Science Buddies: "Ask an Expert"

Electrolyte Challenge: Im doing this electrolytes project and I'm really confused. I have a digital Multi-Meter and i will be testing Gatorade, Powerade , Smart Water, Coconut water, Lemonade, Monster Energy, and Red Bull . My multi-meter has a internal battery do i still need to hook to an external 9volt like shown it the picture on Sciencebuddies??? What are the settings I need to use on the multi-meter to do my testing?? Please explain in detail My mom and I are really confused! We have no idea how to use a multi-meter! and once i get the reading on the meter how do i figure out the electrolytes??? where do i get the numbers to put into G = I /V formula
G is conductance, measured in siemens. === ??? where do i find this #??
I is current, measured in amperes (amp). = # on the meter??
V is the voltage, measured in volts (V). = 9 for 9volt???
Please show me example!!! I thought this would be fun but im now so confused please My mom is also is too confused and of course it is too late to change projects. I have to start my testing now and i only have 2 weeks ( due Oct 27 2011) before i have turn in my findings !!
Thank You!!

[Administator's note: URL for Project Idea: https://www.sciencebuddies.org/science- ... l?from=AAE]

I personally would first try a simpler circuit and approach. Disconnect the leads from you multi-meter and everything else, put your multi-meter on its highest resistance scale, read your meter's manul if necessary to figure out where to plug in the test leads to measure resistance. With the leads not touching anything else, the resistance should measure infinite. Touch (short) the leads together, the resistance should measure zero. If that worked, you have correctly gotten the meter to measure resistance. Next disconnect your current probe from everything. Connect one meter test lead to each end of the current probe. With the probe out of the liquid, it should measure infinite. Put the conductance probe into the liquid to be tested. Write down the meter reading and units (ohms, Kohms, Mohms). The reciprical of ohms is siemens (if you are a scientist after 1881 and accepted the unit standardization) or "mhos" if you are an engineer that finds it easier to just reverse "ohm" and be "old school" about it!

You then have to normalize this conductance to the distance between contacts on the probe. There should be a step in the proceedure on how to do that part.

If you get some ohms, Kohms, Mohms reading and still can't figure out the conversion, post them and be sure to include the units and we can show you how to do the math.

As suggested by Craig_Bridge, you seem to need a bit of background to understand what is going on in the Electrolyte Challenge experiment.
Your multimeter operates in several different modes. First, you need to figure out how to use it. If you have an operator's manual, look it over until you understand how to set it to each mode. If you don't understand the relationship of voltage, current, resistance and conductivity, try finding some beginner's electricity discussions on the web.
After you get the basics down, you should understand that you can measure the conductivity using the internal battery and the meter in the resistance mode, or you can use the external battery with the meter in the current-measuring mode.
For an example, if you used an external 9v. battery as shown in the Electrolyte Challenge discussion and you measured 1 mA. current, the conductivity would be G=I/V = 1 mA/9V = 0.001A/9V = 0.000111 siemens.