MSN300H High Dynamic MEMS North Finder

 

 

 

• Orientation in complex environments such as mines
• Petroleum inclination and north finding
• Pipeline surveying

 

 

MSN300H MEMS inertial North Finder adopts a strapdown north-finding scheme with built-in MEMS gyroscopes and MEMS accelerometers. The product can continuously track and measure changes in well deviation angle, tool face, and azimuth angle, and possesses continuous rotation attitude measurement capability.

MSN300H inertial North Finder integrates high-performance MEMS gyroscopes and MEMS accelerometers in a standalone structure. The product incorporates vibration-damping design to ensure accurate measurement of the carrier's angular and linear motion parameters even in harsh environments, providing users with a low-cost and highly reliable solution.

 

 

MEMS Gyroscope
Range (°/s)	±500
Bias @ Full temp. (°/h,3σ)	≤1.5
Bias Stability (°/h,10ssmoothing)	≤0.5
Bias Instability (°/h,allan,typ)	≤0.1
Bias Repeatability (°/h)	≤0.15
Angular Random Walk (°/√h)	≤0.03
Scale Factor Nonlinearity (ppm)	≤100
Cross-Coupling (rad)	≤0.001
Bandwidth (Hz)	≥50
MEMS Accelerometer
Range (g)	±16
Bias @ Full temp. (mg,3σ)	≤3
Bias Stability (μg,10ssmoothing)	≤100
Bias Instability (μg,allan,typ)	≤50
Bias Repeatability (ug)	≤100
Velocity Random Walk (m/s/√h)	≤0.04
Scale Factor Nonlinearity (ppm,±1g)	≤300
Cross-Coupling (rad)	≤0.001
Bandwidth (Hz)	≥50
Navigation accuracy
North Finding Accuracy (°,1σ)	≤2.5*secL(L for latitude)
Attitude Accuracy (°,1σ)	≤0.2
Physical Characteristics
Power Supply (V)	5~12(Ripple≤100mV)
Steady-state power(W)	≤2
Startup Time (s)	≤2
Communication interface	422
Update Rate (Hz,max)	200
Dimensions (mm×mm)	Φ31.8 × 85
Weight (g)	145±10g
Operating Environment
Operating Temp. (℃)	-40～+120
Storage Temp. (℃)	-55～+85
Vibration (g,RMS)	6.06,20~2000Hz
Shock (g)	500g/1ms

 

 

Product Overview

Key Features

• High performance and high cost-effectiveness
• -40℃ to +120℃ full temperature calibration and compensation
• Continuous roll measurement
• Domestically produced inertial components, independently controlled
• Strong harsh mechanical environment resistance
• Online firmware update capability
• Auto zero velocity correction
• North finding time configuration
• Installation misalignment angle correction

 

Applications

• Orientation in Complex Environments Such as Mines
• Petroleum Inclination and North Finding
• Pipeline Surveying

 

 

Table 1 MSN300H North Finder Performance Specifications

Gyroscope
Range (°/s)	±500
Bias @Full temp. (°/h,3σ)	≤1.5
Bias Stability (°/h,10sSmoothing)	≤0.5
Bias Instability (°/h,allan,typ)	≤0.1
Bias Repeatability (°/h)	≤0.15
Angle Random Walk (°/√h)	≤0.03
Scale Factor Nonlinearity (ppm)	≤100
Cross-Axis Coupling (rad)	≤0.001
Bandwidth (Hz)	≥50
Accelerometer
Range (g)	±16
Bias @Full temp. (mg, 3σ)	≤3
Bias Stability (μg, 10s Smoothing)	≤100
Bias Instability (μg, Allan Variance, typ)	≤50
Bias Repeatability (μg)	≤100
Velocity Random Walk (m/s/√h)	≤0.04
Scale Factor Nonlinearity (ppm, ±1g)	≤300
Cross-Axis Coupling (rad)	≤0.001
Bandwidth (Hz)	≥50
Navigation Accuracy
Auto North Finding Accuracy (°, 1σ)	≤2.5*secL(L represents the local latitude)
Attitude Accuracy (°, 1σ)	≤0.2
Physical Characteristics
Power Supply (V)	5~12(Ripple ≤ 100mV)
Steady-State Power Consumption (W)	≤2
Startup Time (s)	≤2
Communication Interface	422
Update Rate (Hz, max)	200
Dimensions (mm × mm × mm)	Φ31.8 × 85
Weight (g)	145±10g
Operating Environment
Operating Temperature (℃)	-40～+120
Storage Temperature (℃)	-55～+85
Vibration (g, RMS)	20~2000HZ,6.06
Shock (g)	500g/1ms

 

Mechanical Characteristics

The MSN300H North Finder system adopts an aerospace aluminum alloy structure with lightweight and high structural integrity, resistant to vibration and shock. The product is mounted with 6 M3 screws, with mechanical dimensions of Φ31.8 mm × 85 mm and a weight of 150 g, as shown in Fig. 1.

