Electrolytes: Sports Drink vs. Water..etc.

[chicken wings]

After I set up the experiment...by connecting the multimeter to the battery and the copper wire, I have been unable to come up with any readings on the multimeter. So I have 2 questions:

1. What is the correct setting on the multimeter, that will give me the correct results?

2. What should the correct readings look like...will the numbers be in the tenths? .1 hundredths? .01 etc.

Any help is appreciated. I need an answer ASAP because I have to turn this in on Monday.

[rmarz]

chicken wings - The instructions for this experiment suggest some setup procedures. Most inexpensive multimeters have 4 ranges of DC current. 0-200 microamps, 0-2000 microamps (2 milliamps), 0-20 milliamps and 0-200 milliamps. Because of the broad range of conductivity of the liquids you might be testing, you will probably have to change to more than one range. For pure, distilled water for example, you will probably need the most sensitive range of 0-200 microamps (as mentioned in the experiment description). As you test more conductive sports drinks, you may be in the 0-200 milliamp range. As good practice, you will usually start at the higher current range and go lower until you get a reading between 20-80% of the current range that was set. This is a carryover practice from the use of older, analog meters that could be easily damaged when the current being measured exceeded the range that was set. Today, inexpensive digital multimeters are well protected and go into an 'overrange' reading on the display with a modest overload without permanently damaging the instrument.

Rick Marz

[chicken wings]

What I meant was....I've tried all of those settings and I don't get any results, it always shows up as 0, accept for when I measure volts, which i know is just measuring the charge coming out of the battery. So why am I getting 0 amps on every setting (I've tested it on 2 multimeters, so it's not that)? What would be the correct schematic setup, because I've done it the way described in the experiment but that doesn't seem to be working?

[rmarz]

chicken wings - I did a quick experiment using the 9 volt battery, an inexpensive multimeter like the one shown on the diagram, but with a slightly different sensor. I wound two coils of about 4 turns of #22 bare copper wire around a 1/4" plastic rod, the coils about 1" apart. I only tested two liquids, plain tap water which read about 50 microamps, and orange juice, that measured about 300 microamps. I'm sure that a sports drink will exhibit higher conductivity. However, the circuit in the diagram does work. I know the description said that polarity doesn't make a difference when connecting the meter, but I think you should connect the positive (+) battery connection to the positive (red) multimeter lead. This is observing proper polarity. Some meters might not be able to read current as a negative value. The fact that you can read voltage in this setup suggests that you have everything wired in proper series. A caution, do not switch the multimeter through different ranges while the probes are in a liquid. You could possibly pass through sensitive resistance ranges and blow a fuse in the meter or damage the circuitry. If you have access to a resistor of any known value (say above 500 ohms) you can test the setup and the current ranges of the multimeter. A 1,000 ohm resistor in this circuit (replacing the sensor) should read about 9-10 milliamps. Use Ohms law to check your reading. I = E/R, where I is current in amperes, R is resistance in Ohms, and E is the battery voltage in Volts. It is possible that your meter is damaged and that a shunt resistor is burned out or a fuse is blown (not all meters use protective fuses). If your meter test with a resistor checks out you should be good to make measurements per the experiment. Check your battery with the multimeter (on a proper DC voltage range) occasionally to check that is OK.

Rick Marz