Emfit S-series sensor is a fully shielded, low mass, thin, small area sensor. It typically consists of a sensing element constructed of elastic electret Emfit film and 2 layers of polyester film with screenprinted silver paste electrodes. Several other constructions are possible depending on application specific needs. Crimped connectors are used for connecting to electrodes.
Options available are a shielded cable with heat shrink tube over the joint and 50 microns acrylic adhesive available on one or both sides of the element.
Manufactured in rolls, width 580 mm, divided into rectangular areas with size of 290 x 300 mm, which are electrically connected to each other. Can be cut to shorter sensors. Custom lengths up to 50 meters are possible.
S-series sensors are manufactured in sheet laminating. These sensors are always custom made to given shape and measurements. Samples available: rectangular 10×20 mm, round 22 mm diameter.
Vibration/impact sensing, accelerometers, switches, machine monitoring, acoustic emission detection, contact microphone, acoustic pickup, pyrometer, etc.
Operating in a reciprocal fashion, changes in the thickness of the Emfit sensor generate a corresponding charge and hence, voltage to appear on the electrodes. The transducer behaves like an active capacitor, consequently, loading of the signal by the input impedance of the measuring device must be considered. Due to the thinness of the films, the associated capacitance can be sufficient to give adequate low frequency response into standard 1 MΩ loads, but the use of an X10 probe will extend the low frequency range by a decade.
For extremely low force change levels, some buffering may be desirable. For the majority of analysis work, this is unnecessary and the film can feed directly to the instrument. Again, the low mass contributed by the transducer is of major importance, and its non-resonate behaviour. Frequency response is inherently flat to over 20 KHz with only the R-C roll off at low frequencies distorting the profile.
Though it is responding to thickness change rather than strain, low signal levels may be generated by low frequency flexing, so a distinction must be made between the frequency response of the film for changes in its primary parameter (i.e., thickness) and its relative behaviour compared with, say piezoelectric sensors. The sensor has a flat response over a very wide frequency range, with resonant frequency points well above 20 KHz.
|Storage temperature||Ts||from -40 to +50||°C|
|Operating temperature ¹||Tr||from -20 to +70||°C|
|Sensitivity ²||Sq||25||pC/N||±20%||normal force|
|Relative permittivity||er||1,1||±10%||@ 10 kHz|
|Capacitance||C||22||pF/cm²||±5%||@ 1-150 kHz, EQV|
|Tensile strength at break, TD||535||N||±10%||ISO-527-1|
|Elongation at break, TD||20||%||±20%|
|Youngs modulus, TD||1,0||MPa||±50%|
|Operating force range||P||< 300||N/cm²|
1) Loss of sensitivity is < 20% after the following temperature cycles:
a) 11 hours at -20°C, 1 hour at +20°C, 11 hours at +70°C, 1 hour at +20°C, 28 cycles;
b) 1 hour at -20°C, 1 hour at +70°C, 10 cycles.
2) Sensitivity depends on the structure and the number of Emfit layers. Max sensitivity available is up to about 400 pC/N upon special order.