Science Buddies: "Ask an Expert"

I have a basic mat question about multimeter readings for the electrolyte test. I'm sure this question has been asked somewhere on this board, but I can't find it. Some of our readings were achieved on the 20m setting (like Vitamin water -- 6.08) and some of our readings were achieved on the 200m setting (like Gatorade -- 42.1). Before I convert those numbers to amps, and then to Siemens do I have to do anything to the numbers to make them consistent between 200m setting and the 20m setting? In other words, would a 6.08 number achieved at a 20m setting be equivalent to a 6.08 number achieved at a 200m setting? Thank you!

Follow-up question. How do I convert a number achieved at a DCA setting to amps. We measured tap water at a "20 DCA" setting and achieved a number of 5.7. I understand that the M setting = milliamps, and the U setting = micro amps. What does the DCA setting equal? And how would we go about converting that to amps? Thanks.

ataub - You might find a small difference in reading current on the 200 mA vs 20 mA scale owing to possible differences in the internal resistance of the meter. The meter measures current by actually reading the voltage across an internal shunt resistance. But, a reading on a digital multimeter of something close to 6.08 on either scale would be expected. I think the '20 DCA' scale you are referring to is actually '20m' or 20 milliamps in the general DC amperes scale range, just as the other major headings are DCV, ACV and Ω (ohmmeter ranges).

You should be able to take the digits you are reading and make your conversions to Siemens units on conductivity.

Rick Marz

Thank you!