WITMOTION HWT905(RS232) IP67 Inclinometer User Manual
Tutorial Links and Support
Access valuable resources for the HWT905 inclinometer:
If you encounter technical issues or require assistance, WITMOTION's engineering team is committed to providing the necessary support for the successful operation of their AHRS sensors.
Contact Information
For technical support, please refer to the Technical Support Contact Info.
Applications
The HWT905 inclinometer is suitable for a wide range of applications, including:
- AGV Truck
- Platform Stability
- Auto Safety System
- 3D Virtual Reality
- Industrial Control
- Robot
- Car Navigation
- UAV
- Truck-mounted Satellite Antenna Equipment
1 Introduction
The HWT905 is a multi-sensor device capable of detecting acceleration, angular velocity, angle, and magnetic field. Its robust housing and compact design make it ideal for industrial applications such as condition monitoring and predictive maintenance. By interpreting sensor data through smart algorithms, the device supports a broad variety of use cases.
The HWT905 is scientifically known as an AHRS IMU sensor. It measures 3-axis angle, angular velocity, acceleration, and magnetic field, with its primary strength lying in its algorithm for accurate three-axis angle calculation.
Key advantages of the HWT905 over competing sensors include:
- Heated for best data availability: Features a new WITMOTION patented zero-bias automatic detection calibration algorithm that outperforms traditional accelerometer sensors.
- High precision output: Provides Roll, Pitch, Yaw (X, Y, Z axis) Acceleration, Angular Velocity, Angle, and Magnetic Field data.
- Low cost of ownership: Offers remote diagnostics and lifetime technical support from the WITMOTION service team.
- Comprehensive development resources: Includes tutorials, datasheets, demo videos, free software for Windows, an Android app, and sample code for MCU integration (51 serial, STM32, Arduino, Matlab, Raspberry Pi), along with communication protocols.
- Industry recognition: WITMOTION sensors are praised by thousands of engineers as a recommended attitude measurement solution.
1.1 Warning Statement
Please observe the following safety precautions:
- Applying more than 36 Volts across the sensor's power supply wiring can cause permanent damage.
- Never connect VCC directly to GND, as this can burn out the circuit board.
- For proper instrument grounding, use WITMOTION's original factory-made cables or accessories.
- Do not attempt to access the I2C interface.
- For secondary development projects or integration, use WITMOTION's compiled sample code.
2 Use Instructions with PC
2.1 Connection Method
The PC software is compatible only with Windows systems. For a demonstration, refer to the HWT905's demo video.
2.1.1 Serial Connection
Step 1. Connect the sensor with a serial converter.
PIN Connections:
- VCC: 9~36V
- TX: Yellow
- RX: Green
- GND: GND
(When connecting to a computer, VCC of 9~36V is recommended.)
Diagram Description: A diagram illustrates the RS232 PIN DEFINITION with color-coded connections (RED for VCC 5V, YELLOW for TX, GREEN for RX, BLACK for GND). A sensor connection diagram shows pins labeled VCC, TX, RX, GND from the sensor connecting to a serial converter, which then connects to a power source (9~36V) and the computer.
2.1.2 Recommended Tools and Software Setup
Recommended tools:
- Tutorial for 3-in-1 serial converter (CH340 driver)
- Tutorial for 6-in-1 serial converter (CP2102 driver)
Step 1. Unzip and install the appropriate driver (CH340 or CP2102) for your accessory.
Diagram Description: A screenshot of the Windows Device Manager is shown, highlighting 'Silicon Labs CP210x USB to UART Bridge (COM15)' listed under Ports (COM & LPT).
Step 2. Insert the converter into your computer and confirm the "com port" in Device Manager.
Step 3. Open the software (Minimu.exe). Data will appear after auto-search finishes.
Notice: If the connection is unsuccessful, please operate manually. Select the correct COM port and set the baud rate to 9600; data should then be displayed in the software.
2.2 Software Introduction
Download the latest version of the software from the link to download software.