Fig. 1 Mechanical Dimensions

 

Product Marking and Orientation

The coordinate system definition of the High-Precision MEMS North Finder is shown in the figure. The product is placed horizontally with the marking arrow pointing upward. In the body frame: the X-axis points to the forward direction, the Y-axis points to the upward direction, and the Z-axis points to the right direction, i.e., the "Forward, Up, Right" coordinate system, corresponding to the "North, Up, East" navigation frame.

Fig.2 North Finder Body Frame Coordinate System and Navigation Frame Axis Definition

Heading Angle: The angle between the projection line of the vehicle's longitudinal axis (X-axis in the figure) on the local horizontal plane and the local geographic north direction. Positive is north to east, with a range of 0° to 360°, as shown in the figure below:

Fig.3 Heading Angle Measurement Definition (Top View)

Pitch Angle: The angle between the vehicle's longitudinal axis (X-axis in the figure) and its horizontal projection line. Positive when the vehicle pitches up, with a range of -90° to 90°, as shown in the figure below:

Fig.4 Pitch Angle Measurement Definition (Side View)

Roll Angle: The angle between the vehicle's lateral axis (Z-axis in the figure) and the horizon line. Positive when the vehicle rolls to the right, with a range of -180° to 180°, as shown in the figure below:

Fig.5 Roll Angle Measurement Definition (Rear View)

Virtual Heading Angle(Gyro Tool Face Angle): When the product operates in an inverted position (i.e., pitch angle is -90°), the roll angle and heading angle become singular angles and cannot accurately represent the vehicle's attitude. Therefore, a virtual heading angle is defined as the angle measured clockwise from the true north direction line to the Y-axis, with a range of 0 to 360°, as shown in the figure below.

Fig.6 Virtual Heading Angle(Top View)

 

In petroleum and coal industry north finding applications, the angle definitions are as follows:

Inclination Angle: The angle between the borehole direction line and the gravity line at the measurement point, with a range of 0 to 180°, and an initial inclination angle of 0°.

Azimuth Angle: The angle measured clockwise from the true north heading, with one full rotation covering 0 to 360°. This is equivalent to the heading angle.

Gravity Tool Face Angle: The angle of the tool face after the deflection tool reaches the bottom of the well. The range is 0 to 360°.

Gyro Tool Face Angle: The angle measured clockwise from the true north direction line to the horizontal projection of the intersection line between the tool face and the bottom-of-hole circular plane. The range is 0 to 360°, as shown in the figure below.

Fig. 7 Gyro Tool Face Angle(Top View)

 

During product operation, when the pitch angle is near 90°, the roll angle and heading angle have singularity problems. In general engineering applications, two different angle combinations are used based on the pitch angle output, with the following switching rules:

When the vehicle pitch angle is between -85° and +85°, use heading angle, pitch angle, and roll angle.

When the vehicle pitch angle is between -85° and -90° or between +85° and +90°, use pitch angle and virtual heading angle.

The quaternion represents the rotation between the North-Up-East navigation frame and the Forward-Up-Right body frame. The relationship between the quaternion and the attitude matrix is as follows:

Note: b denotes the Forward-Up-Right body frame; n denotes the North-Up-East navigation frame.

 

Interface Definition

The MSN300H High-Precision MEMS North Finder outputs via colored high-temperature cables, mainly for powering the north finder system and external communication. The connector pin definitions are shown in Table2:

Table2 MSN300H High-Precision MEMS North Finder Connector Pin Definitions

Wire Color	Cable Definition	Function Description	Remarks
Red	+5V	5V Power Supply	System Power Supply (5V~12v)
Black	GND	Power Ground
Purple	DB9_RS_422 T+	Data Transmit+	North Finder Data Transmit / Firmware Upgrade Configuration
Orange	DB9_RS_422 T-	Data Transmit−
Yellow	DB9_RS_422 R+	Data Receive+
Green	DB9_RS_422 R-	Data Receive−

After the power supply voltage drops below the device operating threshold voltage, the power-off hold time before powering on again t_OFF shall not be less than 3s; insufficient power-off interval may cause abnormal device startup, latch-up, or initialization failure.

 

Communication Protocol

Protocol 1:XDNSO-55AAProtocol

The MSN300H High-Precision MEMS Petroleum North Finder protocol defaults to periodic broadcast output at a frequency of 200 Hz, with 96 bytes per data frame, baud rate of 460800 bps, 1 start bit, 8 data bits, 1 stop bit, and no parity. For multi-byte variables, the low byte is transmitted first followed by the high byte (Little-Endian Format). The typical communication protocol is shown in Table 3. Under the petroleum north finder protocol, the output angles are in the vertical launch frame. Please note the attitude and heading output ranges.

