Creating a Fault Insertion Unit (FIU) Module With the NI PXI-2586

Fault Insertion Units (FIUs) are designed to insert fault conditions between automated test equipment and devices under test (DUTs).  In a FIU’s default setting, DUT signal lines are connected to the test equipment directly through the FIU module.  To insert a fault condition, the unit configures internal relays to create short-circuit connections and open circuits.  The following are fault conditions commonly used in today’s automated test applications:

1. Open Circuit Fault – DUT signal line disconnects from the test fixture.
2. Short Circuit Fault –
   1. Pin to Pin Short – DUT signal line connects to one or more other DUT signal lines.
   2. Between DUT Line and External Fault Line – DUT signal line connects to a fault insertion line.  Fault insertion lines connect to power supply lines, system grounds, etc.

One or more NI PXI-2586 General Purpose Switch modules can be used to create a variety of different 12A Fault Insertion Unit (FIU) topologies.  This white paper shows how to create and use the following topologies: a 3-channel FIU with 2 fault buses, a 4-channel FIU with 1 fault bus, and a 9-channel FIU with 1 fault bus (requires 2 PXI-2586 modules). NI also offers a range of PXI Signal (Fault) Insertion Switch Modules

Using the NI PXI-2586 to Create a 12 A FIU Module

The NI PXI-2586 is a high-power, general-purpose switch in a single-slot, 3U PXI module.  It has 10 independent SPST (Form A) relays, as can be seen in Figure 1, with low contact resistance and high isolation voltage.  The module is rated for both high currents (up to 12 A) and high voltages (up to 300 VDC/300 VAC), and is ideal for switching power signals and loads in control applications and battery, power supply, and automotive testing.

Figure 1: NI PXI-2586 Power-On State
 

One or more NI PXI-2586 modules can be used to create a variety of different 12 A FIU topologies.  This white paper shows how to create and use the following topologies:

• 3-channel FIU with 2 fault buses
• 4-channel FIU with 1 fault bus and the ability to select between two external fault conditions
• 9-channel FIU with 1 fault bus and the ability to select between two external fault conditions (requires 2 NI PXI-2586 modules)

The topologies are created by externally connecting the NI PXI-2586 channel and COM pins.  The connections between pins can be made when assembling your cable harness or can be managed on any custom fixture or PCB required for your DUT. 
 

3-Channel FIU with 2 Fault Buses

One NI PXI-2586 10-Channel, 12 A SPST switch module can be used to create a 3-channel FIU with the ability to apply 2 simultaneous fault conditions.  Figures 2 through 5 show the resulting 3-channel FIU’s default configuration, as well as the FIU’s open and short circuit fault conditions.

Figure 2: 3 Ch, 12 A FIU with 2 Fault Buses - Default Configuration



Figure 3: Open Circuit Fault – DUT 0



Figure 4: Pin to Pin Short – DUT 0 and DUT 2



Figure 5: External Fault (such as Vbatt or GND) – DUT 0 and FAULT 1

Connect the channel and COM pins of the NI PXI-2586 as shown in Table 1 and Figure 6 to build the 3-channel FIU topology:

Pins to Short	Color in Pinout
Ch0, Ch5, COM7	Red
Ch1, Ch4, COM8	Yellow
Ch2, Ch3, COM9	Green
COM0-2	Blue
COM3-6	Purple

Table 1: 3-Ch FIU - Pins to Short (Table)


Figure 6: 3-Ch FIU - Pins to Short (Diagram)
 

4-Channel FIU with 1 Fault Bus

A single NI PXI-2586 module can also be used to create a 4-channel FIU with the ability to select between two external fault conditions.  Figure 7 shows the 4-channel FIU’s default configuration.

Figure 7: 4-Ch FIU with 1 Fault Bus, 2 Selectable External Faults - Default Configuration
 

To build a 4-channel FIU with 1 fault bus and the ability to select between two external fault conditions, short-circuit the channel and COM pins as shown in Table 2 and Figure 8.

Pins to Short	Color in Pinout
Ch6, COM0	Red
Ch7, COM1	Yellow
Ch8, COM2	Green
Ch9, COM3	Purple
COM4-9	Blue

Table 2: 4-Ch FIU - Pins to Short (Table)
 

Figure 8: 4-Ch FIU – Pins to Short (Diagram)
 

9-Channel FIU with 1 Fault Bus

Create a FIU with more channels by using multiple NI PXI-2586 modules.  Two NI PXI-2586 modules can be used to create a 9-channel FIU with 1 fault bus and the ability to select between two external fault conditions.  Figure 9 shows the 9-channel FIU’s default configuration.

Figure 9: 9-Ch FIU with 1 Fault Bus, 2 Selectable External Faults - Default Configuration
 

To build a 9-channel FIU with 1 fault bus and the ability to select between two external fault conditions, use 2 NI PXI-2586 modules and short-circuit the channel and COM pins as shown in Table 3 and Figure 10.

Pins to Short	Color in Pinout
Ch6A, COM0A	Red
Ch7A, COM1A	Yellow
Ch8A, COM2A	Green
Ch9A, COM3A	Purple
Ch5B, COM4B	Blue (Ring)
Ch6B, COM0B	Red (Ring)
Ch7B, COM1B	Orange (Ring)
Ch8B, COM2B	Green (Ring)
Ch9B, COM3B	Purple (Ring)
COM4A-9A, COM5B-9B	Blue

Table 3: 9-Ch FIU - Pins to Short (Table)


Figure 10: 9-Ch FIU - Pins to Short (Diagram)
 

Note that there are COM pins from both devices that are to be connected together.  Additionally, note that the same-colored solid and ringed pins are not to be connected together.