SDT SHIELDED PIEZO SENSORS

9/2015

Page 2

INSTRUCTIONS

Using a double-sided adhesive tape, adhere the sensing element to the vibrating object. The adhesive tape

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 plastic lead attachment 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 they are permanent.

The leads can be connected directly into an oscilloscope or frequency analyzer with preferably, a

10 MΩ

impedance.

SENSOR OPERATION

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.

SDT1-028K Low Frequency Response

-36

-30

-24

-18

-12

-6

0

6

1

10

100

1000

10000

100000

Frequency (Hz)

R = 1 M Ohm

R = 10 M Ohm