Table3 MSN300H High-Precision MEMS Petroleum North Finder Communication Protocol

No.	Byte Start	Bytes	Content	Equivalent	Range	Unit	Remarks
1	0	1	0x55	1			Frame Header
2	1	1	0xAA	1			Frame Header
3	2	1	92	1			Data Length
4	3	4	PC num	1		5ms	5ms Counter Value
5	7	1	System Operating Status	-	-	-	16 (0x10): Self-Test In Progress; 18 (0x12): Self-Test Passed; 31 (0x1F): Self-Test Error; 51 (0x33): Coarse Alignment; 53 (0x35): Fine Alignment 65 (0x41): Navigating 67 (0x43): Zero Velocity Correction
6	8	1	Output Channel Status Word	-	-	-	0: Swinging North Finding Channel 1: Pure Static North Finding Channel
7	9	1	Over-Range Status	-	-	-	After the product enters alignment, within one navigation cycle of 5ms: bit0: X gyroscope over-range set to 1; bit1: Y gyroscope over-range set to 1; bit2: Z gyroscope over-range set to 1; Bit3: X accelerometer over-range set to 1; Bit4: Y accelerometer over-range set to 1; Bit5: Z accelerometer over-range set to 1; After re-alignment, the above statuses are cleared to 0.
8	10	1	Command Response Status				0x10: Correct command response successful, transmitted 5 packets consecutively. 0x1F: Command error, transmitted 5 packets consecutively to remind the user to check command configuration (output data or command out of range); original process unchanged. Note: After receiving a valid command, 5 packets of 0x10 status are fed back and a soft reset is performed. After receiving an invalid command, 5 packets of 0x1F status are fed back and the original state is maintained.
9	11	2	Total North Finding Time	1	-	s
10	13	2	Remaining North Finding Time	1		s
11	15	4	Angular Rate X	0.0000005		°/s	Average value within the output period (Forward)
12	19	4	Angular Rate Y	0.0000005		°/s	Average value within the output period (Upward)
13	23	4	Angular Rate Z	0.0000005		°/s	Average value within the output period (Rightward)
14	27	4	Acceleration X	0.000001		m/s2	Average value within the output period (Forward)
15	31	4	Acceleration Y	0.000001		m/s2	Average value within the output period (Upward)
16	35	4	Acceleration Z	0.000001		m/s2	Average value within the output period (Rightward)
17	39	4	Integrated Longitude	0.0000001		°	Instantaneous value at output time (Int)
18	43	4	Integrated Latitude	0.0000001		°	Instantaneous value at output time (Int)
19	47	2	Integrated Altitude	0.5		m	Instantaneous value at output time (Short)
20	49	2	Integrated North Velocity	0.04		m/s	Instantaneous value at output time
21	51	2	Integrated Up Velocity	0.04		m/s	Instantaneous value at output time
22	53	2	Integrated East Velocity	0.04		m/s	Instantaneous value at output time
23	55	2	Gravity Tool Face Angle	0.006	[0,360]	°	Instantaneous value at output timeUint16
24	57	2	Azimuth Angle	0.006	[0,360]	°	Positive is North to East Instantaneous value at output timeUint16
25	59	2	Inclination Angle	0.006	[0,180]	°	Instantaneous value at output timeUint16
26	61	1	Gyroscope Temperature	1		℃	Instantaneous value at output time
27	62	1	Accelerometer Temperature	1		℃	Instantaneous value at output time
28	63	4	Quaternion q0				In the North-Up-East coordinate system. IEEE 32-bit Float, Little-Endian.
29	67	4	Quaternion q1				Same as above
30	71	4	Quaternion q2	-		-	Same as above
31	75	4	Quaternion q3			-	Same as above
32	79	6	IMU Over-Range Counter	1		1	Incremented by 1 for each over-range occurrence within a 5ms navigation cycle. After reaching 255, counting restarts. If re-alignment is performed, counting resets. Little-Endian format, in the order of Gx, Gy, Gz, Ax, Ay, Az, each axis is Uint8.
33	85	1	Reserved			1	UInt8
34	86	1	Heading Correction Count			1	UInt8
35	87	2	Gravity Vector Sum	0.006		m/s2	Little-Endian FormatUint16
36	89	2	Gyro Tool Face Angle	0.006	[0,360]	°	Little-Endian FormatUint16
37	91	2	Horizontal Component of Earth Rotation Rate	0.006		°/h	Little-Endian FormatUint16
38	93	1	Vertical Mode Flag	1			UInt8, 0: Horizontal Mode; 1: Vertical Launch Mode;
39	94	1	Output Protocol Format	1			0xFF: General Petroleum North Finder Protocol
40	95	1	Checksum	1			Lower 8 bits of the cumulative sum of bytes at indices (2 to 94)

 

Protocol 2: Host Computer to North Finder Command Protocol

The MSN300H High-Precision MEMS North Finder can respond to commands in real time. The host computer sends trigger commands to the north finder system according to the following protocol: baud rate 460800 bps, 1 start bit, 8 data bits, 1 stop bit, no parity. For multi-byte variables, the low byte is transmitted first followed by the high byte (Little-Endian Format). The communication protocol is shown in Table 4 (the north finder can respond to control commands after self-test is completed).

