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How to Set Current Limit for a Mastech or Volteq CC CV Power Supply?

Setting the current limit on a Volteq DC power supply is easy.

You simply turn on the power supply without load, turn the current knob counterclockwise until it stops. Short the output terminals (between + and - terminals) with appropriate sized wire, and adjust the current knob to the level you want (you may need to raise the voltage limit if you ran into CV mode). Now  you can reduce the voltage knob settings so that the output goes to zero, and disconnect the short and connect the load of your choice. Turning up the voltage knob high enough will put the power supply in CC mode with the correct current value you set.


Setting the current limit is a little bit more complicated for a Mastech DC power supply, because it comes with short-circuit protection. You should be especially careful if you have one of the following situations:

1) your load has internal source of EMF, this includes battery, DC motors, RC cars and trains, any electrochemical systems including plating, etching, and electrolysis, etc. 

2) your load might be sensitive or damaged by over voltage, e.g., LED

In the first scenario, we stronly recommend that you get a Volteq regulated power supply with over-voltage protection. You will rest assured that the power supply is not going to be damaged by the reverse EMF from your load.


In the second scenario, if you can find a simple load like a power resistor or a halogen lamp that can handle the current you want to pass, you can set the current similar to the first scenario (Caution: the power resistor or lamp might be very hot if you are passing large current). Once you are done with setting the current limit, turn the voltage down to minimum, disconnect your load of resistor or lamp, then connect you actual load. you can now slowly increase the voltage while leaving the current setting unchanged, just remember to always stop before you raise the voltage too high for your load. If your calculation is correct, then you should be able to stop the voltage knob before actually damaging your load.

If you cannot find a power resistor or lamp, you can still set the current limit you want by following the steps below:

Step 1: before connecting your load, set the voltage limit to the maximum level allowed by your load (the power supply should be in CV mode, turn the current knob up if necessary). Now turn the current knob to slightly above minimum position, so the power supply stays in "CV" mode.

Step 2: connect the load; the power supply should change to "CC" mode. Slowly increase the current limit, and you should be able to reach the desired current output if your calculation is correct.

Step 3: when you are done with your test, make sure to reduce the current to minimum position before you disconnect the load. You can now safely switch off the power supply.





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