# How to measure resistance of resistance of gel electrolyte using multimeter

How can I measure the resistance of a gel electrolyte using a multimeter? I know the formula to measure the conductivity of a gel electrolyte is k = (1/R) * (d/a)

where k is the conductivity (S/cm), R is the resistance (of the electrolyte), d is the distance between the two electrodes, and a is the effective area of the electrodes.

I wanted to measure the conductivity of the gel electrolyte with just a multimeter. Since this is a gel electrolyte, I was thinking to substitute the thickness of the gel electrolyte as d and substitute the area of the gel electrolyte as a. (I know the area (a) has to be that of the electrodes, but I want to measure the conductivity of the gel electrolyte without the electrodes). So now all that remains is the resistance of the gel electrolyte. To do this can I just measure its resistance using a multimeter?

Thank you.

You would get a number but I'm not sure it would be a good one, due to possible potentials and polarization.

I think you'd be better to use mains or low-audio frequency AC with a series resistor and measure the AC voltage across the electrode vs. the total voltage, then you can easily calculate the AC resistance of the electrode.

simulate this circuit – Schematic created using CircuitLab

Rx = $\frac{\text R_S}{(\frac{\text VM2}{\text VM1} -1)}$

• "then you can easily calculate the AC resistance of the electrode." By his do you mean the resistance of the electrolyte. Like I know that you have to measure the conductivity of an electrolyte using two electrodes (which are the same), but I wanted to measure the resistance of the electrolyte without the electrodes because I don't have an AC source at my disposal. – user5139637 Aug 5 '15 at 15:45
• Do you know how I could make this low audio frequency AC? – user5139637 Aug 5 '15 at 16:03
• You need to connect with it whether you're using AC or DC (as a multimeter uses). Can't you find a function generator or a mains transformer or even use the sound card on your PC? – Spehro Pefhany Aug 5 '15 at 16:06
• Yes, it will work with low audio frequency AC. Limited by the response of your multimeter (check the manual) but a few hundred Hz should be fine. Sound card would work. – Spehro Pefhany Aug 5 '15 at 16:07
• I do not have a function generator or a mains transformer. So as you said, using a dc source as compared to an AC one would give incorrect results? Would the results be really off if I used a dc source or just a multimeter to check the resistively? – user5139637 Aug 5 '15 at 16:12