DMU380ZA Series
User’s Manual
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Doc# 7430-3810 Rev.02
Page 13
After passing thru a digitally controlled programmable low-pass filter, the rate and
acceleration sensor signals are obtained at 200Hz. The sensor data is filtered by the
processor using FIR filters. The factory calibration data, stored in EEPROM, is used by
the processor to remove temperature bias, misalignment, scale factor errors, and non-
linearities from the sensor data. Additionally any advanced user settings such as axes
rotation are applied to the IMU data. The 200Hz IMU data is continuously being
maintained inside the IMU380ZA, and is available at 200Hz on the SPI output port
registers. Digital IMU data is output over the UART port at a selectable fixed rate (100,
50, 25, 20, 10, 5 or 2 Hz) or on as requested basis usi
ng the GP, ‘Get Packet’ command.
The digital IMU data is available in one of several measurement packet formats including
Scaled Sensor Data (‘S1’ Packet).
In the Scaled Sensor Data (‘S1’ Packet) data is output
in scaled engineering units. See Section 7 of the manual for full packet descriptions.
IMPORTANT
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, and thus, are subject to overflow (data type wrap around).
3.2.1
IMU380ZA Advanced Settings
The IMU380ZA advanced settings are described in Table 6. All of the advanced settings
are accessible thru NAV-VIEW under the Configuration Menu, Unit Configuration
settings. For a full definition of the SPI port please see section 5.
Table 6 IMU380ZA Advanced Settings
Setting
Default
Comments
Baud Rate
38,400 baud
9600, 19200, 57600 also available
Packet Type
S0
S1 also available
Packet Rate
100Hz
This setting sets the rate at which selected Packet Type, packets are output. If
polled mode is desired, then select Quiet. If Quiet is selected, the IMU380ZA
will only send measurement packets in response to GP commands.
Orientation
To configure the axis orientation, select the desired measurement for each
axis: NAV-VIEW will show the corresponding image of the IMU380ZA, so it
easy to visualize the mode of operation. Refer to Section 8.4 Orientation Field
settings for the twenty four possible orientation settings.
Filter Settings (5,
10, 20, 50 Hz)
20 Hz
The low pass filters are set to a default of 20 Hz for the accelerometers, and 20
Hz for the angular rate sensors. There is one filter setting for all three angular
rate sensors. There is one filter setting for all three accelerometers.
BIT
See 9.1
NOTE on Filter Settings
Why change the filter settings? Generally there is no reason to change the low-pass filter
settings on the IMU380ZA or other DMU380ZA Series Inertial Systems. However, when
a DMU380ZA Series product 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 IMU380ZA in the target environment and
reviewing the data with NAV-VIEW can be helpful to determine if changing the filter
settings would be helpful. Although the filter settings can be helpful in reducing vibration
based noise in the signal, low filter settings (e.g., 5Hz) also reduce the bandwidth of the
signal, i.e. can wash out the signals containing the dynamics of a target. Treat the filter
settings with caution.
