MMA8452 sensivity

[marcick]

Hello,

sorry if this is a cross post. 

I asked two years ago support for the best configuration of this sensor to detect vehicle motion and you pointed me in the right direction with some application notes. 

But sometimes, if the vehicle start slowly or the ground is flat and regular, I detect the movement with a delay, 30 seconds or more and it’s too much. 

I will move to a new devices with higher sensitivity in a new project, but for the current projects I’m trying to understand if I can optimise the configuration and improve sensitivity. 

 I'm actually using this configuration. Is there anything I can do ?

$2A, [$18] ' 0x2A: CTRL_REG1 system control 1 register, Set device in 100Hz ODR, Standby
$1D, [$1E] ' 0x1D: Transient_CFG register, enable latch, Enable XYZ
$1F, [$01] ' 0x1F: TRANSIENT_THS register, set threshold to 1 counts
$20, [$05] ' 0x20: TRANSIENT_COUNT, set debounce 50mS
$2D, [$20] ' 0x2D: CTRL_REG4 register, enable transient interrupt
$2E, [$20] ' 0x2E: CTRL_REG5 interrupt configuration register, Route the Transient Interrupt to INT 1 hardware pin

[lisettelozano]

Hello Marco,

First please accept my apologies for the late response.

The MMA8452 is a 12-bit data resolution with a 1024 counts/g on 2g mode. A way to increase the resolution is by oversampling. One of the oversampling schemes of the data can be activated when MODS = 10 in register 0x2B which will improve the resolution of the output data only. The highest resolution is achieved at 1.56 Hz. However, this can increase power usage.

More details are shown in section 6 of the AN4075.  

Have a great day,

Paulina

[marcick]

Hello Paulina,

I have moved to a 14 bit sensor for a new project but I'm still interested to this topic to improve performances of my previous 8452 based design.

So, thank you anyway for your late reply. I'll study that application note.

Greetings from Italy

Marco