The amplifier chassis, amplifier output shield, equipment enclosure, and low side of the amplifier output are grounded normally (I.e., they are all connected to the system power-hungry ground). This step serves to ensure personnel safety and stabilize the recording or display system (to which the amplifier provides its output) with respect to system ground. The isolated amplifier input guard shield is then connected to the signal cable shield, a step that extends the amplifier guard shield out along the entire length of the signal cable. (Note once again that the amplifier guard shield is isolated from the amplifier chassis and the measurement instrument enclosure.) Finally, the cable shield is connected to the signal ground point. Care must be take that this is the only point at which the cable shield and the signal ground wire make contact with ground. It was pointed out earlier that the common-mode voltage appearing at the amplifier inputs has essentially the same value as at the signal ground point. Thus, by connecting the guard and cable Shields to the signal ground point, the signal-cable, amplifier-guardshield circuit becomes driven to that common-mode voltage as well. Since the guard shield circuit is thereby kept at essentially the same potential as the low-level signal wires, capacitive coupling of any ground currents flowing in the guard shield to the signal leads will be kept to a minimum