Gall
tec Mess- und Regeltechnik GmbH MELA Sensortechnik GmbH
Galltec
D-71145 Bondorf . Germany
Tel. +49 (0)7457-9453-0 . Fax +49 (0)7457-3758
E-Mail: [email protected] . Internet:www.galltec.de
D-07987 Mohlsdorf (Thüringen) . Germany
Tel. +49(0)3661-62704-0 . Fax +49(0)3661-62704-20
E-mail:[email protected] . Internet: www.melasensor.de
Psychrometer sensors
type FEP
to measure the psychrometric difference and air temperature
to determine relative air humidity.
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.
FEP
Output
Input
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 wetbulb temperature is too great and the relative humidity
is too high.
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.
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.
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"
Connection diagram
Psychrometer-sensor
Pt100
1
type FEP2
Pt100
2
1.drytemperature
3
Pt100
4
2.drytemperature
5
6
wet temperature
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.
FEP_E page 2
Dimension diagram
Front view
Back view
Side view
Mounting drawing
Connection
screw terminals in the connection head