The POLYGA® fibre offers an extraordinary long-term stability and a high accuracy in high humidity ranges. The fibre is absolutely water resistant and washable.
The Polyga® humidity measuring element consists of several synthetic fabric bands each with 90 individual fibres with a diameter of 3 µm each. In their untreated state, the synthetic fibres are not hygroscopic – their hygroscopic properties are acquired by means of a special process which allows the synthetic fibres to absorb moisture. The molecular structure of the individual fibres is arranged lengthways.
When water is absorbed, the molecular chains alter, the outward result being a change in length. A loss of water has a converse effect on the fibre. If the fibre is in equilibrium with the air humidity, there is neither absorption nor a loss of water. The length at this point serves as a gauge for the relative humidity. If the measuring element is exposed to an air humidity of 100%rh, a film of water forms on the surface of the element (dew point).
The physical effect is one as if the measuring element had been immersed in water. The measuring element is saturated. An ideal fixed point is thus attained for adjusting or controlling the sensors. The measuring element is waterresistant. Once administered to the Galltec measuring element, the hygroscopic properties remain stable, the sensitivity remaining until it becomes destroyed by extraneous influences. Regeneration as with fine-measuring elements is not necessary, but does not cause any harm.
In order to maintain their long-term stability, it is important that the measuring elements undergo a special ageing process, details of which cannot be given
here.
Due to the law of diffusion, there is a time delay before the fibres are saturated during water absorption. This is a decisive factor when determining the reaction time. Thus, for one individual fibre with a diameter of 3 µm, a short saturation time (several se-conds) can be measured. Empirical investigations show that bundled or woven fibres, as are used here in the Galltec sensor, give rise to a longer period prior to saturation. This is because the individual fibres impede each other during water absorption and/or water loss, and the ensuing humidity does not register until later. Measurements have shown that, at a wind speed of 2m / sec. the half-life period is 1.2 mins. This represents an effective period of approx. 30 – 40 mins.
The expanding action (predominantly lengthways) of the fibres is picked up by means of an electronic sensing system and converted by integrated signal preprocessing into standardised signals
0..20mA or 4..20mA or 0…10V. The fan-shaped measuring element, which faces outward from the housing, is protected by a perforated sensor tube. The sensors are designed for pressureless systems. The unit should be installed in a location where condensation cannot enter into the housing. A preferred position would be ”sensor vertically down” or ”sensor horizontal”. In these positions, a cover plate with a 0.8 mm diameter hole will prevent water from entering. The TFG80 range of sensors have built-in temperature sensors (mainly Pt100) for simultaneous measurement of temperature. Temperature readings are converted likewise into standardised signals 0..20mA or 4..20mA or 0..10V.
80º C is given as the maximum temperature value. Higher temperatures can only be tolerated for a short period of time. The eventual result is a change in the molecular structure which causes a constant error. The maximum temperature of 80º C only applies, however, if no harmful substances (acids, solvents etc.) are present in the medium.
Galltec sensors are adjusted correctly at a room temperature of 23ºC and 50%rh at a mean air pressure corresponding to 430m NN. If, however, a further adjustment is necessary, the following procedure should be adhered to:
For more information download the Humidity Sensor FG80 (r.h.) Humidity Temperature Sensor TFG80 – Datasheet
The expanding action (predominantly lengthways) of the fibres is picked up by means of an electronic sensing system and converted by a potentiometer into a resistance signal. The fan-shaped measuring element is protected in the housing. The sensors are designed for pressureless systems. The unit should be installed in a location where condensation cannot enter into the housing. The mounting position is optional, preferably with ventilation slots at right angles to direction of airflow. The TFG120 sensors have built-in temperature sensors (mainly Pt100) for simultaneous measurement of temperature.
The room sensor should be mounted on a vertical wall about 1.5m above the floor. Ensure that the housing can not be deformed because of rough walls. Do not fit above radiators, near windows or doors, on areas exposed to intense vibration or direct sunlight, exterior walls or chimneys. Under no circumstances must the sensors be mounted into a wall or niche. The sensors should be protected from dripping water or splashes. Ensure that no external air can flow into the interior of the housing via the concealed cable lead. Do not use a silicon sealing compound to seal the cable lead. The sensors should be mounted such that air in the room can flow upwards unimpeded through the ventilation slots in the housing cover.
50º C is given as the maximum temperature value. Higher temperatures can only be tolerated for a short period of time. The eventual result is a change in the molecular structure which causes a constant error. The maximum temperature of 50º C only applies, however, if no harmful substances (acids, solvents etc.) are present in the medium. The temperature coefficient as well as the self-heating may vary according to the location and the application (especially with sensors where electronic and measuring system are integrated in one housing).
For more information download the Humidity Sensor FG120 (r.h.) Humidity Temperature Sensor TFG120 – Datasheet
A special process gives the fibre in this sensor hygroscopic properties. The measuring element absorbs and desorbs humidity. The swelling effect, which is predominantly in a lengthways direction, is sensed by means of a suitable fine loop resistor. The coil and slide contact of the fine loop resistor consist of a gold wire alloy. Minimum contact resistance and safe contact are guaranteed. The fan shaped measuring element is protected by a perforated sensor tube. The modules are designed for pressureless systems. Pt100 resistance temperature sensors are mounted in the TFM80H module for simultaneous temperature acquisition. Other temperature measuring systems can be supplied on request.
The measuring element is maintenance free when the surrounding air is clean. Agents that are corrosive and contain solvents, depending upon the type and concentration of the agent, can result in faulty measurements and cause the measuring element to break down. Substances deposited on the sensor are damaging as they eventually form a water-repellent film (this applies to all humidity sensors with hygroscopic measuring elements).
Such substances are resin aerosols, lacquer aerosols, smoke deposits etc. The water-resistant property of the Galltec sensors allows for cleaning using water. Solvents cannot be used for this purpose. A light-duty detergent is recommended. Any detergent residue should, however, always be thoroughly washed out. A special process ensures that Galltec sensors have good long-term stability. Regeneration is not necessary, but is also not harmful. Humidity module type FM80H with resistance output to determine relative air humidity, in builtin design. Humidity-Temperature module type TFM80H with resistance output to determine relative air humidity and temperature, in built-in design. Description of the module The humidity measuring element, produced by Galltec under the name Polyga®, consists of several synthetic fabric bands each with 90 individual fibres with a diameter of 3 m.
A special process gives the fibre hygroscopic properties. The measuring element absorbs and desorbs humidity. The swelling effect, which is predominantly in a lengthways direction, is sensed by means of a suitable fine loop resistor. The coil and slide contact of the fine loop resistor consist of a gold wire alloy. Minimum contact resistance and safe contact are guaranteed. The fan shaped measuring element is protected by a perforated sensor tube. The modules are designed for pressureless systems. Pt100 resistance temperature sensors are mounted in the TFM80H module for simultaneous temperature acquisition. Other temperature measuring systems can be supplied on request.
ATTENTION: No warranty will be guaranteed when inner parts of the device have been handled.
The average deviation of temperature behaviour is 4%rh. the sensors are adjustd at 23°C. The following chart shows the temperature behaviour of the Polyga® measuring elements.
80º C is given as the maximum temperature value. Higher temperatures can only be tolerated for a short period of time. The eventual result is a change in the molecular structure which causes a constant error. The maximum temperature of 80º C only applies, however, if no harmful substances (acids, solvents etc.) are present in the medium.
For more information download the Humidity Module FM80 (r.h.) Humidity-Temperature Sensors TFM80 – Datasheet
