MMA7260Q

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#1
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I just got around to testing the sample I got from Freescale. The noise level on all 3 channels is extremely high. I'd be interested to know of others' experiences.

Ralph Hilton

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I am really disappointed to read that. I hopped that those chips would do better.

I have only tested my ADXL203CE samples from ADI. Latest generation of their Dual Axis Accelerometer line, the "precise" ones with analog output.

Compared to the MMA7260Q data sheet, the ADXL has slower turn-on time (20ms), no power-down mode, higher supply current (700-1100 μA), and a little better noise floor (1-6 mV rms).

I built a rather quick test circuit on a breadboard (no ground plane!) using a mega8 -which does not have a separate analog ground.
Output on a 20x4 LCD module (both axes, numeric and moving dot readout), 12-bit ADC oversampling (four successive readings, ADC_Clk 125KHz), no special software filtering, individual channel gain and offset corrections, and fast (look-up table based) arc calculations.

I was surprised to see a rock-steady LCD reading, under any angle:

Acceleration flickering: ±0.5mg. That's all!
Arc flickering: ±0.1°Deg; ±0.3°Deg worst case, at extreme angles (near 90°).

I was really impressed with the ADXL203CE. Almost no noise, despite the breadboard construction. Only the digitation error!

Giorgos

I hope for nothing; I fear nothing; I am free. (Nikos Kazantzakis)