Watson Industries, Inc.
DMS-SGP02 Rev K 03/22/2018
11
altitude/depth or any other important data. The four analog user inputs as well as the velocity input
have one megohm input impedance, 16 bit A/D conversion resolution, ±10 volt input range and
have a bandwidth of DC to 25 Hertz.
Speed Inputs
A vehicle speed input is used to assist in the correction of errors. It is also included in the
parameter set that is available for serial output. Although its use is not always required, it is highly
recommended that this signal be supplied to the DMS. The unit can receive speed information in
two formats, an analog or digital signal. The internal GPS receiving unit provides the digital
signal.
The optional analog speed input signal is a voltage that is scaled to 40 KPH per volt. Forward
motion should produce a positive signal with respect to signal ground. Many other velocity scale
factors can be handled through simple changes in the scale factor stored in the EEPROM in the
microprocessor. This can be done with a PC and the assistance of the factory.
Input Logic Commands
The DMS also has several digital inputs that are all activated by connecting to signal ground. The
user should only apply a ground because all the inputs have an internal pull-up resistor to +5VDC.
The pins are as follows:
a) Initialization - Resets all angle integrators. The unit should be in a non-accelerated
condition if this command is given. Leave pin open if not in use. Ground to command.
b) Reference - An alternate set of sensor information primarily intended as an
instrumentation mode. Leave pin open if not in use. Ground to command.
c) Free Inertial Mode – In this mode, the attitude is computed from gyro data only. Free
mode is used when extreme accelerations are expected. Leave pin open if not in use.
Ground to command.
NOTE: The digital logic inputs are all disabled if any one equivalent serial command is sent via
RS-232. This is to prevent hardware/software conflicts.
