How to decrease the sensitivity of a sensor (accelerometer)
The accelerometer sensitivity can be set to +_/- 2g or +/- 8g - see below.

BUT what is the problem with the sensitivity being as it is?
Can you not just divide down the amplitude of the output to suit?

\ As long as the system does not "rail" under your tapping is it important that it has a large dynamic range? 



Digikey has these for $US10.90  - an utter bargain. 


L3GD20, ST MEMS motion sensor,  3-axis digital output gyroscope
LSM303DLHC, ST MEMS system-in-package featuring a 
3D digital linear acceleration sensor and a 
3D digital magnetic sensor




Sensitivity:

The user manual 36 page PDF says 


4.7 E-compass/accelerometer MEMS (ST MEMS LSM303DLHC)
The LSM303DLHC is an ultra-compact low-power system-in-package featuring a 3D digital
linear acceleration sensor and a 3D digital magnetic sensor. It includes a sensing element and an IC interface able to provide the measured acceleration to the external world through I2C serial interface.

The LSM303DLHC has dynamically user-selectable full scales of ±2g/±8g and is capable of
measuring acceleration, and a magnetic field full scale from ±1.3g to 8.1g with an output
data rate of 100 Hz or 400 Hz.
The STM32F303VCT6 MCU controls this motion sensor through the I2C interface.




• L3GD20, ST MEMS motion sensor, 3-axis
digital output gyroscope

• LSM303DLHC, ST MEMS system-in-package featuring a
3D digital linear acceleration sensor and a
3D digital magnetic sensor

• Ten LEDs:
– LD1 (red) for 3.3 V power on
– LD2 (red/green) for USB communication
– Eight user LEDS, LD3/10 (red), LD4/9
(blue), LD5/8 (orange) and LD6/7 (green)

• Two pushbuttons (user and reset)

• USB USER with Mini-B connector

• Extension header for all LQFP100 I/Os for
quick connection to prototyping board and easy
probing

Description
The STM32F3DISCOVERY helps you to discover
the STM32 F3 series Cortex-M4 mixed-signals
features and to develop your applications easily. It
includes everything required for beginners and
experienced users to get started quickly.
Based on the STM32F303VCT6, it includes an
ST-LINK/V2 embedded debug tool,
accelerometer, gyroscope and e-compass ST
MEMS, USB connection, LEDs and pushbuttons.
The STM32F3DISCOVERY discovery board does
not support STM32F313xx MCUs (1.65 V to
1.95 V power supply).
A large number of free ready-to-run application
firmware examples are available on
www.st.com/stm32f3discovery to support quick
evaluation and development.