Watson Industries, Inc.
DMS-SGP01 Rev B 03/22/2018
6
Track Heading is directly from the GPS reference.
Angular Rate Sensors bias corrections are not updated.
The reference mode can be selected either through the terminal mode, or by an analog logic
command. Note that reference mode is never a default setting. It must be re-selected when re-
powering the unit.
Free Mode
While in Free Mode, the DMS will output data from the sensors without correction by the
references. For example, the Bank Angle data output in Free Mode is calculated directly from the
X-axis Rate Sensor. In this case, the angle is a direct integration of the roll rate. Free Mode can be
used to totally reject effects from dynamic accelerations, but accuracy degrades with time. It is
intended for use over periods of up to a minute at a time. This mode provides sensor information
similar to normal operation mode with the following differences:
Bank, Elevation and Heading are obtained directly from the rate sensors alone.
Relative Heading from last known heading is used.
Angular Rate Sensors bias corrections are not updated.
Free mode can be accessed either through terminal mode, or by an analog logic command. Note
that free mode is never a default setting. It must be re-selected when re-powering the unit. The
user should not enter free mode until after the DMS is initialized and its readings are stable.
Hold Mode
This mode inhibits bias adjustments to the rate sensors. It is intended for short-term use only since
leaving biases uncorrected will allow errors to accumulate over time. The accumulating bias error
will result in small attitude errors. Hold mode can provide better performance in highly dynamic
environments such as continuous circling over several minutes time. The user should not enter hold
mode until after the DMS is initialized and its readings are stable.
Control Mode
In this mode, the DMS will output sensor data normally unless it receives a control mode
command. Once a command is received, the DMS will send data in response and await the next
command. Using this mode, the user can retrieve the EEPROM map, adjust baud rates, adjust
output formats, and many other operational settings of this sensor. Having access to this
information makes the Control Mode useful in assisting the factory to remotely troubleshoot
operational problems that may occur. For more details, see the RS-232 Input Commands section
later in this manual.
Interface
The DMS has analog, digital logic, and digital serial interface capabilities.
RS-232 Output Format
The standard RS-232 output consists of a string of decimal ASCII characters sent asynchronously
at regular intervals. Nominally, the string is sent at 9600 baud with eight data bits, one stop bit and
no parity. The mating connector for the RS-232 is a 9 Pin Male D-Sub. The RS-232 signal is
referenced to signal ground. The number of strings sent per second depends on the baud rate and
the output format. The maximum rate is 71.11 strings per second. See Appendix A for information
on how to change the data string. The contents of a typical string are formed as follows:
