Wearable cardioverter defibrillator (wcd) with ecg preamp having active input capacitance balancing

A method, comprising:

• obtaining a plurality of electrocardiogram (ECG) vectors from a plurality of ECG electrodes;
• applying an impedance measurement circuit across a first pair of the ECG electrodes;
• applying a balancing impedance across a second pair of the ECG electrodes;
• and
• obtaining an impedance measurement across the first pair of the ECG electrodes while obtaining the plurality of ECG vectors.

An electrocardiogram (ECG) monitor, comprising:

• a plurality of electrocardiography (ECG) electrodes and an electrode to provide a common reference for the plurality of ECG electrodes;
• a preamplifier coupled to the ECG electrodes and the additional electrode to obtain ECG data from the patient as one or more differential ECG vectors;
• and
• an impedance measurement circuit to measure an impedance across a first pair of ECG electrodes, wherein the impedance measurement circuit is to apply a balancing impedance across a second pair of ECG electrodes when an impedance of the second pair of ECG electrodes is not being measured.