Operating Instructions; Operating Controls; Current Limit Control - HP 6960A Operating And Service Manual

Model 6960 A
SECTION III
OPERATING INSTRUCTIONS
Section III
3-1 Operating Controls
Figure 3-1 shows the functions of the front panel controls and terminals and is
self-explanatory.
3-2 To turn the instrument on, push in either of the range buttons, according to the voltage
and current which is desired. Accidental setting of both buttons, 18 V and 36 V, will
cause no damage to the unit; in this case the instrument has been switched to the
36 V - 300 mA range. Pushing in the button marked OFF turns the instrument off.
3-3 Current Limit Control
3-4 This knob adjusts the peak current output of the supply. The indication is nominal. To
set the value exactly, remove the load and short the power supply terminals. Adjust the .!i. . . . m
CURRENT LIMIT control until the meter indicates the required maximum current.
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If the supply is to be used in an application where the current drown from the
instrument is not essentially unifotm with respect to time, e.g. in pulse type
circuits, then the fast acting character of the current limiting circuit must be
taken into consideration. The average current may be within the supply rating
or below the maximum current set with the CURRENT LIMIT control, but peak
currents moy be high enough to cause the supply to clip. The CURRENT LIMIT
control must, consequently, be set to a value which is greater than the peak
current requirements of the circuit.
The output terminals are connected internally to a 200 juF capacitor which
helps supply high current peaks, provided they are of short duration. Any exter-
nal capacity added will improve the peak current capability, but will decrease
the safety provided by the current Iimit control. High range currents may then
destroy external components before the average current inside the supply
;11'
increases sufficiently to cause the limiting circuit to operate.
3-1