terminal 68 the capacitor 66 serves to convert the inverted output signal from inverter 64 from a square wave into a precise spike wave form of positive voltage resistor 70 electrically connected with conductor 52 of regulator 50 insures that the spike wave from the capacitor 66 has a sufficient voltage magnitude at input 68 to actuate the linear integrated timer 72 the linear integrated sequential timer 72 is well known to those skilled in the art and preferably a commercially available model no 556 also manufactured by and available from signetics corporation of sunnyvale california and connected in the manner illustrated at page 6 82 of that company 39 s applications manual is used the timer 72 delays the signal for a period of approximately 1 1 milliseconds after receiving the input signal before producing an output signal of approximately 0 11 milliseconds for synchronizing the sampling of the reference electrode when the impressed current is not present the output signal of the linear timer 72 is communicated through the conduit 74 and another inverter 76 into the electronic switch means 24 preferably a model dg 111 mos fet driver switch manufactured by intersil company of sunnyvale calif and disclosed.