2.2.1 Main Menu
Diagram Description: A screenshot of the WITMOTION software interface displays the 'Attitude Measurement System' with Angle X, Y, and Z values shown prominently. The menu bar includes File, Tools, Record, 3D, Config, Help, and Auto-search. Below the main display, buttons for 'Acc Calibrate' and 'Alarm Set' are visible. A table details the main menu options and their functions.
| Button | Function |
|---|---|
| File | Launch recorded HEX file (Bin format) |
| Tools | Hide or display tools box on left side |
| Record | Record function |
| 3D | 3D DEMO |
| Config | Configuration setting |
| Language | English or Chinese |
| Help | Binding device or unbind |
| Bluetooth Set | Firmware update |
| Firmware update | Option for firmware update |
| About Minimu | Info about Minimu.exe |
| Factory test | For manufacturer internal test only |
| Auto-search | Auto searching the sensor |
| Port | Com port selection |
| Button | Function |
|---|---|
| Baud | Baud rate selection |
| Type | Fixed setting as Normal for HWT905 |
| Open | Open com port |
| Close | Close com port |
2.2.2 Menu of Configuration
Diagram Description: A screenshot of the WITMOTION software's configuration interface is shown, featuring sections for System, Calibrate, Range, Communication, Content, and Port. Various settings and options are displayed, including algorithm selection, installation direction, and data output choices.
| Button | Function |
|---|---|
| Read Config | Reading the current configuration |
| Lock | Lock the sensor |
| Unlock | Unlock the sensor |
| Calibrate Time | Calibration time of chip |
| Save Config | Save configuration |
| Button | Function |
|---|---|
| Reset | Reset to factory setting |
| Sleep | Sleep function |
| Alarm | Alarm function |
| Algorithm | 6-axis algorithm or 9-axis |
| Installation Direction | Vertical or horizontal installation |
| Instruction Start-up | Instructions sending to start-up the sensor |
| Button | Function |
|---|---|
| Acceleration | Accelerometer calibration |
| Magnetic Field | Magnetometer calibration |
| Reset Height | Reset height data to 0 (only for sensor built-in barometer, including WT901B, WTGAHRS2, WTGAHRS1, HWT901B) |
| Reset Z-axis Angle | Reset Z-axis angle to 0 degree, not available for HWT905 in 9-axis algorithm |
| Angle Reference | Setting current angle as 0 degree |
| Gyro Auto Calibrate | Auto-calibration of gyroscope |
| Button | Function |
|---|---|
| Acceleration | Acceleration measurement range |
| Gyro | Gyroscope measurement range |
| Band Width | Bandwidth range |
| GPS Time Zone | GPS positioning of time zone |
| Button | Function |
|---|---|
| Baud Rate | Baud rate selection |
| Output Rate | Return rate selection |
| Device Address | Interface for R&D |
| Button | Function |
|---|---|
| Time | Time data output |
| Acceleration | Acceleration data output |
| Velocity | Angular velocity data output |
| Angle | Angle data output |
| Magnetism | Magnetic field data output |
| Port | Port data output |
| Pressure | Pressure output, only available with the sensor built-in barometer like HWT901B, WTGAHRS1, WTGAHRS2, WT901B, etc |
| Location | Latitude&Longitude data output, only for GPS IMU series, such as WTGAHRS1, WTGAHRS2 |
| PDOP | Ground velocity data output, only for GPS IMU series, such as WTGAHRS1, WTGAHRS2 |
| Quaternion | Quaternion data output |
| Positioning Accuracy | Option for GPS positioning accuracy output, including Satellite quantity, PDOP, HDOP, VDOP data, only for GPS IMU series, such as WTGAHRS1, WTGAHRS2 |
| GPS Original | Only output GPS raw data, only for GPS IMU series, such as WTGAHRS1, WTGAHRS2 |
| Button | Function |
|---|---|
| D0 Model | Extended port D0 |
| D1 Model | Extended port D1 |
| D2 Model | Extended port D2 |
| D3 Model | Extended port D3 |
| Pulse width | Pulse width of PWM |
| Cycle | Cycle of PWM |
2.3 Calibration
Preparation: Ensure the sensor is set to "Online" mode.
Calibration on PC software: Calibration is required for the first-time usage of the device.
