Impossibility to change the rate of the accelerometer

Question

I have to collect accelerometer data from my Android phone, so I have made a little program to do that.

After some tests, I have found that my Nexus S accelerometer's rate is always 50 values per second when the phone is active, and 6 values per second when it is asleep (with a PARTIAL_WAKE_LOCK), whatever the rate I ask for (NORMAL, UI, GAME or FASTEST).

So I decided to install an application found on the Internet which tests the rate of the accelerometer : http://samoht.fr/tuto/accelerometers-frequency-on-android-with-code

But I got the same "error" : whatever the rate I ask for, it is always 50 values per second when the phone is active.

I don't understand why my phone behaves this way. Is it a problem :

• related to the Nexus S ?
• specific to my phone ?
• related to Android 4 ?

EDIT : I have tested the program on another Nexus S (Android 4), and I have the same problem. So it seems to eliminate one of the possibilities listed above: it is not related only to my phone.

Answer 1

I have performed some tests on different smartphones. Here are the results:

Samsung Galaxy Teos
-------------------
* When awake
    Normal: 4.17 Hz
    UI: 8.43 hz
    Game: 16.93 Hz
    Fastest: 109.42 Hz

* When asleep
    The phone sends null values (0), whatever the mode I chose


Samsung Nexus S
---------------
* When awake
    Normal: 49.51 Hz
    UI: 49.51 hz
    Game: 49.51 Hz
    Fastest: 49.51 Hz

* When asleep
    6.06 Hz, whatever the mode I chose

LG Nexus 5
----------
* When awake
    Normal: 15.39 Hz
    UI: 15.4 Hz
    Game: 50.05 Hz
    Fastest: 196.74 Hz

* When asleep
    Normal: 4.96 Hz
    UI: 15.41 Hz
    Game: 50.12 Hz
    Fastest: 198.53 Hz

LG Nexus 4
----------
* When awake
    Normal: 15.75 Hz
    UI: 15.74 Hz
    Game: 48.86 Hz
    Fastest: 195.85 Hz

* When asleep
    Normal: 5.5 Hz
    UI: 15.74 Hz
    Game: 49.16 Hz
    Fastest: 196.75 Hz


Samsung Galaxy Nexus
--------------------
* When awake
    Fastest: 125 Hz

* When asleep
    It sends data


Samsung Galaxy Note 2
---------------------
* When awake
    Fastest: 100 Hz

* When asleep
    The phone does not send anything


Samsung Galaxy S3 and S3 Mini
-----------------------------
* When awake
    Fastest: 100 Hz

* When asleep
    Fastest: 100 Hz


HTC Wildfire
------------
* When awake
    Normal: 4 Hz
    UI: 12 hz
    Game: 22.2 Hz
    Fastest: 38.40 Hz

* When asleep
    The phone does not send anything, whatever the mode I chose


HTC Desire
----------
* When awake
    Normal: 4.36 Hz
    UI: 11.9 hz
    Game: 23.3 Hz
    Fastest: 47.27 Hz

* When asleep
    The phone does not send anything, whatever the mode I chose

Note that the tests have been performed using a partial wake lock. Without it, the Nexus S provides no data at all when it is asleep.

There is also a useful list of smartphones which accelerometers send (or not) compatible data when asleep: http://www.saltwebsites.com/2012/android-accelerometers-screen-off