Q: My multimeter is giving me negative readouts. What do I do?
A: You should first check to make sure the leads are in the proper terminal (you might be getting a negative reading if your leads have been switched). The positive node of the battery should be attached to the red wire (+) from the multimeter. Otherwise, try switching the channel to see if perhaps the multimeter was on the wrong setting.
Q: Why am I getting a reading of 0 from the multimeter?
A: There are several issues that may result in a reading of 0 from the multimeter:
One or more of your connections could be faulty. Make sure that all wires are attached securely. Double-check all the connections. The following suggestions may help you troubleshoot:
- Your multimeter is not set to a sensitive enough scale. The currents flowing through the liquids in this experiment are very small, so your multimeter must be set at a high sensitivity. A current range of 200uA (microamps) seems to work well for most experiments.
- Your battery might be dead, meaning that the experiment is without power. You can check whether or not your battery still works by putting your multimeter in the 10 volts range and connecting the leads to the battery. If the reading is 9 or above, your battery is still working.
- Your electrode may have become compromised in some way. There should be no material collected on the electrode; if there is anything collected on the electrode, clean and rinse it well and try again.
Q: Why are my readings going up and down?
A: There are two possibilities for why your readings are fluctuating; you can tell what is happening in your experiment by how much the readings are changing. If the fluctuations are very small (i.e., the reading stays around the same number but increases or decreases slightly), you have nothing to worry about. In these types of experiments with multimeters, it can be very difficult to get an entirely stable voltage, and slight fluctuation is normal.
If your measurements are decreasing more quickly, you may have encountered a problem with electrolysis. Electrolysis is when water is broken up into hydrogen and oxygen gas by an electrical current. You can tell if electrolysis is occurring because there will be little gas bubbles of hydrogen and oxygen collecting on the electrode. The electrolysis will cause there to be a smaller surface area on the electrode, and your readings will decrease.
Q: What if I still need help using a multimeter?
A: Science Buddies has a guide to using a multimeter, which can be found here: http://www.sciencebuddies.org/science-fair-projects/project_ideas/Elec_primer-multimeter.shtml?from=AAE
Q: I'm not very familiar with electronics in general. Where can I find help with the basics?
A: This particular project is one of the more challenging electronics projects in the Science Buddies library of Project Ideas. We have a basic electronics primer that is found here:
As always, if you need help, we encourage you to seek assistance from parents or science teachers. In addition, you can try one of our easier electronics projects before beginning with this one, as this one requires you to put together multiple components of a circuit.
Some electronics projects with a lower level of difficulty can be found here:
If you have other questions about the procedure or need assistance troubleshooting your project or the Experimental Procedure, please post your question in the forum for this kit at Ask an Expert: http://www.sciencebuddies.org/science-fair-projects/phpBB3/viewforum.php?f=56. Our team of volunteer Experts is available to assist. We attempt to reply to questions within 24 hours. Please note that you will need a free Ask an Expert account in order to post questions.