An improved microelectrode resistance meter

A device is described for measuring the resistance of micropipette electrodes. The useful range of electrode resistances that it can measure is 100 k omega to 1 G omega. It is more convenient to use than previously described or commercially available meters, especially for very high-resistance electrodes. Resistance of even the finest microelectrodes can be measured accurately while their tips are inserted by hand into a test solution. This eliminates the need for special holders, speeding and simplifying the screening of large numbers of electrodes. Test solutions are stored in interchangeable reservoirs, making it easy to characterize the resistance of an electrode in solutions of different resistivity. Test solutions can also be capped and removed when not in use to prevent evaporation. To protect very high-resistance electrodes from damage during measurement, the measuring current is low (only 300 pA on the highest resistance range) and the test voltage across the electrode is limited to +/- 1 V.