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Psychrometer sensors type FEP to measure the psychrometric difference and air temperature to determine relative air humidity. FEP 1 2 3 4 5 6 Psychrometer-sensor type FEP2 Pt100 Pt100 Pt100 1.dry temperature wet temperature 2.dry temperature Connection diagram Description The FEP psychrometer sensor unit consists of two or three Pt100 temperature sensors connected to a water tank and a humidifying wick. The sensors are arranged horizontally above the water tank filled with water. A cotton wick which covers the lowest temperature sensor rises up with its free end into the water tank, constantly absorbs water, and produces the moistening important for psychrometric measuring. Psychrometric measuring is based on the principle that the surface of the temperature sensor (wet-bulb temperature) - which is kept moist - cools down by evaporation. Using the air temperature which is measured simultaneously (dry-bulb temperature), the partial pressure of the water vapour in the air can be calculated by applying the Sprung formula (see separate description). Psychrometer tables or diagrams give information on the relative humidity. Psychrometer wick The quality of the psychrometer wick is equally as important for a good measuring result. Ideally, distilled water should be used for the humidifying process. In a practical application, and particularly during continuous measuring or regulation, water is taken mainly from the mains using the flow-and-rinse principle. It should be noted, however, that calcareous water causes the wick to become incrusted, so that it loses its absorbent property and the measuring result becomes distorted. Ventilation Adequate ventilation of the humidity temperature sensor is an essential requirement for flawless psychrometric measuring. Ventilation at an air speed of more than 2 m/sec is sufficient. A higher air speed does not have any appreciable influence on the measuring result. An air speed below 2 m/sec can have a decisive influence on the measuring result as there is insufficient evaporation and therefore no latent heat at this air speed. The wet- bulb temperature is too great and the relative humidity is too high. Output Input Technical data sensor ...................................... resistance thermometer Pt100 in accordance with1/3DIN EN 60751 cl.B dry-temperature sensor ............................................. 1(2) x Pt100 wet-temperature sensor ................................................. 1 x Pt100 max. allowable power............................................................. 3mA connection .................. screw terminals in the connection head type of protection ..................................................................... IP54 housing ......................... complete fitting made of highgrade steel, item no. 1.4571 allowable ambient temperature ............................. -10...+100 °C working temperature ............................................... -10...+100 °C ! from 0°C to -10°C employ the psychrometric constant of ice, see description psychrometer mounting position ......................................................... horizontal installation depth type FEP1 .............................................130mm type FEP2 ........................................... 210mm wick ..................................................................... absorbent cotton weight ..................................................................................... 0.8 kg electromagnetic compatibility EMC resistance to interference ......................... ref. EN 50 082-2 interference emission ............................... ref. EN 50 081-2 "subject to technical modifications" Gall Gall Gall Gall Galltec tec tec tec tec Mess- und Regeltechnik GmbH MELA MELA MELA MELA MELA Sensortechnik GmbH D-71145 Bondorf . Germany D-07987 Mohlsdorf (Thüringen) . Germany Tel. +49 (0)7457-9453-0 . Fax +49 (0)7457-3758 Tel. +49(0)3661-62704-0 . Fax +49(0)3661-62704-20 E-Mail: [email protected] . Internet:www.galltec.de E-mail:[email protected] . Internet: www.melasensor.de This information is based on current knowledge and is intended to provide details of our products and their possible applications. It does not, therefore, act as a guarantee of specific properties of the products described or of their suitability for a particular application. It is our experience that the equipment may be used across a broad spectrum of applications under the most varied conditions and loads. We cannot appraise every individual case. Purchasers and/or users are responsible for checking the equipment for suitability for any particular application. Any existing industrial rights of protection must be observed. The perfect quality of our products is guaranteed under our General Conditions of Sale. Issue : May 2001 valid until 31.12.2006 FEP_E. Subject to modifications, current version available at www.galltec.de. This issue supersedes all previous technical leaflets.
