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18 Operation Overview
When programmed to a mode, a module remains in that mode until the mode is changed or until a fault condition, such as an
overpower or overtemperature, occurs. When changing modes, the module’s input is momentarily disabled (non-conducting
state) before the new mode is enabled. This insures that there will be minimum overshoots when changing modes.
The current, resistance, and voltage mode parameters described in subsequent paragraphs can be programmed whether or
not the mode is presently selected. When a mode is selected via the front panel or via the GPIB, most of the associated
parameters will take effect at the input (exceptions are noted in the mode descriptions).
Constant Current CC (Mode)
In this mode, the module will sink a current in accordance with the programmed value regardless of the input voltage (see
Figure 2-2). The CC mode can be set with front panel keys(
, , and ) or via the GPIB
(MODE:CURR command). The CC mode parameters are discussed in the following paragraphs.
Figure 2-2. Constant Current Mode
Ranges
Current may be programmed in either of two overlapping ranges, a low range and a high range. The low range provides
better resolution at low current settings. The range can be set at the front panel (
and ENTRY keys) or via the
GPIB (CURR:RANG command). Any value in the low range selects the low range. Any value above the maximum of the
low range selects the high range. Changing the range affects the module in the same manner as changing modes; i.e., it
causes the input to go through a non-conducting state. Note that the values of the present current settings may be
automatically adjusted to fit the new range. For example, if 10 A is the present setting and the 0 to 6 A range is then
programmed, the current setting will automatically be changed to 6 A; see Chapter 4 - Local Operation.
Immediate Current Level
The current level can be set at the front panel (
and ENTRY keys) or via the GPIB (CURR command). If the CC
mode is the active mode, the new setting immediately changes the input at a rate determined by the slew setting (described
below). If the module is not in the CC mode, the new setting is saved for use when the mode is changed to CC.
Triggered Current Level
The current level can be preset (stored in the Electronic Load) allowing the input to be updated when a trigger is received
instead of immediately as described above. The current level can only be preset via the GPIB (CURR:TRIG command).
The preset capability is not available at the front panel.
If the CC mode is the active mode, the preset current level will become the actual value and the input will be updated when
a trigger occurs. If the CC mode is not the active mode, the preset current level will become the actual value when a trigger
occurs but there will be no effect on the input until the CC mode becomes active. Once a level is triggered, subsequent
triggers will have no effect on the input unless another CURR:TRIG command is sent. The trigger sources available to the