Science Buddies: "Ask an Expert"

When I did this experiment I did it on an auto ranging multimeter. This way I just set it to direct current. First of all is that the correct setting? When I actually did the experiment, I was unsure what the number that showed up on the multimeter was measured in? Also all the readings were almost the exact same (3.37,3.38,3.36). I tested Gatorade tap water distilled water, orange juice, orange NUUN, and powerade. Although what made me think the results were inaccurate was that the distilled water was around the same as the other drinks? I also thought there would be a significant difference in the different drinks? Please help me figured this out, do I need to convert the number or am I doing it wrong?

Kylie-Brez - The readings are certainly curious. I would think the auto-ranging meter would tell you what the range was that's displayed. It should be set to DC current. That said, its possible that the distilled water is 3 microamps, tap water is 3 milliamps, and the sports drink could be 30 milliamps, not 3? something. Perhaps you could borrow a multimeter that is manually set. What make/model meter are you using? I will try to research that for you.

Rick Marz

Right now I'm using a fluke 73 II series. I tried doing some more research and was wondering if using the 300mA setting would be any more use than the plain direct current one?

Kylie-Brez - I think using a dedicated 300 milliamperes DC range is a good idea. It should give you valid readings for everything except distilled water. You may have to use a range in the microampere range for that measurement.

Rick Marz

Sorry rick I had misread the setting it is actually 300 mv direct current instead of 300ma, are they close to the same?
By the way I tried it anyways and it said ol which I think I read that it meant it wasn't strong enough.

I had redone the experiment and got these results
Distilled water 3.17
Tap water 3.29
Orange powerade 3.36
Orange Gatorade 3.36
Orange juice 3.35
Orange NUUN 3.34
Trying to make it sounds reasonable to other results I've seen, while connecting it to your first answer I converted the numbers

Distilled water I divided it by 10 to get .317
Tap water I left the same 3.29
Orange powerade and the others I multiplied it by ten to get 33.6
Orange Gatorade 33.6
Orange juice 33.5
Orange nuun 33.4. Do these answers sound more reasonable? Did I do the conversions right?
Ps thanks for helping me out!

Kylie-Brez - The question is why did you do the math conversions? Did the meter show what the full scale range was when it was in the measurement mode to give you the basis for the conversions? Although the numbers are in the right general range, I find that the nearly identical numbers for the sports juices probably suggests that you are not getting proper measurements. I haven't been able to download a good instruction manual for this meter, but reviewing what I could find, it has a single current range, just 'A' with the DC symbol (also 'A' with the AC symbol). The DC current full scale ranges are listed as 0-32 milliamps, 0-320 milliamps and 0-10 Amperes. I can't find a picture of what the LCD displays as it autoranges, but it should give you some idea as to which of the current ranges you are on. I have dont this experiment several times and always used a manual multimeter, but found that the differences between several sports drinks, orange juice, cranberry juice and apple juice vary from 30 milliamps to 90 milliamps with the setup shown in the project instructions. I've attached poor photo of this Fluke model The photo shows a dedicated socket for both the 10 Amp range and the 320 milliamp range. You should be using the 320 milliamp range for the RED lead and the COM socket for the BLACK lead.

Rick Marz