OK, here's the felt tip pen reference electrode and the silver electrode with the bridge. The left glass contains a 100 ml 0.1M KNO3 and the right one contains 100 ml 0.1M KBr. The bridge contains a 0.1M KNO3 solution gelled with ky.


The other photo is the meter setup with a high impedance interface buffer box attached. The interface is battery powered and uses a very high input impedance AD824 opamp as a unity gain buffer. The buffer box is not needed, however, as I get the same reading with and without it.


My initial reading is -74.8 mV. From an old post I found here, the reading should be around -51 mV. The reading stays rock-steady. Earlier, I tried the 0.17M KBr solution used for plating the silver electrode and that gave a reading of -96.5 mV. So possibly I will need a POT to calibrate or find the source of the error in the reading.

-- Jason