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Q1 gw_product_detail_bar.png gw_product_detail_bar.png What are the steps to check if the power supply has no output?

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:

Q2 gw_product_detail_bar.png gw_product_detail_bar.png Keithley 2400 is a widely used Source Measure Unit in the market. Does GSM-20H10 provide compatible commands?

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.



Q3 gw_product_detail_bar.png gw_product_detail_bar.png The CH3 overload indicator turned on is this error?

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.

Q4 gw_product_detail_bar.png gw_product_detail_bar.png What is the key lock function of the GPD-3303S / GPD-3303D?

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.

Q5 gw_product_detail_bar.png gw_product_detail_bar.png The load wire does not fit into the terminal.

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

Q6 gw_product_detail_bar.png gw_product_detail_bar.png The actual output is lower than the setting.

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.

Q7 gw_product_detail_bar.png gw_product_detail_bar.png The OVP value/ OCP status has not been changed.

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

Q8 gw_product_detail_bar.png gw_product_detail_bar.png The meter does not match the real value.

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.

Q9 gw_product_detail_bar.png gw_product_detail_bar.png The CV/CC indicator is red (Constant Current) while the output is Off.

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

Q10 gw_product_detail_bar.png gw_product_detail_bar.png How to use store and recall operating?

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.


Q11 gw_product_detail_bar.png gw_product_detail_bar.png The output mode of the DC power supply, constant voltage mode (CV mode) and constant current mode (CC mode)

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

Q12 gw_product_detail_bar.png gw_product_detail_bar.png How do I improve the test capacity of programmable power supply?

During the production line test, the programmable DC power supply provides voltage, current, and test time. These three programmable variables enable the automation of complex production line test procedures. However, if you want to further improve the test capacity after automation, you must understand the design and special features of programmable power supply.


First, we need to understand the output characteristics and load effects of the DC power supply.


In order to provide a stable DC output, the DC power supply will have a capacitor at the output to perform the filtering work, and the capacitor does not allow the voltage to change instantaneously, so when you want to change the voltage output, the DC output filter capacitor will make this change a dilemma of application. The smaller the output ripple, the slower the response speed of the voltage change.


The output voltage should become larger: fast when no load, slow when loaded. Life scenario: A car full of passengers and an empty car climb a hill. Under the same throttle condition, the empty car climbs quickly, and the fully loaded car climbs slowly.


The output voltage should be smaller: slow when no load, fast when loaded. Life scenario: a car full of passengers and an empty car go downhill. When the accelerator is not stepped on, the empty car goes downhill slowly, and the full load goes downhill fast. When the power supply provides the function of the bleeder resistor, the voltage reduction time can be increased through the bleeder resistor.


If you need the power supply to perform rapid voltage changes (100u sec level), you can use the DC mode of the AC power supply, such as GW Instek ASR-2000 series, ASR-3000 series AC/DC dual-purpose power supplies.


If a rapid change in current is required, an electronic load can be used to extract the load, forcing the power supply to provide fast current.


In addition to the above issues, the setting time of the hardware and the computer control interface (GPIB, RS-232, USB, LAN) adopted will affect the time of the programmable voltage change.


Application Keywords: Rise Time, Fall Time