Before revision: Care must also be taken to ensure there are no unexpected paths by which leakage current may be encountered as this will defeat the system, and extra care must be taken in the design of the amplifier/buffer circuit to prevent oscillation as the guard, especially if it is used over a coaxial cable, may have a strong capacitve coupling to the input.
After revision: Care must also be taken to ensure there are no unexpected paths by which leakage current may be encountered as this will defeat the system, and extra care must be taken in the design of the amplifier/buffer circuit to prevent oscillation as the guard, especially if it is used over a coaxial cable, may have a strong capacitive coupling to the input.