2.3.1 Accelerometer Calibration
Purpose: This calibration removes the zero bias of the accelerometer. Without calibration, there may be varying degrees of bias error; after calibration, measurements become accurate.
Methods:
- Keep the module horizontally stationary.
- Click the "Accelerometer calibration" button.
- Click "Start calibration" and wait for 3 seconds.
Diagram Description: A screenshot of the 'AccCal' window for accelerometer calibration is displayed. It shows input fields for X, Y, and Z values, along with operating instructions: place the module face up, click 'Start calibration' for automatic calculation, wait for data stability, then click 'Finish calibration'. Buttons for 'Read parameter', 'Start calibration', and 'Write parameter' are present.
- Click "Complete Calibration".
Step 5. Judge the result: Confirm if there is 1g on the Z-axis acceleration.
Observation: After 1-2 seconds, the three axial acceleration values should be approximately 0, 0, and 1. The X and Y axis angles should be around 0°. After calibration, the x-y axis angle accuracy improves.
Note: When the module is placed horizontally, there should be 1g of gravitational acceleration on the Z-axis.
2.3.2 Magnetic Field Calibration
Purpose: Magnetic calibration removes the zero bias of the magnetic field sensor, which often has a significant error upon manufacturing. Uncalibrated sensors can lead to large measurement errors, affecting the accuracy of the z-axis angle and heading angle.
Preparation: Ensure the sensor is at least 20 cm away from magnetic and iron materials.
Methods:
- Open the "Config" menu.
- Click the "Magnetic Field" calibration button and then click "Start calibration".
Diagram Description: Screenshots show the 'MagCal' window with three charts (chartXZ, chartYZ, chartXY) plotting data points during calibration. The calibration method is set to 'Ellipse fitting'. Parameters like Current Value, Offset, and Range for X, Y, Z axes are displayed. Buttons for 'View operating instructions', 'Start Calibrate', 'Read Parameters', and 'Write Parameters' are available.
- Slowly rotate the module 360° around the X, Y, and Z axes.
Step 4. After rotation, click "End calibration".
Successful result: Most data points should fall within the ellipse. If unsuccessful, move the sensor away from sources of magnetic interference.
2.3.3 Gyroscope Automatic Calibration
The gyroscope calibration process calibrates the angular velocity, and the sensor performs this automatically. It is recommended to deactivate automatic gyroscope calibration only if the module is rotating at a constant speed.
2.3.4 Reset Z-axis Angle
Note: To mitigate magnetic interference, you can switch to the 6-axis algorithm, which allows for resetting the Z-axis angle. The z-axis angle is an absolute angle, referencing the northeast sky as the coordinate system, and cannot be relative to 0 degrees by default.
Setting the Z-axis to 0 makes the initial angle relative to 0 degrees. If the z-axis drifts significantly during use, it can be recalibrated. When powered on, the Z-axis will automatically return to 0.
Calibration Method: Keep the module static, navigate to the "Config" menu, open the configuration bar, and select "Reset Z-axis Angle". The Z-axis angle should then display as 0 degrees in the module's data bar.
2.3.5 Reset Height to 0
This function is only available for modules equipped with a built-in barometer (e.g., WT901B, HWT901B, WTGAHRS1, WTGAHRS2).
2.4 Configuration
2.4.1 Return Content
Setting Method: The content of the data returned by the module can be customized based on user needs. Click the configuration option bar and select the desired data content to be output.
For the HWT905, the default output includes acceleration, angular velocity, angle, and magnetic field.
Notice: If "GPS Original" is selected, no other data will be output.
2.4.2 Output Rate
The default return rate of the module is 10Hz, with a maximum supported rate of 200Hz. A 10Hz rate signifies 10 data packets returned per second, with each packet being 33 bytes by default.
Note: If a large amount of data is being transmitted and the communication baud rate is low, data transmission may be compromised. In such cases, the module will automatically reduce the frequency to the maximum allowable output rate. Therefore, a higher return rate generally requires a higher baud rate, typically 115200.
2.4.3 Baud Rate
The module supports multiple baud rates, with 9600 being the default. To set the baud rate, select the desired rate from the communication rate drop-down box in the configuration bar, ensuring it matches the connection between the software and the module.
