Science Buddies: "Ask an Expert"

Hi, I am also trying to do the Electrolyte Challenge and I can't even get the conductance sensor properly hooked up. The instructions are very confusing. Can you clearly explain how to hook it up?

Here are specific questions:

1. Step 6 says attach one of the copper wires to the positive terminal of the 9-V battery using the wire with one of the alligator clips. How do I do this? Do I attach the copper wire to the positive wire of the battery clip or directly to the battery terminal?

And the Figure 2 diagram shows that the positive terminal of the battery is actually attached to the multimeter, not the copper wire of the conductance sensor. Which is correct? If I attach the positive terminal of the battery to the multimeter, do I attach it to the red or black terminal and how do I do that? By attaching the battery clip wire to the probe?

2. Step 7 says to attach the other copper wire from the sensor to the black terminal of the multimeter with the other alligator clip. How do I do this? Do I attach the copper wire to the black terminal's probe with the alligator clip?

And the Figure 2 diagram shows the other copper wire is attached to the negative terminal of the battery, not the multimeter. Which is correct?

If I follow the written directions I end up with the negative lead from the battery and the red terminal of the multimeter with nothing attached. But the Figure 2 diagram shows that both positive and negative battery terminals are hooked up and red and black terminals of the multimeter are hooked up. Please explain!

3. Finally, I'm confused about the multimeter settings. To measure current, I assume I turn the dial to the right side of the multimeter that says "A direct" with the settings of 2000, 20m, 200m and 10A. Is that right? And does 200m mean microamp? It says to use that setting for the distilled water but higher settings for sports drinks...so should I set the dial to 10A?

So far I've tried to put together the circuit with the written directions and the diagram and both times the readings were 0.00 even for sports drinks, which I expected to have some current. So I think I messed up putting the conductance tester together.

PLEASE HELP ASAP - my data is due Tuesday!!!

Thank you,
Elise T.

eliset - There have been several other visitors that have had problems with this experiment setup. If you do a search from this page on 'Electrolyte Challenge' you can read several past posts. The circuit diagram is very simple. The multimeter is connected in series with the battery and the probe assembly that will be immersed in the liquid. While not clear, the (+) terminal of the battery should be connected to the RED or p(+) lead of the meter for correct polarity. You are correct that the meter should be set to read Direct Current (A), and the lowest range shown in the diagram is the 200 microamp setting. That is a good starting setting for distilled water. As you progress to the more ionized sports drinks you will probably be in the 20 or 200 milliamp ranges. Good luck.

Rick Marz

https://www.sciencebuddies.org/science- ... p053.shtml

Do you know about mock up experiment?