HD3817T / HD38V17T series - Absolute Humidity Transmitters The HD3817T… and HD38V17T… aredouble absolute humidity and temperature active transmitters with 4…20mA current or 0…10Vdc voltage outputs, respectively. Absolute humidity is the ratio between the mass of water vapour and the measured volume of air, and is expressed in g/m³. The transmitters of the HD3817T… family may be used in materials humidity control during a drying process. When the materials are dried through heating or a hot air flow, the air absolute humidity increase is directly proportional to the quantity of water lost by the materials. A control system measuring absolute humidity, can maintain a certain humidity level by injecting vapour or water spray in the environment, if needed. Generally, these transmitters are employed in the chemical, textile, food industry, in the production and storage of paper, in the drying of wood, even with high temperatures and wide humidity excursions. The type of sensor used is immune to most physical and chemical contaminants. The maximum working temperature is 200°C: This makes these instruments particularly suitable to heavy industrial applications where the traditional capacitive sensor cannot be used. The response time is fast, as well as the recovery time from saturation. The maximum measurement ranges are: 0…130 g/m³ for absolute humidity and 0…200°C for temperature: the instruments come out of the factory with the 0…60g/m³ and 0…200°C standard ranges. When placing the order, different ranges both for absolute humidity and temperature can be requested but within the set limits. The standard power supply is 24VAC. On request, 115VAC or 230VAC versions are available. The probe is made of stainless steel and has a 20µm sintered bronze filter. The case is in polycarbonate with an IP66 protection degree.