User manual

LABKON Series
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GMC-I Messtechnik GmbH 51
When the load RL is less than RC, the output current will dominate since the voltage will be less than the set voltage. The
power supply is said to be in constant-current mode. The load at point B has a relatively low resistance, the output voltage is
less than the voltage setting, and the output current is at the current setting. The supply is in constant-current (CC) mode and
the voltage setting acts as a voltage limit.
5.4 Unregulated State
If the power supply goes into a operation mode that is neither CV nor CC, the power supply is in unregulated mode, which
may occur momentarily. In this mode the output voltage and current are not predictable. The unregulated condition may be
the result of the input AC voltage below the specifications or caused by non-resistive load. For example, when the output is
programmed for a large voltage step, the output capacitor or a large capacitive load will charge up at the current limit setting.
During the ramp up of the output voltage the power supply will be in the unregulated mode. During the transition from CV to
CC as the output is shorted, the unregulated state may occur briefly during the transition.
5.5 Unwanted Signals
An ideal power supply has a perfect current or voltage output with no signals across the terminals or from the terminals to
earth ground. The actual power supply has finite noise across the output terminals and finite noise from either terminal to
earth ground. And the noise across the output terminals is of very low value in the GOSSEN METRAWATT LABKON Series.
The noise from the terminals to earth ground can be a problem for very sensitive circuitry that is referenced to earth ground.
When a circuit is referenced to earth ground, a low level line-related AC current will flow from the output terminals to earth
ground. Any impedance to earth ground will create a voltage drop equal to the current flow multiplied by the impedance. To
minimize this effect, the output terminal can be grounded at the output terminal. Alternately, any impedance to earth ground
should have a complementary impedance to earth ground to cancel generated voltages.