General support information

Protocol Max Speed Typical Max Cable Length Key Considerations CAN 1 Mbps 40 m Needs termination (120Ω) RS-232 115.2 kbps 5-15 m Single-ended, noise-sensitive RS-422 10 Mbps 12 m (120 m @ 1 Mbps) Differential, multi-drop USB 2.0 480 Mbps 5 m (passive) Requires hubs for longer runs USB 3.0 5 Gbps 3 m (passive) Active optical for > 3 m General Recommendations For long distances (industrial/automotive): Use CAN or RS-422. For short-distance PC peripherals: USB (with extenders if needed). Legacy systems: RS-232 is limited; prefer RS-422 for better range. Signal Integrity: Always use shielded twisted-pair (STP) cables in noisy environments.

NMEA stands for National Marine Electronics Association which has devised numerous data telegrams to allow vessel electronic equipment to communicate with each other. The NMEA 0183 Interface Standard defines electrical signal requirements, data transmission protocol and time, and specific sentence formats for a 4800-baud serial data bus. Each bus may have only one talker but many listeners. This standard is intended to support one-way serial data transmission from a single talker to one or more listeners. This data is in printable ASCII form and may include information such as position, speed, and depth.More information is available from the NMEA website.

Tactical grade MEMS gyroscopes (zero bias <1 °/hr) can achieve ± 0.5 °~1 ° north-seeking accuracy in static environments through multi position calibration (such as the 24-point method) and Kalman filtering, making them suitable for low-cost vehicle mounted/portable devices. However, in dynamic environments, the accuracy drops sharply, and long-term work requires auxiliary sensors (such as GNSS timing and Earth angular velocity synchronization).

Flux gate sensors are used to detect weak magnetic fields, such as in geomagnetic navigation and scientific instruments. When it comes to application scenarios that require low cost, low power consumption, and high frequency response (such as motor control and consumer electronics), choose Hall effect sensors.

In the signal acquisition of quartz flexible acceleration sensors, the current frequency conversion module based on charge integration performs well in anti-interference, dynamic range, resolution, and power consumption, especially suitable for weak signals, high noise environments, and low-power demand scenarios. Traditional AD conversion modules are more suitable for systems that require fixed sampling rates, multi-channel synchronization, or complex digital processing. When making a choice, it is necessary to weigh the characteristics of both based on the specific application.

In scenarios that require high-precision inertial navigation, high-performance MEMS inertial sensors have been able to partially replace fiber optic gyroscopes (FOGs) in recent years, but whether it can be completely replaced depends on specific application requirements. For example, the MEMS IMU U6488 produced by Micro-Magic Inc., the bias instability of the gyroscope can reach 0.2°/h, and the accuracy of Zero bias stability (1 σ, 10s) can reach 1°/h; Random walk reaches 0.03 º/√hr; This product can replace low precision fiber optic gyroscopes to meet short-term high dynamic tasks (less than 30 minutes), or in GNSS assisted scenarios, the position error of combined navigation (such as RTK + high-precision MEMS) can be less than 1 meter.

Compared with GNSS/INS integrated navigation systems, pure inertial navigation (relying only on inertial sensors and not on external signals such as GNSS) has unique advantages in specific scenarios, mainly reflected in autonomy, reliability, environmental adaptability, and system simplification; Fully autonomous operation, independent of external signals: High dynamic performance and real-time capability, GNSS update rate is usually 1-10Hz, which cannot meet the real-time control requirements of high dynamic carriers (such as fighter jets and missiles). At the same time, GNSS has signal transmission and resolution delays (about 100ms). The data update rate of inertial navigation is extremely high (100Hz~1kHz), and the output is almost delay free, suitable for high-speed obstacle avoidance and stable platform control. Pure inertial navigation has strong environmental adaptability and is not affected by weather conditions such as thunderstorms and sandstorms. The core weakness of pure inertial navigation is the accumulation of errors over time, but it can be optimized by selecting high-precision sensors such as fiber optic gyroscopes (FOG) and laser gyroscopes (RLG) with drift rates much lower than MEMS, which are suitable for long endurance tasks; Zero Velocity Update (ZUPT) technology and the method of regularly resetting the position.

The following shows the changes in the scale factor at different temperatures in our test report, and their variations are minimal at different temperatures. Please use the values at 25 ° C room temperature: 15143697

The gyroscope output data includes angular velocity and temperature data. The original value of angular velocity data is a 32-bit signed integer, and the temperature data is a 16-bit signed integer. Convert temperature data to Celsius temperature values: Assuming the received temperature data is Dt, Te=Dt * 0.0625, Te unit is ℃ Convert angular velocity data to angular velocity values in degrees per second: Assuming the received angular velocity data is Dg, the gyroscope scale factor given in the manual is Kg, and the sampling frequency (gyroscope communication frequency) is fs Angular velocity W=Dg/(Kg/fs)

Our fiber optic gyroscope supports RS422 bidirectional serial communication protocol. The transmitter (Tx+, Tx -) is used to send gyroscope measurement data to the client-side, and the receiver (Rx+, Rx -) is used to receive external trigger signals. You need to design a hardware circuit board as shown in the following design diagram, or use existing circuit design to utilize the following functions.

At present, our initial alignment uses two sensors, an accelerometer and a magnetometer, to calculate the current attitude angle (roll, pitch, yaw) as the initial alignment angle. When the user sends the instruction FF 5A 68 00 00 F0 1C 0D, the product automatically performs the above initial calibration work and continues to sense the attitude of the target carrier. At this point, AHRS returns the instruction FF 5A 68 00 01 00 1D D4 0D, only notifying the customer whether the initial calibration work was successfully performed. Please note that even if the above command is executed, the output is not zero due to sensor measurement errors.

Usually, we fix the MEMS IMU to the turntable, and the accelerometer collects data using a 12-position stationary method. The gyroscope collects data by rotating forward and backward at specific speeds (such as 30 °/s, 60 °/s, etc.), and uses optimization algorithms to obtain the zero bias, scaling factor, and misalignment error matrix of the accelerometer and gyroscope.