Moog Crossbow NAV440 Series - Manual (Page 24)

NAV440 User Manual
7430‐0131‐01 Rev. F
Page 24
Digital IMU440 data is output over the RS‐422 at a selectable fixed rate (100, 50, 25, 20, 10, 5 or 2 Hz) or as
requested using the GP (Get Packet) command.
The digital IMU440 data is available in one of several measurement packet formats including Scaled Sensor Data (S1
Packet) and Delta‐Theta, Delta‐V (S2 Packet). In the Scaled Sensor Data (S1 Packet) data is output in scaled
engineering units. In the Delta‐Theta, Delta‐V format (S2 Packet) scaled sensor data is integrated with respect to
the time of the last output packet and the data is reported in units of accumulated (i.e., delta) degrees and
meters/second. For details about full packets, refer to Chapter 9. Communicating with the 440 and Chapter 10.
Programming Guidelines.
NOTE: The Delta‐Theta, Delta‐V packet is only recommended for use in continuous output mode at 5Hz or greater.
Polled requests for this packet will produce values accumulated since the last poll request; they are subject to
overflow (data type wrap around).
IMU440 Advanced Settings
The IMU440 advanced settings are described in below. All of the advanced settings are accessible thru NAV‐
VIEW 2.2 under the Configuration Menu→Unit Configuration settings. For information about using NAV‐VIEW 2.2,
refer to
Table 5
Chapter 7. Configuring the 440 Series with NAV‐VIEW 2.2.
Table 5IMU440 Function Advanced Settings
Setting Default Value Comments
Baud Rate 38,400 9600, 19200, 57600 also available
Packet Type S1 S2 also available
Packet Rate 100Hz This sets the rate at which the selected Packet Type packets are output. If
polled mode is desired, then select Quiet. If Quiet is selected, the unit will
only send measurement packets in response to GP commands.
Orientation See Figure 4 on
page 22. To configure the axis orientation, select the desired measurement for each
axis: NAV‐VIEW 2.2 will show the corresponding image of the unit, so it easy
to visualize the mode of operation. Refer to Orientation Field on page 84 for
the twenty four possible orientation settings. The default setting points the
connector AFT.
Analog Filter
Clocks 1,2, 3 25 Hz The low pass filters are set to a default of 25 Hz for the accelerometers, and
25 Hz for the angular rate sensors. There is one filter setting for all three
angular rate sensors. There are two settings for the accelerometers, one for
the X and Y axes, and a separate setting for the Z axis. In many installations,
the Z‐axis vibration level is much higher than in the X and Y axes; in such
cases it can prove helpful to filter the Z‐axis at a lower cutoff than the X and Y
axes. For more information, Analog Filter Clocks below.
Analog Filter Clocks
Typically, there is no reason to change the low‐pass filter settings on the IMU440 or other 440 Series Inertial
Systems. However, when a 440 Series unit is installed in an environment with a lot of vibration, it can be helpful to
reduce the vibration‐based signal energy and noise prior to further processing on the signal. Installing the IMU440
in the target environment and reviewing the data with NAV‐VIEW 2.X can be helpful to determine if changing the
filter settings is needed. Although the filter settings can be helpful in reducing vibration based noise in the signal,
ce the bandwidth of the signal, i.e. can wash out the signals containing the
clock settings are shown in default IMU440 coordinate system.
low filter settings (e.g., 1Hz) also redu
dynamics of a target. The analog filter
Treat the filter settings with caution.