2.5.6 External Sensor Unit (ESU)

The purpose of the ESU is to measure the output of the sensor systems that are located within the propulsion module, and report the data to the main processor. Current propulsion module sensors are the three axis magnetometer, and the depth sensor. The Three Dimensional Acoustical Positioning System, or 3DAPS, is currently under development, and will eventually be integrated into the ESU. 3DAPS will provide data about Ranger NBV's position and attitude to the main processor.

Figure 2-23 The External Sensor Unit

The ESU contains several different components. The magnetometer triad is located within the ESU housing itself. The depth sensor is located in the upper starboard front of the propulsion module. Signals from both of these sensors are obtained and transferred to the 6811 LPU by way of a 12 bit, 8 channel ADC board. This data stream is then returned to the main processor by way of an RS422 serial interface. This data is returned to the main processor at a rate of 220 Hz. Eventually, the 3DAPS receiver board will be interfaced to the ESU 6811 LPU, and will receive the signals form a hydrophone array located on the propulsion module. These signals will be captured, ranges calculated and processed, and returned to the main processor.
The ESU is located in the lower rear propulsion module.