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CAUTION!
Watson Sensors are rugged devices that have been used successfully in a number of harsh
environments. The components have been qualified to withstand a mechanical shock of 500g 's or
greater, and most enclosures provide an added level of protection. However, dropping a sensor
from waist height onto a hard floor can cause a shock level of 600g's. At this level, damage is
likely to occur.
Introduction
The Dynamic Measurement System (DMS) is a solid-state sensor that provides the user with
dynamic measurements of angular attitude and angular rate, together with linear acceleration, in
three (3) mutually perpendicular planes (see Figure 3). A unique feature is the two sets of
acceleration measurements. One set gives sensor acceleration with respect to the sensor mounting
face while the other set resolves the motion into horizontal and vertical components, irrespective of
the sensor attitude. This allows the earth's gravitational field to be isolated from the measurement
of sensor motion. This System consists of a DMS unit with an internal GPS module and two
external GPS antennas.
Product Description
Watson Industries DMS uses solid-state angular rate sensors and silicon accelerometers. Interface
to the microprocessor is done through a 16-bit A/D converter. The solid-state angular rate sensors
used in this system provide high reliability, excellent performance, and low cost. There are no
physical adjustments required by the user. All of the primary transducers are locked into position
during manufacture. Adjustments are made with the aid of PC-based maintenance software, which
communicates with the DMS via the RS-232 serial connection. Calibration is achieved by using
the maintenance software to store data in non-volatile memory within the DMS. The DMS-SGP02
differs from a "standard" DMS with the addition of a Dual Antenna GPS System. This allows the
DMS to output True North heading instead of relative heading. The GPS receiver also provides a
vehicle velocity that is used to improve accuracy in high dynamic environments. This unit outputs
Latitude & Longitude based on the position of the aft antenna.
This unit will operate in three heading modes. The unit operates in True North heading mode ("G"
label header on output message) when in dual antenna GPS is valid. When dual antenna GPS signal
is lost then unit will switch to Track Heading mode ("T" label header on output message). When
dual antenna GPS is restored, the unit reverts to True North Heading. In the event of loss of the
GPS signal, the unit switches to relative heading ("I" label header on output message) based on the
last accurate GPS heading. When GPS signal is restored, the unit reverts to Track heading and then
to True North heading when dual antenna GPS is restored. The user may select to hold the unit in
relative heading mode full time. (See Appendix A Setting Velocity & Heading Modes)
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 ordinarily acquires this data from
the GPS system but is user configurable to acquire velocity from an analog input. The analog
signal 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.
Watson Industries, Inc.
DMS-SGP02 Rev K 03/22/2018
3
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