Science Buddies: "Ask an Expert"

I’m reaching out because we have honestly hit a wall with my son’s science fair project and could really use some guidance on how to move forward without having to scrap everything he has already done. He has spent the past few weeks researching his project, gathering his supplies, and preparing to test the electrolyte levels in different drinks. We have now spent several hours just trying to get the experiment itself to work.

During our first trial, we received no reading on the multimeter. He went back and did additional research and realized that his circuit needed to be open rather than closed, so we made those changes and tried again. Unfortunately, we still received no readings on the multimeter. At that point, we started troubleshooting everything we could think of. We thought perhaps we had blown a fuse or that our multimeter was too old, so my husband went out and purchased a new fuse and an entirely new multimeter. We retested every liquid with both multimeters and still received no results or it was only showing the voltage of the battery. I also watched several videos showing how others successfully set up similar experiments, and we recreated the setup as closely as possible, but neither multimeter showed a reading of the current in the liquid. I am at a loss and have no idea what we’re doing wrong. Any ideas??

Moderator Note: Project: https://www.sciencebuddies.org/science- ... orts-drink

Trouble-shooting FAQ: https://www.sciencebuddies.org/science- ... drink#help

Hi - I am sorry to hear your student is running into a problem with the Electrolyte Challenge circuit. This is one that works well and clearly.

To help an expert here in the forums provide better assistance, can you attach photos that show both the circuit your student has built and the setting you are using on the multimeter.

Seeing those may help us spot what is happening.

Amy
Science Buddies

The settings on the multimeter are really important here, and a different setting is used for different types of liquid.

Since you said this: "We retested every liquid with both multimeters and still received no results or it was only showing the voltage of the battery." -- Make sure you are choosing the setting to measure direct current, NOT voltage (V).


See "Measuring the Conductance" step 2:
For the distilled water, you will use: measure direct current in the 200 μA range

For the drinks, you will use: measure direct current in the 200 mA range (step 7)

Note these are NOT on the "V" section of the multimeter. On the one shown in the photos in the project, they are on the right in the "A" section. Your multimeter may be different.

This image is from Step 7, where you shift the setting to measure sports drinks:
Amy
Science Buddies

The Multimeter Guide may also be a helpful resource: https://www.sciencebuddies.org/science- ... multimeter