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Body Position Sensor Basics

body position sensor accelerometer patient monitoring sensor medical device

This article explains the basics, features, and manufacturers of body position sensors. A 3-axis digital accelerometer IC can be used as a body position sensor.

Introduction

Monitoring the positions of elderly and disabled individuals is crucial. Accelerometer sensors serve this purpose effectively. A body position sensor monitors five different positions: standing, sitting, supine (lying face upwards), inclined, left, and right.

Patients with conditions like sleep disorders and restless leg syndrome also require position monitoring during treatment. Analyzing movements during sleep can help identify sleep quality and irregular sleeping patterns. These sensors can also prevent falls or fainting by monitoring a patient’s position when they’re alone.

What is a Body Position Sensor?

Definition: A sensor, such as a 3-axis accelerometer, used to determine a patient’s position (standing, sitting, supine, inclined, left, and right).

These accelerometer-based sensors can be easily interfaced with microcontroller boards like Arduino Uno or Arduino Mega.

Body Positions

Features of a Body Position Sensor

The features/specifications of a 3-axis accelerometer (e.g., ADXL345 manufactured by Analog Devices) include:

  • Functions as a 3-axis digital accelerometer
  • Selectable range: ±2g / ±4g / ±8g / ±16g
  • Up to 13-bit resolution (resolution increases with the “g” range)
  • I2C and SPI serial interfacing
  • Ultra-low power consumption (23 µA in measurement mode and 0.1 µA in standby mode at 2.5V)
  • 32-level FIFO storage

Body Position Sensor Manufacturers

The following table lists features and part numbers from different body position sensor manufacturers:

ManufacturersFeatures with Part Number
Analog DevicesPart Number: ADXL345. Features: As mentioned above.
STMicroelectronicsPart Number: LIS2DE12. Ultra-low power consumption down to 2 µA. ±2g / ±4g / ±8g / ±16g selectable full scales. I2C/SPI interface output. 8-bit data output. 6D/4D orientation detection. Free fall detection, “sleep to walk” and “return to sleep” functions, motion detection etc.
NXP SemiconductorsPart number: MMA8452Q. 12-bit and 8-bit digital output. 1.95 to 3.6 V supply voltage. User selectable full scales of ±2g / ±4g / ±8g. I2C digital output interface. Current consumption: 6 µA to 165 µA.