Agilent Technologies 66309B, D, 66311B, 66111A External Protection Connections, FLT/INH Examples

3 - Installation

External Protection Connections

This rear panel connector, has a fault output port and an inhibit input port. The fault (FLT) output, also referred to as the DFI (discrete fault indicator) signal in the front panel and SCPI commands, is an open collector circuit that pulls the positive output low with respect to the negative (chassis-referenced) common. The high impedance inhibit (INH) input, also referred to as the RI (remote inhibit) signal in the front panel and SCPI commands, is used to shut down the dc source output whenever the INH + is pulled low with respect to the INH (chassis-referenced) common.

The connector accepts wires sizes from AWG 22 to AWG 12. Disconnect the mating plug to make your wire connections.

NOTE: It is good engineering practice to twist and shield all signal wires to and from the digital connectors. If shielded wire is used, connect only one end of the shield to chassis ground to prevent ground loops.

Figure 3-10 shows how you can connect the FLT/INH circuits of the dc source.

In example A, the INH input connects to a switch that shorts the Inhibit pin (+) to common whenever it is necessary to disable output of the unit. This activates the remote inhibit (RI) circuit, which turns off the dc output. The front panel Prot annunciator comes on and the RI bit is set in the Questionable Status Event register. To re-enable the unit, first open the connection between pins INH + and common and then clear the protection circuit. This can be done either from the front panel or over the GPIB.

In example B, the FLT output of one unit is connected to the INH input of another unit. A fault condition in one of the units will disable all of them without intervention either by the controller or external circuitry. The computer can be notified of the fault via a service request (SRQ) generated by the Questionable Status summary bit. Note that the FLT output can also be used to drive an external relay circuit or signal other devices whenever a user-definable fault occurs.

		NOTE: Connectors			4 3 2 1
			are removable
				INH	FLT
			4 3 2 1	. . . .
					FLT
				+	Output
					- +
INH	FLT		Switch	INH
				Input
. .	.	.	(Normally
			Open)
+	-	+	INH Input		4 3 2 1
			INH Common
				INH		FLT
				Input
						Output
			A) INH Example with One Unit		B) FLT Example with Multiple Units

Figure 3-10. FLT/INH Examples

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