Method for circuit fault detection in differential signal detectors

In an electrical circuit that detects differential mode signals in an environment where differential mode signals potentially co-exist with common mode signals wherein said circuit comprising,

• first and second input leads through which both common mode and differential mode signals are input from at least one signal source,
• a differential amplifier block having at least an output lead, an inverting node and a non-inverting node connected to said first and second input leads respectively, said amplifier block having a substantial differential gain of one and such that the signal from said output lead is input into said non-inverting node,
• a potential reference,
• a voltage source connected to said potential reference and to said inverting node of said amplifier block,
• an input lead resistor connected to one of said input leads and its corresponding amplifier block node,
• a method for continuous fault detection in said electrical circuit while detecting signals from a patient, the steps of said method comprising:
• a) attaching the first and second input leads to the patient;
• b) inputting a known voltage signal from said voltage source into the inverting node of the amplifier block;
• c) monitoring the voltage signal on the output lead of the amplifier block;
• and
• d) determining if fault conditions exist in the circuit based on the voltage signal received at the output lead.