Electrolyte Challenge

[saylespk]

The goal of this project was to determine, which of these 3 sports drinks (Vitamin Water, PowerAde, and Gatorade) supplied the most electrolytes versus chocolate milk. For this experiment I used a multi-meter that was used for measuring electrolytes in each drink. The control was distilled water. I performed three controlled tests on each solution. Unfortunately, I'm getting the same reading for ALL: 9.6

1) Cut two pieces of copper wire (6 inches long).
2) Use the princess frog (rubber) as the sensor.
3) Wrapped one piece of copper wire several times around the one of the leg (like you are winding a yo-yo). Leave about 2 inches unwound
4) Did step 3 again on the other side of the leg and ensured the two pieces of copper wire don't touch.
5) Connected the battery to the battery clip.
6) Took the positive end of the multi-meter and connect it to the positive terminal of the battery with an alligator clip.
7) Took one of the copper wires (sensor -princess frog and wrapped with copper wire), attach an alligator clip to it and the other end of the alligator clip and connected to the negative terminal of the battery.
Took the negative end of the multi-meter and connect it to the sensor (other princess frog) with an alligator clip.
9) The sensor (princess frog) was submersed in the drink sample and the results were recorded for each trial.

And as I stated, still getting a reading of all drinks of 9.6.

PLEASE HELP!!!

[rmarz]

saylespk - This question was posted in two different locations. I responded to one, but in case you didn't see it, here was my input. RM

After diagramming your connections, they all seem to be correct. Usually this experiment uses a sensor made of an insulating plastic rod with the two windings. I don't know what your rubber "princess frog" is, but even if it appears to be rubber (usually an insulator) it might, in fact, be conductive. Make sure by using a high range on the ohmmeter scale of your multimeter to verify that there is no measurable resistance between the copper windings on the two frog legs. My second thought, if the frog is indeed a non-conductor, is to question how your meter range has been selected. It should be in the DCA (direct current amperes) and set to the 200 milliampere range. The negative, or black lead in the COM jack, and the positive (red) lead in the VΩM socket. There also have been some reports on this experiment that some students found that the protective fuse in their multimeter had been blown. Another item to check. Good luck.

Rick Marz

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I have also been struggling with this same experiment. I thought we had the correct connections-but after 2 normal readings for distilled and tap water, the multimeter keeps reading zero, even though I am using DCA in the correct range of 2mA and 20mA. I changed my conductance sensor to a tube that seemed to be rubber and checked the probes. I opened the back of the multimeter and the fuse seems fine. Is there somewhere with a picture of the hookups? The original picture is not very clear. My 9V battery is fine. I have spent hours re-doing. Please any advice. Cathy


After diagramming your connections, they all seem to be correct. Usually this experiment uses a sensor made of an insulating plastic rod with the two windings. I don't know what your rubber "princess frog" is, but even if it appears to be rubber (usually an insulator) it might, in fact, be conductive. Make sure by using a high range on the ohmmeter scale of your multimeter to verify that there is no measurable resistance between the copper windings on the two frog legs. My second thought, if the frog is indeed a non-conductor, is to question how your meter range has been selected. It should be in the DCA (direct current amperes) and set to the 200 milliampere range. The negative, or black lead in the COM jack, and the positive (red) lead in the VΩM socket. There also have been some reports on this experiment that some students found that the protective fuse in their multimeter had been blown. Another item to check. Good luck.

Rick Marz[/quote]

[deleted-71882]

To all Electrolyte Challenge experimenters,

There seems to be many unhappy experimenters doing the Electrolyte Challenge. Here are two pictures of the experimental setup that may be useful.


Figure 1: An example of the setup described in Figure 2 of Electrolyte Challenge. Note that the meter is set to "DC ma" and registers 0.00 ma because the sensor is in air. The sensor is made using copper wire wound on a piece of a plastic pencil barrel. I put a very small drop of "super glue" on each winding to hold it on the barrel securely. My copper wire has a tin coating, so it is silver colored. Bare copper works just the same. The clips are used simply to hold the connections together. Any sort of clip is okay. The rubber bands around the test wires are just to keep them out of the way.


Figure 2: The sensor has been placed in a sample of my tap water. Note that the meter now reads 5.75 ma because my water has electrolytes in it just like commercial drinks have, only it's cheaper

Be sure that the wire you use has no insulation on it. "Magnet wire" may look like bare copper , but it isn't bare.

[okl123]

im kinda freaking out bc my report is due on monday and i am getting weird results. I am testing water, milk, diet cokem, gatorade, and orange juice and i set the multimeter on the 200mA range. I am getting answers like .1, .5, and .6! Is this rigt? and how to i figure out the electrolyte values from here?

[okl123]

i put the mulltimeteer on a 9V setting and got answers all around 4.5 range, what do i do

[deleted-93346]

i put the multimeter on a 9V setting and got answers all around 4.5 range, what do i do

I do not know if what you did here was with the probe 1) immersed in the electrolyte or 2) out in the air. But in neither case should you be seeing 4.5 V.

For case 1) you should see 9V, because the very large resistance of the multimeter when set to measure voltage prevents any significant current from flowing, and therefore the E=IR voltage drop from the resistance of the probe in the electrolyte will be zero, and the entire battery voltage will appear at the terminals of the voltmeter. If this is what you did, then either your battery is dead, or your meter is broken (not just a blown fuse).

For case 2) the probe in air is an "open" circuit, that is no current can flow through the loop at all. This is the same as having the voltmeter measure the voltage of the air, so you should see 0 volts. If you see 4.5 volts then the most likely explanation is that your meter is broken (not just a blown fuse).

WW -- if you read this, can you think of any other explanations for the 4.5 V readings?

In the message before your last post you said
"I am testing water, milk, diet cokem, gatorade, and orange juice and i set the multimeter on the 200mA range. I am getting answers like .1, .5, and .6! Is this rigt? and how to i figure out the electrolyte values from here?"
When you see such small readings on a multimeter it means you should change to a more sensitive setting, such as the 20mA range. However, as I noted above, it's likely that your battery and/or your multimeter is dead.

Getting a new battery should be pretty easy. Be SURE never to short out the battery, either by connecting the wire leads from the battery terminal cap together, or, even worse, putting the multimeter probes across the battery when the meter is is set to measure mA. The first case will quickly drain your battery, leaving it partially or wholly discharged (symptom: the voltage across the terminals will be less than 9 V; this is possibly what might have happened in case 1) above. The second case will blow the fuse on the multimeter; however the fact that you were getting readings of 4.5 V according to your second posting seems to indicate that your fuse has not blown.

Any chance that you can borrow another multimeter?

I am sorry that you are experiencing such frustrating difficulties. Experimentation is, indeed, challenging. I hope you persist and find out where the problem lies. Please keep in touch. Also, remember that even if you do not get the "right" answer, if you write up what you did, and the various steps you took to trouble-shoot the experiment, you may well get a decent grade. In my undergraduate days, I not infrequently attempted to perform lab experiments that had been "packaged" with instructions and equipment and failed to get reasonable results. By reporting my efforts fully and honestly I always got good grades anyways, unlike some of my fellow students who attempted to "fudge" their results to agree with what they thought they "should" be. Honesty is of the greatest importance in science. Tolerance for frustration is a prerequisite for all experimenters.

Best of luck!

[okl123]

ok thank you sooooooooooo much, i got a new battery and it worked fine

[deleted-93346]

I am happy that your experiment is now working more as you expected. After all your hard work I hope you get a decent grade! Again, best of luck!