Manuals+

WitMotion HWT901B

HWT901B Inclinometer User Manual

9-axis Accelerometer + Inclinometer with MPU9250, Digital Compass, and Air Pressure Sensor

1. Introduction

The WitMotion HWT901B is a high-performance Attitude and Heading Reference System (AHRS) designed for precise tilt angle measurement. It integrates a MEMS accelerometer, gyroscope, and a military-grade PNI RM3100 geomagnetic sensor, providing drift-free roll, pitch, and true North-referenced yaw data. The sensor utilizes an advanced R&D dynamic fusion algorithm and Kalman Filtering for accurate data output, excellent bias stability, and a low noise level. It is available in various interface options including TTL, RS232, RS485, and CAN.

HWT901B Inclinometer Overview
Figure 1: HWT901B Inclinometer highlighting key features like Gyro, Acceleration, Angle, Magnet Field, Air Pressure, and Kalman Filtering.

The HWT901B is equipped with a low-power 32-bit core processor, reaching up to 168MHz for faster data processing. It offers superior accuracy and stability, making it suitable for challenging environments. An IP67 waterproof version is also available for enhanced durability.

HWT901B Key Features
Figure 2: Key features including MEMS Sensor Chip, Magnetometer Chip, MCU Processor, IP67 Protection, and Robust Casing.

2. Package Contents

Upon receiving your HWT901B Inclinometer, please verify that all components are present and in good condition:

  • HWT901B Sensor Unit (Standard or IP67 version)
  • Connection Cable (1 meter for TTL, longer options available for other interfaces)
  • User Manual (PDF available online)
  • Product Catalog
Product Packaging and Contents
Figure 3: Typical HWT901B product packaging and included items.

3. Technical Specifications

The HWT901B series offers robust performance for various applications. Below are the detailed specifications:

AttributeValue
NameHWT901B
ChipsMEMS Accelerometer + Gyroscope + PNI RM3100
VoltageTTL/RS232/RS485: 5~36V, CAN: 5~24V
Current Consumption<40mA (Typical)
InterfaceTTL / RS232 / RS485 / CAN (optional)
Data Output3D (Acceleration, Gyro, Angle, Magnetic field), Quaternion, Time
Sensing RangeAcceleration: ±16g, Gyro: ±2000°/s
Measurement AngleX, Z-axis: ±180°, Y-axis: ±90°
Angle AccuracyX, Y axis static 0.05°, dynamic 0.1°, Z axis: 1° (after calibrated)
Magnetic Field1mg (milligauss)
Output Frequency0.1Hz to 200Hz (10Hz default, adjustable)
Baud Rate4800~921600bps
Product Size55mm x 36.8mm x 24mm
Cable Length1 meter (standard)
ProtocolRS485: ModBus RTU, RS232: Witmotion-Protocol
ChipBuilt-in military-grade high-precision RM3100 magnet module
IP RatingIP67 (for waterproof version)
HWT901B Technical Specifications Table
Figure 4: Detailed technical specifications for the HWT901B series.

4. Setup and Connection

Follow these steps to set up your HWT901B sensor:

4.1 Pin Definitions

Ensure correct wiring based on your chosen interface (TTL, RS232, RS485, CAN). Incorrect wiring can damage the device.

HWT901B Pin Definitions
Figure 5: HWT901B dimensions and pin definitions for TTL, RS232, RS485, CAN, and MCU connections.
  • TTL Pin Definition: RED (VCC 5V), YELLOW (TX), GREEN (RX), BLACK (GND).
  • RS232 Pin Definition: RED (VCC 5~36V), YELLOW (TX), GREEN (RX), BLACK (GND).
  • RS485 Pin Definition: RED (VCC 5~36V), YELLOW (A), GREEN (B), BLACK (GND).
  • CAN Pin Definition: RED (VCC 5~24V), YELLOW (CANH), GREEN (CANL), BLACK (GND).

4.2 Software Installation (PC)

To use the HWT901B with a PC, you will need to install the necessary drivers and software:

  1. Download the complete tutorial and related software (MiniIMU.exe) from the WitMotion document center. You can access it by scanning the QR code provided in Section 8.
  2. Unzip the downloaded file.
  3. Install the CH340 or CP2102 serial drivers.
  4. Connect the sensor to your PC using the correct PIN wiring and a USB-UART serial converter (not included).
  5. Open the MiniIMU.exe software.
  6. The software should auto-search and display data once connected.
PC Software Setup and Data Display
Figure 6: PC software interface demonstrating setup and real-time data display.

4.3 Android App Setup

The HWT901B supports serial connection with Android smartphones. An Android App is available for configuration and data viewing.

  1. Download the WitMotion Android App from the document center.
  2. Connect the sensor to your Android device using the appropriate USB adapter (e.g., USB Type-C/Micro USB to USB adapter, not included).
  3. Open the app to configure the sensor and view data.
Android App Interface
Figure 7: Android App interface for sensor configuration and data visualization.

