KORAD KA3305P Power supply

[rsfoto]

Hi,

This might be a dumb question but anyhow.

I have the above Power supply and want to use negative and positive voltage so I measured my outputs taking the green plug as Ground for the positive and negative voltage. I adjusted the output to 5 Volt and when measuring with my multimeter I do get positive and negative measurements sign but the voltage is not the adjusted one e.g. 5 Volt

So what is wrong. Measuring Red against Black gives me the correct adjusted voltage.

Thanks for any tips or what am I doing wrong ¿?

regards Rainer

[CustomEngineerer]

You don't need to include the ground (green) connection unless you want your circuit to be grounded, which is usually not what you want. Generally to have a positive and negative voltage, you should hook the positive of the first channel directly to the negative of the second channel, this connection is your 0 voltage level, then the negative of the first channel is your negative voltage, and the positive of your second channel is your positive voltage.

[rsfoto]

You don't need to include the ground (green) connection unless you want your circuit to be grounded, which is usually not what you want. Generally to have a positive and negative voltage, you should hook the positive of the first channel directly to the negative of the second channel, this connection is your 0 voltage level, then the negative of the first channel is your negative voltage, and the positive of your second channel is your positive voltage.

Hi,

Thanks a lot. So that means I need to adjust both channels to 5V. ¿ is it possible to use different voltages for positive and negative ?

Again thanks. Will test it right away

regards Rainer

[xani]

Yes it is

You can also switch it to serial mode, just hold the serial button for few seconds. It will:

• Make one channel track another's voltage
• Connect first channel with second internally

So if you need symmetrical +/- voltage it is pretty handy

[CustomEngineerer]

This is a great video on the subject. Highly recommended. Alan uses 2 separate supplies, but it's really no different than if the 2 supplies were in the same case, like in your Korad. Definitely check with your multimeter (and in the user manual for you Korad) if series mode really does connect the outputs of the 2 channels together internally, on some power supplies it does, and on others it just enables the channels to be controlled together and you are expected to connect the 2 channels together externally.

[rsfoto]

Hi,

Parallel to my question here I did send an e-mail to Korad in China. I think it is worth to say that Korad really cares about customer service.

They replied to me today and I was told the Korad KA 3305 P can not deliver positive and negative voltages ... See content of the mail as well as they took the time to send a sketch of how should I connect my wires. That is really after sales customer service. It made my day.

[CustomEngineerer]

Thats correct. Their drawing is exactly what I described doing. Voltage is relative. Look at the picture and think this through. If you hook the common input of a multimeter up to the middle connection, then the positive input of the multimeter up to the negative connection of channel 2 in the drawing, what voltage will your multimeter show? -5V. Try it.

Voltage is just the difference in potential between 2 points. Looking back at the drawing, think through these scenarios (and test them with your meter).

1) Hook the common input of the multimeter to the negative terminal of channel 2. What voltage will it show if you hook the positive input of your multimeter up to the middle connection of the between channel 1 and channel 2? What voltage will it show if you then hook the positive input of the meter up to the positive of channel 1?

2) Hook common input of multimeter to positive terminal of channel 1. What voltage will show if you hook positive input of your meter up to middle connection between channel 1 and channel 2? What voltage will show if you then hook the positive input of the meter up to the negative of channel 2?

3) Hook common input of multimeter to middle terminal between channel 1 and channel 2. What voltage will show if you hook the positive input of your meter up to the positive terminal of channel 1? What voltage will show if you then hook the positive input of the meter up to the negative terminal of channel 2?

Edit: removed poorly worded sentence to prevent confusion.

[rsfoto]

Thats correct. Their drawing is exactly what I described doing. Voltage is relative. Look at the picture and think this through. If you hook the common input of a multimeter up to the middle connection, then the positive input of the multimeter up to the negative connection of channel 2 in the drawing, what voltage will your multimeter show? -5V. Try it.

Voltage is just the difference in potential between 2 points. Looking back at the drawing, think through these scenarios (and test them with your meter).

1) Hook the common input of the multimeter to the negative terminal of channel 2. What voltage will it show if you hook the positive input of your multimeter up to the middle connection of the between channel 1 and channel 2? What voltage will it show if you then hook the positive input of the meter up to the positive of channel 1?

2) Hook common input of multimeter to positive terminal of channel 1. What voltage will show if you hook positive input of your meter up to middle connection between channel 1 and channel 2? What voltage will show if you then hook the positive input of the meter up to the negative of channel 2?

3) Hook common input of multimeter to middle terminal between channel 1 and channel 2. What voltage will show if you hook the positive input of your meter up to the positive terminal of channel 1? What voltage will show if you then hook the positive input of the meter up to the negative terminal of channel 2?

Edit: removed poorly worded sentence to prevent confusion.

Hi,

I tested all 3 scenarios and there was only nonsense readable on the multimeter. Both channels where set up to 5V

Thank you