What accelerometer are you using? Depending on the bandwidth of the acc, you'll able or not to measure vibrations.

Does it work for vibrating tilt?

Dear Pradeepa,

Accelerometers are devices that have specific dynamic response such that they respond to vibrations with specific range of frequencies called the bandwidth as pointed out by Ryad and Mircea. In order to know the bandwidth of the accelerometer you have to revert to its DATASHEET. On the other side it is helpful to know the know the vibration range of vehicle.

Wish you success.

Ryad Chellali :ADXL335 Accelerometer we are using...

Thanks Dr.Abdelhalim we are using ADXL335 accelerometer currently its only working for tilt... how to set its bandwidth for vibration sensing...

Maybe you could try without Cx, Cy, Cz; if it works, you should then tune their values!

Hello Pradeepa,

Please read the ADXL335 datasheet carefully. Everything you needed is stated clearly there.

Best Luck!

Dear Pradeepa,

The bandwidth can be set by the capacitors connected to the outputs of the sensor.The following table for the bandwidth of the sensor versus the output capacitance values is taken from datasheet of your sensor. In the datasheet there is also a formula to calculate the capacitance for a given BW.

Table 4. Filter Capacitor Selection, CX, CY, and CZ

Bandwidth (Hz) Capacitor (μF)

1 4.7

10 0.47

50 0.10

100 0.05

200 0.027

500 0.01

Please try and report.

But an other important issue you may consider is the measuring and or display instrument. You have to use the proper ac measuring instrument. Can you tell us how do you measure the output voltage?

Wish you success.

the ADXL335 provides the 3 projections of the actual gravity vector (the absolute vertical) on an orthogonal frame attached to the sensor. You have to calibrate the sensor in order to have for instance (x=1, y=0, z=0). If you rotate the sensor you'll have portions of the graivity on the three axes. Say if you turn around the y axis by 180deg, the output of the sensor will be (x=-1,y=0,z=0). That's why you measure only the rotations. To have accelerations, use the derivative of the output signals (the variations of the signals). Assuming that you have only translations, the outputs give you the accelerations in the 3 directions. I don't know if you're using an arduino or equivalent, but it is very easy to write a code accordingly.

Let me know if it works

Thank you all i will try and report

i checked with various Capacitor but there is no change or no detection in vibration

Dear Pardeepa,

can you show us the acquired signals Vx, Vy and Vz with time?. I estimate that the vibration may be weak to be detected with this relatively insensitive acceleration sensor.It may be also that the dc value of the output voltage may be much greater than the AC value du to relatively weak vibration.If this is the case, you can use high pass filter with very low cut off frequency built by simple capacitor- resistor circuit with c= 10 uF and R about 100 kohm. The output is then amplified and displayed by an oscilloscope or it can be displayed directly by a sensitive instrument.

Please inform us.

wish you success.

Hi Abdelhalim

voltage values are

Vx=Vy=Vz=1.65

Hi Pradeepa,

What is the measuring instrument you used to measure such voltages. How is the sensor oriented? Please response as fast as possible to solve the problem.

Hi Abdelhalim

we have ADXL 335 accelerometer which is connected to telosB mote ADC and we have TinyOS code which gives the ADC output in the range of 2000... the value which is changing for tilt the device but there is no response in vibration... we are not much strong in electronics so that this much problem...

Hi Pradeepa,

Please check first the operation or you data acquisition system DAS by imputing a sinusoidal wave of known frequency and amplitude say 100 Hz and 1 volt and see the output of you your DAS. What is the sampling frequency of the DAS?.

You must be able to measure alternating voltage with you DAS. It seems for me till now that this is not the case as you DAS responses for static DC voltages and not for AC.

Dear Pradeepa:

I previously wrote this comment to you:But an other important issue you may consider is the measuring and or display instrument. You have to use the proper ac measuring instrument. Can you tell us how do you measure the output voltage?

Wish you success.

Please keep contact.

Hi Oradeepa,

what is the frequency of the vibration you want to measure?

Pradeepa,

I would suggest to Give a Try - Feed your vibration signals on the audio line input to your PC/laptop and then see if you are getting any response from your sensors or not. Keep the sampling rate as high as possible starting from 44kHz and up.

This will help you figure out exactly at what stage you have problem - i) is it the sensor or ii) the DAS that you are using is meant for DC or low frequency use only.

By the way, have you ever tried to monitor the sensor output on an oscilloscope? This might throw a light on what's happening and where!

Do send us update on the developments!

Best Luck!

The ADXL335 provides half of the reference voltage at 0 G and so you would get 1.65 V when powered with 3.3V.