Signal Conditioning in Accelerometer

[sdhawan]

accelerometer signal conditioning

Hi!
I am using accelerometer ADXL103 and for providing it a stabilized voltage I have used AD435 Reference(5V) .The whole setup is on a PCB but still I amgetting a lot of noise.CAn anybody suggest some SIGNAL CONDITIONING / filtering circuit for this. I want to sample data from accelerometer at 100SPS .
Thanks in advance

Salil

 

[nicleo]

accelerometer signal conditioner

I am using accelerometer ADXL103 and for providing it a stabilized voltage I have used AD435 Reference(5V) .The whole setup is on a PCB but still I am getting a lot of noise.CAn anybody suggest some SIGNAL CONDITIONING / filtering circuit for this. I want to sample data from accelerometer at 100SPS.

AD435 does not help if it's powered by noisy power supply. Make sure the power supply is clean enough, or you can reduce the noise by adding/choosing the right value/type of bypassing capacitor across Vs and COM pins of the accelerometer.

For most applications, a single 0.1 µF capacitor, CDC, will adequately decouple the accelerometer from noise on the power supply. However in some cases, particularly where noise is pre-sent at the 140 kHz internal clock frequency (or any harmonic thereof), noise on the supply may cause interference on the ADXL103/ADXL203 output. If additional decoupling is needed, a 100 Ω (or smaller) resistor or ferrite beads may be inserted in the supply line of the ADXL103/ADXL203. Additionally, a larger bulk bypass capacitor (in the 1 µF to 22 µF range) may be added in parallel to CDC.

The ADXL103 has provisions for bandlimiting the XOUT pin. Capacitor must be added at this pin to implement low-pass filtering for antialiasing and noise reduction... The accelerometer bandwidth selected will ultimately determine the measurement resolution (smallest detectable acceleration). Filtering can be used to lower the noise floor, which improves the resolution of the accelerometer. Resolution is dependent on the analog filter bandwidth at XOUT... The output of the ADXL103/ADXL203 has a typical bandwidth of 2.5 kHz. The user must filter the signal at this point to limit aliasing errors. The analog bandwidth must be no more than half the A/D sampling frequency to minimize aliasing. The analog bandwidth may be further decreased to reduce noise and improve resolution.

Possible to post the schematic of your circuit here? It will help us to understand your problem.

By the way, you may find some projects using ADXL103 at the following links:
**broken link removed**
https://www.sci-spot.com/Electronic/accelerometer.htm

 

[IanP]

accelerometer filtering

Depending on how you collect data, I would rather increase number of samples and then calculate evrage of 2, 3, 5 or more samples. That depends on your system: will it allow you to collect more than 100sps?
Simple filter (1 cap between output and GND) may also help...

 

[sdhawan]

bandwidth capacitor filters on accelerometers

Can you please explain the schematic of the circuit by which I ca take the average of 5/10 samples.Please also send some reference material on this.

 

[nicleo]

bandwidth accelerometer

Can you please explain the schematic of the circuit by which I ca take the average of 5/10 samples.Please also send some reference material on this.

I think you can still use the similar circuit to do what Ianp suggested, providing that the ADC's sampling rate in your system is 5 or 10 times higher than 100SPS. I assume you wish to update the reading every 0.01s. You can sample the output of accelerator at 500SPS. After 5 samples are recorded, you divide the sum of the samples by 5. By doing so, you can average out the noise. If the ADC's sample rate is just 100SPS, you can implement IanP's suggestion by performing 'moving average' method.

 

[sdhawan]

reduce noise in accelerometer signal

I was asking that how do we take the average of the samples?I have a 2kHZ ADC but don't know how to take average of the samples

 

[IanP]

signal conditioning description accelometers

Then how do you read bytes from your A/D? Where do the go?

 

[nicleo]

software filter noise accelerometer

I was asking that how do we take the average of the samples?I have a 2kHZ ADC but don't know how to take average of the samples

You can keep the data from ADC, e.g. 5 consecutive samples, in memory. Then, after you read 5 samples (probably can use a counter to trace), you sum up the values of 5 samples kept in the memory and divide the result by 5.

 

[brmadhukar]

accelerometer conditioner signal

Hi,
I guess you are using the accelerometer and gyroscope for some dead reckoning sort of application.
1) Make sure the voltage is stabilized as suggested in previous replies.
2) Keep the platform on which the devices are mounted very stable and horizontal. This should be done even if your final product moves. If there is a small tilt it introduces bias. If the platform is not stable it introduces noise. You may make the platform stable but there will be some tilit you need to remove it during signal conditioning either in software or FPGA.

Hope this helps,
B R M