提及。如果在产品数据表上未提及这些值，您如何确定它们已包含在该产品的精度中？

因此，如果您对设备附带的规格表不满意，这就是您要做的：要求校准不确定性陈述。If the accuracy values are not visible on the data sheet, check the calibration certificate. A professionally made calibration uncertainty calculation includes not only the uncertainty of the reference instrument or also factors related to the calibration process and unit under test. If the calibration is performed by an accredited laboratory, the uncertainty estimations are always inspected by qualified technical specialists. The quality of calculations varies strongly among other (standard) calibration providers.