The DC mode of the AC power supply does not have the constant current (CC) output of the DC power supply.

The DC mode of the AC power supply can only provide a constant voltage (CV) output. When the DC power supply is overloaded, it will become a constant current (CC) output. When the DC mode of the AC power supply is overloaded, the output will stop.

The output of most DC power supplies is to provide a set voltage, which we call the constant voltage mode (CV mode). It is better to use "set fixed output voltage" to describe the overall meaning. At this time, the current of the power supply varies with load change.

However, this fluctuating current cannot exceed the maximum design current of the power supply (to meet the application and price design goals) or the maximum set current (to protect the circuit under test), so once the load current exceeds any of the above current values, the output of the power supply will switch from CV mode to constant current mode (CC mode)

Take the DC power with the maximum design voltage/current of 30V/3A as an example: when the load does not exceed 3A, the power supply is in constant voltage mode, and the set output voltage can be 0~30V (according to the minimum set resolution). Taking 12V as an example, as long as the load does not exceed 3A, the ideal output voltage is a fixed 12V (the unideal value is affected by the output accuracy, ripple/noise, linear regulation, load regulation), and the current value varies with load change.

Once the load exceeds 3A (according to Ohm's law 12V/3A=4 ohms, when it is lower than 4 ohms, the load will exceed 3A), since the power supply can only provide 3A, it will be converted to constant current mode at this time, the current is 3A, the output voltage varies with load change.

The relationship between load, current and resistance is as follows: Generally, the reason why the current does not reach the set current is that the resistance is not small enough.

Large load = large current = small resistance; small load = small current = large resistance

How to set the maximum current:

Knob-type setting: The output must be short-circuited to see the current reading. It is recommended to turn the knob to the state where the current is 0. If the knob is at the maximum current position, there may be sparks when the output is short-circuited (possibly frightened). Slowly turn the knob from the position where the current reading value is 0 to the desired maximum setting current.

Key-press setting: Just use the numerical and unit keys to input the required maximum setting current.

Application keywords: constant current output, constant current output

The launch of GSM-20H10 is to provide users with a more economical choice on the entry-level Source Measure Unit.

Therefore, we also take into account users’ requirements to replace the instrument. Therefore, all the commands on Keithley 2400 can be recognized and executes by GSM-20H10.

But there are two special cases users must consider:

1. GSM-20H10 is much faster than Keithley 2400 in terms of the speed of CPU processing. When the test system is very sensitive or strict to command sequence, time adjustment on commands may be necessary.
2. Keithley uses some unpublished commands in the software, which limit the direct replacement of GSM20H10.

When the output Current level exceeds 3A, the overload indicator turns red and CH3 operation mode switches from Constant Voltage to Constant Current. Note:"overload"in this case does not mean an abnormal operation please remove your load then overload indicator would be turns off if you have higher voltage and current requirement you can shift to CH1 or CH2 for operating.

The LOCK key to lock the front panel key operation. When the LOCK key function enable that the LED turns on. To unlock, press the LOCK key for 2~3 seconds then the key LED will be turn off.

Make sure you are NOT connecting the load wire to the remote sensing terminal. Please Refer our user manual page30 for connection details.

The cable loss might be causing the load voltage lower than the setting. Upgrade the output cable to a better capacity or use the remote sense to compensate for the voltage drop. Please refer user manual.

After editing OVP value and OCP status, press the (Vset/Iset/Enter) key to confirm. Otherwise the setting does not change.

The following scenarios are possible:The following scenarios are possible:

• Make sure the rear panel OVP setting is in the “Normal” position. If the OVP switch is in the “SET” position, the meter might show the OVP setting, not the output value. For OVP details, please refer user manual page22.
• If you are using Channel 1 or Channel 3, make sure the meter switch on the right side is in the correct position. Channel 1 and 3 share the same meter.

This indicates there is an internal error. Please Contact the service center.

Storing and Recalling Operating:

(1)The storing setting function including the store of the Output range, Output voltage value, Output current value, Over Voltage protection level, Over Current protection level, Over Voltage protection status, Over Current protection status and the Delay time.
(2)Store the present setting status to the memory bank: Press [SHIFT][STORE], set the panel operation to Storing setting selection, input the memory address by using number key (When want to correct the input value due to error key-in, can use wheel knob to clear the error value and re-input the value), then press [ENTER] to complete the change of store, and the panel will display “DONE” message.
(3)Recall the setting status from the memory bank: Press [SHIFT][RECALL], set the panel operation to Recall setting, use the number key to recall the desired memory address (When want to correct the input value due to error key-in, can use wheel knob to clear the error value and re-input the value), then press [ENTER] to complete the change, and the panel will display “DONE” message.