A typical FIU placement in a dynamic test system for an Engine Control Unit (ECU) is shown below.
The FIU is designed to insert fault conditions between the real-time hardware-in-the-loop (HIL) simulation systems and the ECU/Device Under Test (DUT).
To insert fault conditions, internal relays are configured to create short-circuit connections and open circuits. As mentioned above, automated test applications commonly use the following fault conditions:
- Open Circuits
- Short to Ground or Power
- Pin-to-Pin Short
FIUs with switchable fault bus inputs can be used to create additional fault conditions, such as a Pin-to-Pin Short Through a Load.
In an FIU’s no-fault setting, test equipment is directly connected to DUT signal lines through the FIU module.
Open Circuit Faults
In an open circuit or interrupt fault, the signal line between the test application and DUT is left open to determine how the DUT behaves after a signal interruption.
Short to Ground or Short to Power
To simulate shorts to ground or power, the signal line is connected from an external fault line or fault bus to the DUT. The fault buses can be configured to simulate power supply lines or system ground.
In a pin-to-pin short, the DUT signal line is connected to one or more additional DUT signal lines.
Example Pin-to-Pin Short Through a Load Using the NI PXI-2510
The NI PXI-2510 has two fault buses. Each fault bus has four switchable inputs to select among multiple fault conditions such as battery voltage (Vbatt), ground (GND), and other fault voltage potentials. The non-switchable input to each fault bus is intended for monitoring the fault bus with a DMM. The switchable fault bus inputs allow for another fault condition: a pin-to-pin short through a load.
The following example shows a pin-to-pin short through a load using the NI PXI-2510: