sdt1-028k Measurement Specialties, sdt1-028k Datasheet - Page 2

• Manufacturer Part Number: sdt1-028k
• Description: Sdt Shielded Piezo Sensors
• Manufacturer: Measurement Specialties

SDT Shielded Piezo Sensors Rev 1
SDT Shielded Piezo Sensors
Operating in a reciprocal fashion, changes in length generate a corresponding charge and hence, voltage to appear on the
electrodes of the film. 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 use of an X10 probe will extend the low
frequency range by a decade. For extremely small devices and low frequency vibration levels, some buffering may be
desirable. For the majority of analysis work, this is unnecessary and the film can feed directly to the instrument.
The low mass contributed by the transducer is of major importance, and its non-resonant behavior. Frequency response is
inherently flat into the MHZ region with only the R-C roll off at low frequencies distorting the profile. Since it is responding to
strain rather than acceleration, high 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., strain) and its relative behavior
compared with, say piezoelectric accelerometers.
The response of the sensor to strain enforces its likeness to a strain gauge, but with much higher output. The sensor
performs well at low frequencies where displacement is large and acceleration low, as well as at high frequencies where
displacement is small and acceleration high. The sensor has a flat response over a very wide frequency range, with resonant
frequency points above 10 MHZ.
Using a double-sided adhesive tape, adhere the sensing element to the vibrating object. The adhesive tape should
have a thin and non-foam type carrier. A double-sealed tape, such as 3M† 444, works well.
Clean off the surface of the object upon which the sensor is to be placed, removing any foreign particles such as dirt,
dust, grease, etc. Then apply the adhesive tape to the clean surface. Next, adhere the SDT1-028K to the adhesive by
attaching the end of the sensor element first and smoothing out the element (avoiding any creases or air bubbles)
towards the lead attach.
The adhesive must continue out and hold down the lead attached housing as well, to prevent errant results. Similarly, it
is recommended that the wire be taped down in some instances (this can be done with masking tape in a designated
position).
If the sensor is to be used in an environment above 45°C [114°F], then a different adhesive system is recommended
since the double sided tape can become soft and affect the sensor's ability to detect vibration. Cyanoacrylate or a five-
minute epoxy are useable, but are permanent.
The leads can be connected directly into an oscilloscope or frequency analyzer with preferably 10 MΩ impedance.
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SDT1-028K Low Frequency Response
10
sensor operation
www.meas-spec.com
instructions
Frequency (Hz)
100
2 of 3
1000
Element with Shielded Cable
10000
100000
R = 1 M Ohm
R = 10 M Ohm
05/12/2009