(1) The dry and wet bulb humidity sensor uses two temperature sensing elements placed at the same measurement point. One of them is covered with a wet gauze, while the other remains dry. The difference in temperature between the two elements reflects the relative humidity of the air. These sensors can be thermistors or even simple heating packs. When there's a temperature difference, it causes a resistance change, which then generates an unbalanced voltage in a bridge circuit. This voltage output is proportional to the relative humidity, making it a reliable method for measuring humidity levels.
(2) The lithium chloride electric humidity controller works based on the principle that the electrical properties of lithium chloride change with moisture content. As the relative humidity in the air changes, the moisture absorbed by the lithium chloride coating alters its conductivity. This variation in current is amplified and used to control a solenoid valve responsible for humidification. When the desired humidity level is reached, the relay disconnects, closing the solenoid valve and stopping the spray. If the humidity drops below the set point by about 1%, the valve opens again, activating the humidifier to restore the correct level.
(3) The nylon (or hair) type pneumatic humidity transmitter utilizes the natural expansion and contraction properties of materials like nylon or human hair. A wetted element made from these materials stretches or contracts depending on the relative humidity. This physical change is converted into a mechanical signal, which can then be used to control a pneumatic system. However, this type of sensor is known for being complex to maintain, less sensitive compared to modern alternatives, and prone to aging or deformation over time. Due to these limitations, it is rarely used today.
Chloride Free Sandwich Board Substrate
Chloride Free Sandwich Board Substrate
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