I'm a bit embarrassed about this but I just bought a benchtop power supply and I can't figure out how it works.

I should explain that I'm new to electronics and I've never used a benchtop power supply before. The instructions appear to have been translated into English and are somewhat less than clear.

All I want to do is test that the power supply is working. I have attached a multimeter and adjusted the DC voltage and the meter correctly reflects the voltage as expected but when I try to adjust the current, nothing happens. The power supply digital meter remains at 0A as does the multimeter.

The power supply is here: http://www.abra-electronics.com/products/catalog/150-Watt-Benchtop-Power-Supply-p-5266.html and I have attached a PDF of the instruction manual to this post.

Any help would be appreciated.

- Adam

 

Actually you don't adjust the current though a load. The load draws as much current it needs according to its impedance and voltage applied. The only thing the current function makes is to limit the current through the load to a safe value (the value you set it).

Also, you can use it as a current source but you won't be able to adjust the output voltage since it depends on the load.

Read the manual carefully to see how it works.

 

Hello,

Can you make a sharp picture of the front of the power supply ?
This will make the reading of the text on the front more easy.
(on the picture on the website and in the manual the text is unreadable).

Greetings,
Bertus

 

Hi Bertus,

The image is attached.

- Adam

 

If you want to use it a current source set the voltage to maximum and limit the current to the desired limit.

Note that, it won't work as a current source for loads which have higher resistance than the output voltage can supply the set current.

 

Hello,

The Powersupply has two knobs for current and two for voltage.
The current knobs must be set to max and the voltage knobs to minimum before switching on.
Current and voltage have two knobs each, a course and a fine.
With the course knob you can bring the value in range and with the fine you can put it on the exact value.
Current limiting can be used for testing low impedance loads. (as mik3 already told you).

The drawing in the manual does not fit your powersupply.
As far as I can see it is a single power supply.
The load can be connected to the + and - terminals.

Greetings,
Bertus

 

Thanks Bertus and mik3, I appreciate your help and advice.

I understand what's going on now. After reading the manual I was confused, partly because of my inexperience and partly because the manual lost some clarity in translation.

One last question: the manual mentions a 'proper variable load' but gives no details. Does it mean a potentiometer? If so, what sort?

- Adam

 

Hello,

If "the proper variable load" is an potmeter, it must be a very large one.
The powersupply can deliver upto 150 Watts.
I think it is a strange way of telling that the current limiter can be tested this way.
( the CC led will burn if there is to much current through the load and current limiting is active ).

Greeting,
Bertus

 

To test the power supply, which is stated as 5A/30V, you would need a 6Ω high power resistor as load. You can buy several high power resistors and connect them together to get 6Ω. You can place them in water to increase the wattage as they become hot very quickly with 150W of power.

Follows the following steps:

1. set output voltage to 30V and current knob to mid way

2. connect 6Ω load to power supply and note that output voltage will drop as it goes into current limit

3. slowly adjust the current limit until you get 5A on ammeter. note that the output voltage also increase when you adjust the current limit.

4. if the voltage reading does not returning to 30V or 29.9V when you have 5A output current, your power supply is bad

5. if you can't get 5A or 4.99A, the power supply is bad

6. keep current limit setting untouch and remove load

7. set output voltage to zero or lowest

8. short circuit the output

9. adjust output voltage up slowly.

10. if you can't get 5A, the power supply is bad.