How to Choose an IMU
Choosing an inertial measurement unit comes down to a handful of questions about what you need to measure, where the sensor will live and how it will talk to the rest of your system. This guide walks through them in order and ends with a table that maps the answers to LPMS models. If you are new to the terminology, start with What is an IMU?.
1. What do you actually need to measure?
- Orientation (roll, pitch, yaw) is what an AHRS delivers directly. Any 9-axis LPMS sensor does this.
- Heading only, for steering a vehicle or robot, puts all the weight on the Z-axis gyroscope. A unit with a dedicated low-noise heading gyroscope such as the LPMS-NAV3 outperforms a general 9-axis IMU here.
- Tilt on a slow-moving structure is an inclinometer problem. The LPMS-INC1 resolves 0.011° RMS without the complexity of a full IMU.
- Position needs an aiding source. Outdoors that is GNSS (LPMS-IG1P); on vehicles it is odometry fused with the IMU; indoors it is optical tracking or SLAM.
- Vibration and shock need a high, stable sample rate and a wide measurement range rather than the best orientation accuracy.
2. 6-axis or 9-axis?
The magnetometer in a 9-axis IMU is what makes yaw absolute (referenced to magnetic north) and drift-free. It is also the sensor most easily disturbed: mount a 9-axis unit next to a motor, a steel chassis or a power cable and the heading will be pulled. If the sensor sits in a magnetically noisy place and only relative heading is needed, a 6-axis unit with a good gyroscope, such as the LPMS-NAV3 or the LPMS-HR, is the more robust choice. LPMS 9-axis sensors can also be switched to a 6-axis fusion mode in software.
3. Which interface and protocol?
| Interface | Typical host | Notes |
|---|---|---|
| USB | PC, laptop, single-board computer | Simplest for evaluation and desktop tools. All wired LPMS units carry USB alongside their main interface. |
| CAN bus | Vehicles, industrial controllers, robots | Multi-drop, robust over long cables. LPMS CAN units support CANopen and a configurable sequential CAN format. |
| RS232 | PLCs, embedded boards, legacy equipment | Point-to-point up to 921,600 bps. LP-BUS binary or plain ASCII output. |
| RS485 / RS422 | Long runs and noisy plants | Differential signalling; the LPMS-NAV3 RS485 also speaks MODBUS. |
| TTL / UART | Microcontrollers | Direct 3.3 V logic level connection, no transceiver needed. |
| Bluetooth | Body-worn sensors, mobile devices | The LPMS-B2 runs Bluetooth Classic and BLE, up to 7 units per host. |
| Wi-Fi | Industrial IoT, remote machinery | The LPMS-IG1W streams over TCP/IP or MQTT with no internet connection required. |
Decide this early: interface variants are separate part numbers, and the connector and housing follow from it.
4. Where will the sensor live?
- Indoors on a bench or inside an enclosure: a plastic-housed LPMS-U3 or a bare LPMS-CURS3 board.
- Outdoors, wet or dusty: IP67 aluminium housings with M12 connectors, as on the LPMS-AL3, LPMS-IG1, LPMS-IG1P, LPMS-IG1W and LPMS-NAV3.
- Extreme temperature: check the operating range. Standard LPMS units cover -20 to +80 °C; the LPMS-HR and extended variants of the LPMS-NAV3 reach -40 °C.
- Vibration: aluminium housings and rigid mounting keep the sensor coupled to the structure; choose a range that will not clip.
5. How much accuracy and how little drift?
Look past the headline accuracy figure to the gyroscope noise density and bias stability, because those decide how the sensor behaves between corrections. The LPMS-IG1’s low-noise gyroscope (0.002 °/s/√Hz) gives it < 0.3° static and < 1° RMS dynamic accuracy, compared with < 0.5° and < 2° RMS on the standard 9-axis models. For heading, the 24-bit ±400 °/s gyroscope in the LPMS-NAV3 is the deciding component.
6. Data rate and latency
Control loops and motion capture want the freshest sample possible. LPMS sensors run their fusion at up to 500 Hz (1000 Hz on the LPMS-HR) and let you configure the output rate down to what your link and host can handle. Wireless links are the bottleneck: Bluetooth tops out at 400 Hz for a single LPMS-B2 and lower with several units; the LPMS-IG1W delivers 200 Hz over MQTT or 500 Hz over a raw socket.
7. Size, power and mounting
OEM integration favours the 22 × 28 mm LPMS-CURS3 at 4 g or the 2 g LPMS-B2 OEM module. Wearables need battery life: the LPMS-B2 runs more than six hours per charge. Most wired units accept 5-18 V DC; the LPMS-IG1 and LPMS-INC1 accept up to 36 V, so they can hang directly on a vehicle supply.
8. Software and integration
An IMU is only as useful as the path from its output into your software. LPMS sensors are configured with LPMS-Control2 on Windows, and integrated through OpenZen, our open-source C++ library with Python and C# bindings and ROS / ROS 2 drivers, or through FusionHub when the IMU is one of several sensors to be fused. Our IMU and ROS guide shows the typical setup.
Which LPMS model fits?
| Requirement | Recommended model |
|---|---|
| Body-worn, wireless, several sensors at once | LPMS-B2 |
| Compact wired sensor for robots, machines and research | LPMS-U3 |
| Board-level module for your own product | LPMS-CURS3 |
| Rugged 9-axis sensor on outdoor or industrial machinery | LPMS-AL3 |
| Highest orientation accuracy, vehicle dead reckoning | LPMS-IG1 |
| GNSS position and IMU orientation in one IP67 unit | LPMS-IG1P |
| Wireless sensor for industrial IoT and vibration monitoring | LPMS-IG1W |
| Stable heading for AGVs and mobile robots | LPMS-NAV3 |
| High-resolution 6-axis sensor for humanoid and legged robots | LPMS-HR |
| Precision tilt on cranes, booms, towers and bridges | LPMS-INC1 |
Evaluate before you commit
Datasheets rarely settle the choice. Order one unit of the closest model, mount it where the production sensor will go, log a representative run with LPMS-Control2 and look at the heading drift and noise in your own environment. All models are listed on the inertial measurement units page; for quotations, distributor contacts or a custom configuration, contact us.