5. Operation

5.1 Data Acquisition

Once connected, the sensor will output 3-axis acceleration, angular rate, angle, and magnetic field data. The standard version also outputs air pressure and height data. The output frequency is adjustable from 0.1Hz to 200Hz (10Hz default).

Easy to Read Graphs
Figure 8: Real-time graphical representation of sensor data in the PC software.

5.2 Configuration Menu

The PC software provides a comprehensive configuration menu to customize sensor parameters:

  • Calibration: Perform acceleration and magnetic field calibration.
  • Placement Direction: Adjust installation direction settings.
  • Output Frequency: Set the desired data output rate.
  • Bandwidth Setting: Configure sensor bandwidth.
  • Output Content: Select which data parameters (Time, Acceleration, Velocity, Angle, Magnetism, Pressure, Location, etc.) are outputted.
HWT901B Configuration Menu
Figure 9: Screenshot of the sensor configuration menu in the PC software.

5.3 Data Storage and Export

The software allows you to record raw data and extract analyzed data to TXT files, which can then be easily imported into Excel for further analysis.

Powerful Data Storage & Export
Figure 10: Data storage and export functionality within the PC software.

5.4 Temperature Drift Compensation

The HWT901B undergoes rigorous temperature drift testing and algorithmic compensation during manufacturing to ensure stable performance across its operating temperature range (-40°C to 80°C).

Video 1: Demonstration of temperature drift testing and algorithmic compensation for the HWT901B sensor.

6. Maintenance

  • Cleaning: Use a soft, dry cloth to clean the sensor's exterior. Avoid using harsh chemicals or abrasive materials.
  • Storage: Store the sensor in a dry, dust-free environment away from extreme temperatures and direct sunlight.
  • Cable Integrity: Regularly inspect the connection cable for any signs of wear or damage. Replace if necessary to ensure reliable data transmission.
  • Environmental Protection: If using the standard version, avoid exposure to water or high humidity. The IP67 waterproof version is designed for rugged environments but should still be handled with care to prevent physical damage.

7. Troubleshooting

  • No Data Output:
    • Check all cable connections to ensure they are secure and correctly wired according to the pin definitions.
    • Verify that the USB-UART serial converter (if used) is properly installed and recognized by your computer.
    • Ensure the correct COM port and baud rate are selected in the PC software or Android App.
    • Restart the software and reconnect the sensor.
  • Inaccurate Readings:
    • Perform a calibration of the acceleration and magnetic field sensors using the software's configuration menu.
    • Ensure the sensor is mounted securely and is not subject to excessive vibration or magnetic interference.
    • Check for any nearby strong magnetic fields that might affect the digital compass.
  • Software Not Recognizing Sensor:
    • Reinstall the CH340/CP2102 drivers.
    • Try a different USB port or a different USB-UART serial converter.
    • Ensure no other applications are using the same COM port.

If you encounter persistent issues, please contact WitMotion technical support at support@wit-motion.com. They typically respond within 12 hours.

8. User Tips

  • USB-UART Serial Converter: A USB-UART serial converter is required for connecting the sensor to a PC or mobile device. These are sold separately.
  • Arduino/Raspberry Pi Compatibility: For Arduino or Raspberry Pi projects, the HWT901B with a TTL interface is highly recommended due to common voltage levels. If using RS232/RS485 versions, a hardware converter to TTL will be necessary.
  • Standard vs. Waterproof Version: The standard HWT901B includes a barometer for air pressure and height data but is not waterproof. The HWT901B waterproof version (IP67 rated) does not include a barometer due to its glue-pouring manufacturing process.
  • iOS Incompatibility: WitMotion serial sensors, including the HWT901B, are not compatible with iOS operating systems. For iPhone compatibility, consider the WitMotion WT901BLECL model.
  • Customization Options: For orders of 20 units or more, customization options such as longer cables, OEM logo printing, and customized functions are available. Contact WitMotion directly for details.

9. Resources and Support

For detailed tutorials, datasheets, PC software, drivers, and sample code, please visit the WitMotion document center:

QR Code for WitMotion Document Center
Figure 11: Scan this QR code to access the WitMotion Document Center for comprehensive resources.

A PDF version of the user manual is also available for download: HWT901B User Manual (PDF)

9.1 Development Kits

WitMotion provides development kits including free software for Windows PC (MiniIMU.exe), CH340 & CP2102 serial drivers, and sample code for various platforms like STM32, Arduino, 51, Windows C++, Windows C#, and Matlab.

Development Kits and Resources
Figure 12: Overview of available development kits and resources.

9.2 Certifications

The HWT901B series holds various certifications, ensuring quality and compliance.

Product Certifications and Qualifications
Figure 13: Product certifications including Calibration Report, IP-rating, CE, and ISO:9001.

10. Warranty and Technical Support

WitMotion provides lifetime technical support for the HWT901B Inclinometer. If you have any questions or require assistance, please do not hesitate to contact their technical support team.