ldt with crimps vibration sensor/switch ldt0-028k piezo vibration rev 1 www.meas-spec.com 10/13/2008 1of 4 piezo film sensors high sensativity ac coupled laminated robust the ldt 0 - 028k is a flexible component comprising a 28 m thick piezoelectric pvdf polymer film with screen-printed ag-ink electrodes, laminated to a 0.125 mm polyester substrate, and fitted with two crimped contacts. as the piezo film is displaced from the mechanical neutral axis, bending creates very high strain within the piezopolymer and therefore high voltages are generated. when the assembly is deflected by direct contact, the device acts as a flexible "switch", and the generated output is sufficient to trigger mosfet or cmos stages directly. if the assembly is supported by its contacts and left to vibrate "in free space" (with the inertia of the clamped/free beam creating bending stress), the device will behave as an accelerometer or vibration sensor. adding mass, or altering the free length of the element by clamping, can change the resonant frequency and sensitivity of the sensor to suit specific applications. multi-axis response can be achieved by positioning the mass off center. the ldtm-028k is a vibration sensor where the sensing element comprises a cantilever beam loaded by an additional mass to offer high sensitivity at low frequencies. applications ? vibration sensing in washing machine ? low power wakeup switch ? low cost vibration sensing ? car alarms ? body movement ? security systems dimensions features ? solder tab connection ? both no mass & with mass version ? withstands high impact ? operating temperature: 0 o c to 85 o c ? storage temperature: -40 o c to 85 o c ? higher temperature version up to 125 o c available on a custom basis
ldt with crimps vibration sensor/switch ldt0-028k piezo vibration rev 1 www.meas-spec.com 10/13/2008 2 of 4 examples of properties four differen t experiments serve to illustrate the various prope rties of this simple but versatile component. experiment #1 ldt0 as vibration sensor - with the crimped contacts pushed through a printed-circuit board, the ldt0 was soldered carefully in place to anchor the sensor. a charge amplifier was used to detect the output signal as vibration from a shaker table was applied (using a charge amplifier allows a very long measurement time constant and thus allows the "open-circuit" voltage response to be calculated). small masses (approximately 0.26g increments) were then added to the tip of the sensor, and the measurement repeated. results are shown in table 1 and the overlaid plots in fig. 1. without adding mass, the ldt0 shows a resonance around 180 hz. adding mass to the tip reduces the resonance frequency and increases "baseline" sensitivity. table 1 : ldt0 as vibration sensor (see fig 1) added mass baseline sensitivity sensitivity at resonance resonant frequency +3 db frequency 0 50 mv/g 1.4 v/g 180 hz 90 hz 1 200 mv/g 4 v/g 90 hz 45 hz 2 400 mv/g 8 v/g 60 hz 30 hz 3 800 mv/g 16 v/g 40 hz 20 hz experiment #2 ldt0 as flexible switch - using a charge amplifier to obtain "open-circuit" voltage sensitiv ity, the output was measured for controlled tip deflections applied to the sensor (supported by its crimped contacts as described above). 2 mm deflection was sufficient to generate about 7 v. voltages above 70v could be generated by bending the tip of the sensor through 90 (see table 2, fig. 2).
ldt with crimps vibration sensor/switch ldt0-028k piezo vibration rev 1 www.meas-spec.com 10/13/2008 3 of 4 examples of properties (continued) table 2 : ldt0 as flexible switch (see fig 2) tip deflection charge output o/c voltage output 2 mm 3.4 nc 7 v 5 mm 7.2 nc 15 v 10 mm 10 - 12 nc 20 - 25 v max (90 ) > 30 nc > 70 v experiment #3 ldt0 electrical frequency response - when the source capacitance of around 480 pf is connected to a resistive input load, a high-pass filter characteristic results. using an electronic noise source to generate broad-band signals, the effect of various load resistances was measured and the -3 db point of the r-c filter determined (see table 3, fig. 3). table 3 : ldt0 electrical frequency response (see fig 3) (480 pf source capacitance) load resistance -3 db frequency 1 megohm 330 hz 10 megohm 33 hz 100 megohm 3.3 hz
ldt with crimps vibration sensor/switch ldt0-028k piezo vibration rev 1 www.meas-spec.com 10/13/2008 4 of 4 the information in this sheet has been carefully re viewed and is believed to be accurate; however, no responsibility is assumed for inaccuracies. furthermore, this information does no t convey to the purchaser of such devices any license under the patent rights to the manufacturer. measu rement specialties, inc. reserves the right to make changes without further notice to any product her ein. measurement specialties, inc. makes no warrant y, representation or guarantee regarding the suitab ility of its product for any particular purpose, no r does measurement specialties, inc. assume any liability arising out of the application or use of any product or circuit and specifically disclaims any a nd all liability, including without limitation consequential or incidental damages. typical parame ters can and do vary in different applications. all operating parameters must be validated for each cu stome r application by customers technical experts. measurement specialti es, inc. does not convey any license under its pate nt rights nor the rights of others. ordering information description part number ldt0-028k 1002794-0 ldtm-028k 1005447-1 north america measurement specialties, inc. 1000 lucas way hampton, va 23666 sales and customer service tel: +1-800-745-8008 or +1-757-766-1500 fax: +1-757-766-4297 technical support email: piezo@meas-spec.com europe meas deutschland gmbh hauert 13 44227 dortmund germany sales and customer service tel: +49 (0)231 9740 21 technical support tel: +49 (0)6074 862822 email: piezoeurope@meas-spec.com asia measurement specialties (china), ltd. no. 26 langshan road shenzhen high-tech park (north) nanshan district shenzhen, china 518107 sales and customer service tel: +86 755 3330 5088 technical support email: piezo@meas-spec.com table 4 : ldt0 clamped at different lengths (see fig. 4) length beyond clamp resonant frequency settling time (5 cyc) 20 mm (no clamp) 180 hz 28 msec 16 mm 250 hz 20 msec 11 mm 500 hz 10 msec 7 mm 1000 hz 5 msec experiment #4 ldt0 clamped at different lengths - using simple clamping fixture, the vibration sensitivity was measured (as in (1) above) as the clamp was moved to allow different "free" lengths to vibrate. the sensor may be "tuned" to suit specific frequency response requirements (see table 4, fig. 4).
mouser electronics authorized distributor click to view pricing, inventory, delivery & lifecycle information: measurement specialties: ? 1002794? 1005447-1 measurement specialties sensors: ? ldtm-028k? ldt0-028k/l
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