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Power Supply Function

Note that when the output voltage reaches the upper limit, the unit no longer op-

erates in constant current mode and the output current is no longer held con-

stant. Instead, the unit will now regulate the output voltage at its voltage limit

setting.

As shown by the horizontal portion of the shaded quadrants, when the unit is

sinking power, the output current may continue to increase in the negative direc-

tion as more current is forced into the unit. This can happen when the instru-

ment is connected to an external device such as a battery, and its output

voltage is higher than the voltage limit setting of the instrument. Once the cur-

rent exceeds the built-in negative over-current limit, the output will shut down. In

such a case, it is important to set the voltage limit properly in order prevent this

protection shutdown.

How to Set

The procedures to set the output priority mode are as follows.

1. Press the composite keys [Shift]+[V-set] (Config) on the front panel to enter

the configuration menu.

2. Select Mode and press [Enter] to enter into the setting interface.

3. Select CC or CV, and press [Enter].

Enter the setting interface of the loop response speed.

4. Select High or Low, and press [Enter].

At this point, return to the Config menu settings interface.

5. Rotate the knob to set the voltage/current rise time. When finished, press

[Enter].

6. Set the other Config menu items in the same way.

7. Set the output voltage and current value.

• CV priority

a. Press the [V-set] key on the front panel to set the output voltage val-

ue Vs.

b. Press the [I-set] key on the front panel to set the current upper limit I

+. Press [I-set] again to set the current lower limit I-, i.e. the negative

current limit value.

• CC priority

a. Press the [I-set] key on the front panel to set the output current value

Is.

b. Press the [V-set] key on the front panel to set the voltage upper limit

Vh, and press [V-set] again to set the voltage lower limit Vl.

ITech IT-M3900C Series User Manual

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