Science Buddies: "Ask an Expert"

Hello everyone. Recently, I started working on the Electrolyte challenge for my science fair project. I hooked everything up, made sure my battery was full, fuse not blown, etc. But I found two problems. My first problem was the fact that my multimeter didn't have DCA, ACV, etc. settings. It had these types of settings:

What kind of setting should I use?
So trying to guess, I used the V with the lines and dashed lines on 200 to test my liquids. When I put it in gatorade, i got something like 8.4. But when I put it in tap water, it was 8.4, salt water, 8.4 and etc. What am I doing wrong?
Also, Note: i used the COM and VΩ
This here is my finished product...

Please help. I have try to fix it many times but I have had no success

JapanHat,

Thank you for your question. In this case, you are using the multimeter to monitor current through the circuit. Your device has a separate plugin for the red wire. It looks like from your 2nd picture that the dial is in the right position to measure DCA and your circuit is correct. Leave the black wire plugged into COM but move the red wire from the hole on the right to the one just to the left, mA. You have it set to measure voltage and resistance vs. current. Let us know if this fixes your issues.

I had to research for a while now, ask help from my teachers, and I see why it has to go into the mA hole. But when I tried putting this in any liquids, closing the circuit, all I got was 00.0. I checked all my circuits and it was fine, but I don't know what I'm doing wrong now.

Also, thank you for your reply!

JapanHat,

Given the info you've provided, my money is on something wrong with the Digital Multimeter (DMM). When a DMM reads 0 all of the time regardless of configuration or item it is measuring, it often points to a blown fuse. Refer to your DMM owners manual to find out how to locate and check the fuse. If it is blown, you can usually buy replacement fuses at your local hardware store for just a few $$. If you have access to another DMM, you could verify your readings that way. You could also check to make sure the battery in you DMM isn't dead, but this usually results in your device not even powering on. However, before you start digging into the guts of the DMM, you could check (if not done already) the freshness of your 9V battery in your circuit. You might just change all batteries for known fresh ones, just to be sure. It needs to be as fresh as possible to generate readable results. The current generated by this circuit with everything at full strength is still going to be quite small (milli to micro amps). A week battery will not have the power to generate a current above the minimum threshold of your DMM.

Please post back and let us know how your troubleshooting is progressing.

theborg wrote: snip.

It worked! Thank you soo much!!! After many weeks of frustration, we finally got it to work! Thank you!

So we changed several things on our circuit. First, we switched multimeters. Then we tried connecting it again with the red wire in the 10A hole and the black wire in the regular COM hole. After we connected everything, it for some reason didn't work. We were confused for a while, but after some research, I found out that electrolytes are substances dissolved in water that conducts electricity. Then I saw several videos on researchers using somewhat of the same circuit as ours, except instead of a multimeter, they used a lightbulb. I thought that I could replace the lightbulb, so I made the same circuit, attached it to the multimeter, and got better results! When I dipped my conductance sensor in distilled water, I got .00. Inside tap water, I got the reading, .01. And in Orange Juice, I got .05!

Thank you for helping us get our problem solved and ready for our Science Fair!

So glad it worked out. Good luck with your science fair.

I was wondering if I could put your name in References and Acknowledgments. You have helped me a lot and I would like to thank you for that.

JapanHat,

Thank you for the consideration. I'm really glad you found this forum so helpful. I am honored and humbled that you would like to acknowledge the help you received. If you wish, you can put David B. or you can use my alias "theborg".

However, the support you received in my posts go deeper than just me. It represents not only my own knowledge and experience, but research I've done into other products and posts located within the Science Buddies forum that other SB experts have contributed to as well.

If you wish to acknowledge and reference the help you received, can I suggest thanking the Science Buddies organization/forum as a whole? This would be fitting and help key others into the existence of this wonderful resource for science, technology, engineering, and math.

theborg wrote:JapanHat,

Thank you for the consideration. I'm really glad you found this forum so helpful. I am honored and humbled that you would like to acknowledge the help you received. If you wish, you can put David B. or you can use my alias "theborg".

However, the support you received in my posts go deeper than just me. It represents not only my own knowledge and experience, but research I've done into other products and posts located within the Science Buddies forum that other SB experts have contributed to as well.

If you wish to acknowledge and reference the help you received, can I suggest thanking the Science Buddies organization/forum as a whole? This would be fitting and help key others into the existence of this wonderful resource for science, technology, engineering, and math.

Ok thank you and I will reference Science Buddies also! Thank you for helping us with our project!