AFDAU-T1 Aerial Firefighting
Data Acquisition Unit
Installation Manual
AMS-IM-1-01 Rev. 7
22 September 2021
18
Discrete Sensors
2.3.1 Overview
The AFDAU-T1 provides 12 inputs for discrete sensor connections, 6 of these being internal relays and 6 being
ground seeking general purpose inputs. These inputs can be configured as various airframe and firefighting
equipment inputs using the AFDAU Configuration Tool.
The following discrete sensors can be connected to the discrete inputs of the AFDAU-T1
•
Engine Start/Stop Switch
•
Take-off/Landing
•
Container Door Open
•
Additive Pump On/Off
•
Additive Select
•
Container Select
•
Landing Gear Stowed/Deployed
2.3.2 Relays
Six relays, K1 through to K6 are provided for connection of discrete sensors and it is up to the installer to determine
the suitability of using the relays as oppose
d to the General Purpose Inputs (GPI’s, see below) for each discrete
sensors case. Each relay coil is presented on the AFDAU-
T1’s Main D37 Pin connector and features a diode in
parallel across the coil and another in series with the ground pin. It is important during installation that the polarity of
the relay pins is observed wired up correctly.
There are two ways in which to use the relays, by switching the ground pin or by switching the power pin as
demonstrated below:
EXAMPLE: GROUND SWITCHED RELAY
EXAMPLE: POWER SWITCHED RELAY
AFDAU-T1
DISCRETE
SIGNAL
PROCESSOR
+28vdc
Discrete Sensor
K1-K6
AFDAU-T1
DISCRETE
SIGNAL
PROCESSOR
+28vdc
Discrete Sensor
K1-K6