Note: After changing the baud rate, the module will no longer output data at the original rate. Data will only be output when the newly set baud rate is selected in the PC software.
2.4.4 Data Recording
Method:
- Click "Record" and then "Begin".
- Click "Stop" to end recording.
Diagram Description: A screenshot of the WITMOTION software shows the 'Record' function active, with a 'Begin' button and a 'Stop' button available. Real-time data is being displayed.
2.4.5 Data Playback
New Function: Each time a recording is created, a BIN file is generated in the installed software's record file folder. This allows for recorded data playback.
Recorded data playback method:
- Disconnect the sensor.
- Click the "File" button, then select "Load".
- Choose the BIN file from the software's installation path (typically within a 'recordFile' folder).
- Click "Run". The binary file will then be played back, and the playback rate can be edited.
Diagram Description: Screenshots illustrate the data playback process. The first shows the 'ReadFile' window with options to load a file. The second shows a file explorer window navigated to the 'recordFile' directory, listing various .BIN files. The third shows the playback interface with Angle X, Y, Z values and a playback rate control.
2.4.6 Standby and Wake Up
Sleep: The module pauses its operation and enters standby mode, reducing power consumption.
Wake Up: The module returns to its working state from standby mode.
The module defaults to a working state. To enter sleep mode, navigate to "Config" in the software and click "Sleep". Click "Sleep" again to release the module from sleep.
Diagram Description: A screenshot of the WITMOTION software configuration menu highlights the "Sleep" button under the "System" section.
2.4.7 Placement Direction
The default installation direction for the module is horizontal. The vertical installation direction can be set if needed.
- Rotate the module 90 degrees around the X-axis.
- Place the sensor vertically.
- In the "Config" menu, click "Vertical" under the "Install Direction" setting.
Diagram Description: A screenshot of the WITMOTION software configuration menu shows the "Install Direction" dropdown set to "Vertical".
2.4.8 Bandwidth
The default bandwidth is 20Hz.
Function:
- A higher bandwidth setting leads to greater fluctuation in the data waveform. Conversely, a lower bandwidth results in a more fluent data stream. For example, a bandwidth of 20Hz with an output rate of 10Hz produces a very steady waveform.
Diagram Description: Two sets of screenshots show the software interface and corresponding waveform plots. The first set displays a steady waveform with a 20Hz bandwidth. The second set shows a more fluctuating waveform with a 256Hz bandwidth.
- Increasing the bandwidth helps resolve data-repeating issues. For instance, with a bandwidth of 20Hz and a retrieval rate of 100Hz, data may repeat 5 times. To ensure no repeating data, the bandwidth should be set higher than 100Hz.
2.4.9 Restore Factory Setting
Operation Method: Connect the HWT905 to your computer via a USB-to-serial port module. Navigate to the configuration option, open the configuration bar, and click "Reset". After restoring factory settings, power the module on again. (Note: This method requires knowing the module's baud rate in advance; if it does not match, the instruction will not take effect.)
2.4.10 6-axis/ 9-axis Algorithm
6-axis algorithm: The Z-axis angle is primarily calculated based on angular velocity integration, which may introduce calculated errors on the Z-axis angle.
9-axis algorithm: The Z-axis angle is calculated and analyzed based on the magnetic field. This algorithm may exhibit slight drift in the Z-axis angle.
The HWT905 defaults to the 9-axis algorithm. If the installation environment has significant magnetic field interference, it is recommended to switch to the 6-axis algorithm for angle detection.
Method:
- Switch to the "6-axis" algorithm via the "Config" menu.
- Perform "Accelerometer calibration" and "Reset Z-axis angle" calibration.
After calibration is complete, the device can be used normally.
Diagram Description: A screenshot of the WITMOTION software configuration menu shows the "Algorithm" dropdown with options for "9-axis" and "6-axis" selected.
3 MCU Connection
Diagram Description: A diagram illustrates the MCU connection, showing the sensor's VCC, 232TX, 232RX, and GND pins connecting to corresponding pins on an MCU module.
Access sample code and instructions:
Notice: Currently, no sample code is provided for Linux or Python systems.
