Due to the End-of-Life (EOL) notice from our component supplier, the power switch for PSW-Series has been updated. This change specifically pertains to the mechanical operation and appearance of the power switch, as detailed below:

• Switch Functionality: The original power switch used in PSW-Series featured a relay-trip (hardware trip-off) function. Following the supplier's discontinuation notice, our engineering team initiated a second-source design transition. Since there is no direct drop-in replacement with the same trip function currently available, the new switch provides standard ON/OFF operation only.
  Note: While the User Manual was updated in September 2024 to reflect this change, some units manufactured in late 2025 may still be equipped with the original relay-trip switch due to a postponement in the supplier's final production cutoff.

• Specifications and Programming: There are no changes to the electrical specifications or the SCPI command set. All performance parameters remain fully consistent with the previous version.

• Protection Features: All core protection mechanisms, including OCP (Over-Current Protection), OVP (Over-Voltage Protection), and OPP (Over-Power Protection), remain fully functional.

• Physical Appearance and Operation:
  1. The power switch color is now Black.
  2. The hardware-controlled trip function has been removed (refer to the illustration below for visual comparison).

We appreciate your continued trust and support of GW Instek products.

Step 1: Check whether the AC input of the power supply is normal? Is it because the power strip controlled by the switch is forgot to turn on or was turned off by a colleague without being noticed. Check whether the display on the power supply has a display, if not, please check whether the fuse of the power supply is blown.

Step 2: After confirming that the power input is normal, set the output voltage and current of the power supply, both of which cannot be 0 (especially note that the current cannot be 0). If it is found that the setting value cannot be displayed, some GW Instek models provide a keyboard lock function to ensure that the setting value is not misused during the test. Please confirm whether the model you are using has this function. If so, please confirm that the Key Lock indicator is off, if the Key Lock light is on, please unlock it first. If the power supply still cannot be set, please confirm whether the power supply is connected to the computer. If the computer is connected, the remote control mode will cancel the Local operation.

Step 3: If the power supply has an output control switch, please press on. Power supply with an output control switch often has a light signal indicating that the output is turned on.

Step 4: If the output control switch is turned on and the light is not on (the light may be faulty, but the power supply still has output), please use the voltage range of a multimeter to measure the output of the power supply. There are several power supplies of GW Instek with on/off delay timer function. Please also check whether the output has a time delay because this function is turned on.


If the power supply still has no output after the above steps, please contact your nearest GW Instek Service Center to arrange for the instrument to be repaired. 

Service Support:
services@goodwill.com.tw

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.

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