Watson Industries, Inc.
DMS-EGP01 Rev A 02/12/2015
10
Analog Inputs
In an effort to make this system more versatile, the DMS allows the user to input analog data that
can then be added to the serial data output. This allows the system to act as a data acquisition unit
for other vehicle information such as engine RPM, engine temperature, fuel remaining,
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 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.
The digital signal that the DMS can receive is from the GPS module.
Output Logic Commands
Initialization lasts 4 seconds, during which time the "Ready" signal is set low (0v). Once
Initialization is complete, the "Ready" signal is set high (+5VDC). The ready signal is on pin 9 of
the 25 pin connector.
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 a 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) Coast (Free Inertial) – 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 analog digital inputs are all disabled if any equivalent serial command is sent via RS-
232. This is to prevent hardware/software conflicts.
