Sensors Overview

Most of Galileo's sensor modules are based on a motherboard/daughter card configuration. The motherboards provide power, the CAN bus interface, and ADC channels for up to four daughter cards. The daughter cards provide external interfaces to thermocouples, pressure sensors, and other data collection devices, and provide the signal shaping required to feed those signals into the motherboard's ADC channels.

There are two motherboards available. "senshi" provides 16-bit resolution on its inputs along with support for differential signals at an approximately $35 construction cost. "senslo" provides only 10 bits of resolution and only allows single-ended signal inputs, but is much less expensive at approximately $12. It is thus appropriate for signals that do not require much resolution, such as measuring bus voltage.

Daughter cards are share the same footprint and are thus interchangeable, allowing a high degree of customization. For instance, in an aircraft with two batteries and two alternators, it may be desirable to install two current and two voltage daughter cards in one module to monitor these busses. In a single bus configuration, the unused channels could be replaced with thermocouple interfaces to collect engine temperature data or other sensor inputs. Also, because each module may hold up to four daughter cards, sensor modules may be deployed in excess to allow for future expansion. When the time comes to upgrade, the additional daughter cards may be simply plugged into the modules and the system will automatically start using them.

Note that daughter cards that may be installed on a senslo motherboard may be installed on a senshi motherboard as well. Not all daughter cards designed for senshi may be installed on a senslo board, however, even if the extra resolution is not required, because some of the more complex modules (such as the magnetometer) require senshi's differential signal support.