Agilent Technologies 6032A, 6035A, 6028A, 6033A, 603xA Remote Voltage Sensing, Foldback Protection

Foldback Protection

In some applications either CV or CC mode may be regarded as an error condition. The foldback protection feature protects sensitive loads by disabling the power supply output if the unit switches to the prohibited mode.

In local control, foldback protection is toggled on or off by the FOLDBACK pushbutton switch. The output will be disabled if the power supply switches from whichever mode (CV or CC) is in operation when foldback is enabled to the other mode. In addition to turning foldback protection on and off, the FOLDBACK pushbutton switch also resets the foldback protection circuit if it has tripped. The conditions which caused foldback should be corrected before the circuit is reset, or the foldback protection circuit will trip again after reset.

NOTE	If the foldback protection circuit has tripped and you want both to reset the circuit and disable foldback
	protection, you must press the FOLDBACK switch twice in rapid succession, once to reset the foldback
	protection circuit and the second time to turn off foldback protection before it trips again.

The green FOLDBACK ENABLED LED lights to indicate that foldback protection is enabled; the yellow FOLDBACK LED lights to indicate that the foldback protection circuit has tripped. Note the ERROR LED will light if an attempt is made to turn on foldback protection while the power supply is not in CV or CC mode.

When enabled via GP-IB foldback protection can be enabled for either mode, regardless of the operating state of the power supply when the command is received.

Remote Voltage Sensing

Because of the unavoidable voltage drop developed in the load leads, the strapping pattern shown in Figure 3-4 will not provide the best possible voltage regulation at the load. The remote sensing connections shown in Figure 3-6 improve the voltage regulation at the load by monitoring the voltage there instead of at the supply’s output terminals. Remote sensing allows the power supply to automatically increase the output voltage and compensate for the voltage drops in the load leads. This improves the voltage regulation at the load, and is especially useful for CV operation with loads that vary and have significant load-lead resistance. Note that with remote sensing, voltage readback is at the load. Remote sensing has no effect during CC operation. When using remote sensing, turn off the power supply before changing the rear-panel straps, sense leads, or load leads. Connect the unit for remote voltage sensing by connecting load leads from + OUT and - OUT terminals to the load, disconnecting straps between + Out and + S and between - Out and - S, and connecting sense leads from the + S and - S terminals to the load as shown in Figure 3-6.

NOTE	Sensing is independent of other power supply functions; either local or remote sensing can be used
	regardless of how the power supply is programmed.

The load leads should be of the heaviest practical wire gauge, at least heavy enough to limit the voltage drop m each lead to

0.5volts. The power supply has been designed to minimize the effects of long load-lead inductance, but best results will be obtained by using the shortest load leads practical.

NOTE	Remote voltage sensing compensates for a voltage drop of up to 0.5 V in each lead, and there may be up
	to a 0.12 V drop between the -output terminal and the internal sensing resistor, at which point the OVP
	circuit is connected. Therefore, the voltage sensed by the OVP circuit could be as much as 1.12 V more
	than the voltage being regulated at the load. It may be necessary to readjust the OVP trip voltage when
	using remote sensing.

Operating Instructions 39