That depends on if each real world instrument can both source and sink current like their ideal, mathematical, on-paper counterparts. This info may be hard to get.
Some setups may work as long as there is a load but will go crazy when there is no load. Also, some power supplies may not start up properly if they are looking at weird loads.
Why not just use a voltage supply with adjustable current limiting? Or, if you can come up with an equivalent circuit for your load it should be easy to find some way to power that load. If there is a negative resistance region, like in an arc, this could get messy.
You can use interpolation on a graph of the voltages and currents to come up with whatever precision you need.
BTW, two "D" cells in series with a diode will give you 2 to 2.3 vdc and you can put a resistor in series with this voltage supply. One D cell will give you ~1.5 vdc.
Make some V and I measurements on the load with different resistor values and we'll go from there. Start with a 2 ohm, 2 W resistor. It may get hot to the touch.
Last edited by Thatguy; 10-10-2010 at 06:55 PM.
I would go for the voltage supply. What is the range of adjustment on it?
From the data that you gave earlier, it looks like the previous experiment used fixed voltages (1.8, 1.9, 2.0v, etc.) and the current/current density was measured. If for some reason the current was too high and you needed to limit it, you could use a voltage supply thta had a built-in current limiting or you could add a resistor to limit the current.
The way that I see it, the experiment would go like this:
1. Set the voltage (maybe 10 steps changing 0.1v at a time)
2. Measure current
3. Divide current by the area of the electrodes to determine current density
4. Measure reaction efficiency
This is what I understand that you are trying to do. If this is not correct, you should give us detailed information on exactly what you want to measure and how you plan to do it. The more information that you give us, the better we can help.
here is the whole conditions i will work at it , i took it as prtscn to you
some symbols like
- C/M is molar concentration and it equals the no of moles of substances per liter of solution .
- C carbon (graphite electrode).
- pt platintium electrode.
i think you know the rest better than me
i forgot to say that the key condition in this test are :
- electrode type
- current density
That helps a bit. Now the question is: What are you looking to do?
1. Repeat this experiment and see if you get the same results (1.7, 1.8, 1.9v, etc.)?
2. Are you looking to improve these results (finer adjustments between 1.8 and 2.0v and find the best conditions, perhaps using 0.02v steps)?
3. Have you determined how you will measure the current efficiency?
Ideally, you would want the voltage to bounce around less that say 10% of your resolution. So if you were using 0.1v steps (like in the table above), you would want the voltage stable to 0.01v or better (meaning if you wanted 1.8v, the actual voltage might bounce between 1.79v and 1.81v... less variation would be better). Now if you wanted 0.01v steps to improve on that table, the voltage should be stable to 0.001v or better. The other thing to consider is voltage drift. If these experiments take some time, the voltage might change while doing the experiment (depends on your voltage supply). So if the voltage supply isn't properly designed to compensate for this, you might start the experiment with the correct voltage, but the voltage might be different towards the end of the experiment.
So, this is why I ask what you are trying to exactly do (what are your goals?). Finer adjustments require a better voltage source as well as better equipment to measure the fine voltage/current changes.
Do you have the information on that voltage source from your electrical department? You could post the brand and model number and I could see if I could find the specs online for it.
what happened nukeman
is that mean that i must work on the previous circuit
Sorry. I didn't see that you had responded to this before.
Let us know what the electronics department has for a voltage source. You can get the name/model of it if you don't know any more info than that. We can then look up the specs online and see if it will work.
I think he is really from Iran and is finalizing the nuclear bomb detonator details. Call Homeland security!