挑选湿度传感器比挑选其它类型的传感器所需求考虑的内容更多。
首要,有必要挑选传感器的结构,使灵敏元件的规定的丈量时刻之内达到所测流体或被测外表的温度。
在大多数情况下,对温度传感器的选用,需考虑以下几个方面的问题:
(1)被测目标的温度是否需记载、报警和自动控制,是否需求远距离丈量和传送。
(2)测温规模的巨细和精度要求。
(3)测温元件巨细是否恰当。
(4)在被测目标温度随时刻改变的场合,测温元件的滞后能否习惯测温要求。
(5)被测目标的环境条件对测温元件是否有损害。
湿度传感器的挑选主要是依据丈量规模。当丈量规模估计在总量程之内,可选用铂电阻传感器。较窄的量程一般要求传感器有必要具有相当高的根本电阻,以便取得足够大的电阻改变。热敏电阻所供给的足够大的电阻改变使得这些灵敏元件十分适用于窄的丈量规模。如果丈量规模相当大时,热电偶更适用。最好将冰点也包含在此规模内,因为热电偶的分度表是以此温度为基准的。已知规模内的传感器线性也可作为挑选传感器的附加条件。
响应时刻一般用时刻常数表示,它是挑选传感器的另一个根本依据。当要监视贮槽中温度时,时刻常数不那么重要。但是当运用过程中有必要丈量振荡管中的温度时,时刻常数就成为挑选传感器的决定因素。
动态温度的丈量比较复杂,只要经过反复测验,尽量挨近地模拟出传感器运用中经常发作的条件,才干取得传感器动态性能的合理近似。
The selection of humidity sensors is more than the need to select other types of sensors.
First of all, it is necessary to select the structure of the sensor so that the prescribed measurement time of the sensitive element can reach the temperature of the measured fluid or the measured surface.
In most cases, the selection of temperature sensors needs to consider the following aspects:
(1) whether the temperature of the target to be recorded, alarm and automatic control, whether the need for remote measurement and transmission.
(2) the size and accuracy requirements of temperature measurement scale.
(3) whether the temperature measuring element is big or small.
(4) when the temperature of the target is changed with time, can the temperature sensor's hysteresis be used to the temperature measurement requirement?.
(5) whether the environmental condition of the target is harmful to the temperature measuring element.
The selection of humidity sensor is mainly based on measurement scale. When the measurement scale is estimated within the total range, the platinum resistance sensor can be selected. Narrow ranges generally require sensors to have very high fundamental resistance so that large enough resistance changes can be achieved. The large enough resistance of the thermistor makes the sensors very suitable for narrow measurement scales. Thermocouples are more suitable if the measurements are quite large. It is better to include the freezing point in this scale, because the scale of the thermocouple is based on this temperature. The sensor linearity in the known scale can also be used as an additional condition for the selection of sensors.
The response time is usually expressed by a constant of time, and it is another fundamental basis for selecting sensors. When the temperature in the tank is monitored, the time constant is not so important. But when it is necessary to measure the temperature in the oscillating tube, the time constant becomes the decisive factor in choosing the sensor.
The dynamic temperature measurement is more complex, as long as after repeated tests, try to simulate the sensor application conditions often occur, can obtain the reasonable approximate dynamic characteristics of sensor.
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