Table 4 MSN300H High-Precision MEMS North Finder Host Computer Control Command Protocol

First Byte	Bytes	Signal Name	Dimension/Unit or Content	Equivalent	Interface Precision Description
1	1	Frame Header 1	Content: 55H	1	8-bit Unsigned Integer
2	1	Frame Header 2	Content: AAH	1	8-bit Unsigned Integer
3	1	Data Length	Content: 24H	1	8-bit Unsigned Integer
4	4	Loaded Longitude	[-180,180]deg	0.0000001	Little-Endian Format
5	4	Loaded Latitude	[-90,90]deg	0.0000001	Little-Endian Format
6	4	Loaded Altitude	m	1	IEEE 32-bit Float Little-Endian Format
7	4	Reserved 1	NA	1	-
8	2	Data Validity Mode	NA	1	bit0: 1 = LLA information valid; bit1: 1 = Loaded heading information valid; bit2: 1 = Alignment time valid bit3: 1 = Baud rate and period valid bit4: 1 = Installation misalignment angle valid bit5: 1 = Attitude angle write for transfer to navigation valid All bits are invalid when set to 0.
9	2	Reserved 2	NA
10	2	Reserved 3	NA
11	1	Output Baud Rate Configuration	NA	1	0：9600bps; 1:38400; 2：115200; 3:230400; 4:460800;
12	1	Output Period	NA	1	0：5ms 1:10ms 2：20ms; 3:50ms; 4:100ms; 5:200ms; 6:500ms： 7:1s; 8:2s; 9:5s;
13	2	2	(1)Roll Installation Misalignment Angle between INS and Target Point UsrTransRoll (2)Transfer to Navigation Roll Angle Roll	0.006	[-180~180] Whenbit4is1, and command is 0xAAcommand, this angle represents (1)Installation Misalignment Angle Whenbit5is1, and command is 0xBBcommand, this angle represents (2)Attitude Angle Written for Transfer to Navigation
14	2	2	(1)Heading Installation Misalignment Angle between INS and Target Point UsrTransYaw (2)Transfer to Navigation Heading Angle Yaw	0.006	Value range is[-180~180], therefore when writing the theoretical heading angle, north to east should be positive and north to west should be negative
15	2	2	(1)Pitch Installation Misalignment Angle between INS and Target PointUsrTransPitch (2)Transfer to Navigation Pitch Angle Pitch	0.006	[-180~180]
16	2	Reserved 4	NA
17	2	User Command	NA	1	16-bit Unsigned Integer; 0) 0x0000: No Command 1) 0x0011: Start Static Auto North Finding Command; 2) 0x0066: Write LLA to Flash Command; 3) 0x0077: Write Alignment Time to Flash Command; 4) 0x0099: Write Baud Rate and Output Frequency to Flash Command; 5)0x00AA:5) Write Attitude Installation Misalignment Angle to Flash Command; 6)0x00BB:Write Attitude Angle for Transfer to Navigation Other invalid values: Command not responded;
18	2	Alignment Time	[120,6553.5]	0.1	16-bit Unsigned Integer; (1) Under the static auto north finding command, the alignment time value is coarse alignment (30s) + fine alignment time, and the time should be no less than 120s.
19	1	Checksum	Lower 8 bits of the cumulative sum of all bytes from the data length (including data length) to before the checksum byte	1	Lower 8 bits of the cumulative sum of bytes at indices (2 to 38)

 

Precautions

• Please observe the product electrical interface definition. During use, strictly follow the terminal arrangement to avoid incorrect connections;
• The product is a precision measurement device. During handling, avoid subjecting it to shocks, collisions, or other conditions beyond the product's tolerance range;
• Please check the power supply before powering on the product. Do not use a computer USB port for direct power supply, as insufficient power may damage the product. Additionally, if you need to verify repeatability accuracy, the interval between power cycles shall not be less than 10s;
• The product installation has a significant impact on angular velocity measurement. To avoid introducing installation errors, the mounting surface must have good flatness;
• To ensure measurement accuracy, the product must be mounted securely and firmly to avoid loosening that could introduce measurement errors;
• During product installation and operation, ESD protection should be observed. It is recommended to wear an ESD wrist strap;
• Please strictly follow the requirements of this manual for operation. Confirm that the external environment matches the operating requirements. If problems occur, do not open the product cover or modify the internal structure. If any issues arise, please contact our technical support team promptly.

 

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