Hello, Maz, A lot depends on whether the EIS generator is commercially manufactured (e.g. by Ode, Trem et al) or home made. I personally use a homemade generator with a current limiting rheostat to prevent runaway, and a 3-inch separation of bullion coin electrodes. For such a setup, a multimeter can be quite useful. I use a multimeter to measure the resistance between the electrodes when fresh DW is in the vessel. Then I adjust the current-limiting rheostat to match the inter-electrode resistance. The multimeter can then be used during the electrolysis process to exhibit the brewing rate. With experience, this gives a good indication of the quality of the brew. The multimeter could then be used either as a microammeter (if it has the proper range) in series with the electrolysis cell, or as a voltmeter in parallel with the current-limiting rheostat or the cell electrodes.
The multimeter could also be used to measure conductivity of EIS in a container outside the brewing vessel, if the wetted probes' length and spacing were kept constant. Even then, the reading would be only be relative. That is, ratios of such readings for different EIS batches would have meaning. Single readings would not, unless the probes' geometry were calibrated using a standard conductivity cell technique. This technique is well-known in college courses in Physical Chemistry or Electrochemistry. Commercially made meters such as the Hanna TDS have been pre-calibrated for a fixed-geometry conductivity measurement, and then calibrated for ionic concentration as proportional to the conductivity. A multimeter is definitely a handy tool to keep around for various purposes in making and checking EIS. I get by, however,with just an analog microammeter (no batteries to wear out) and a Hanna TDS. Best regards, Matthew
