Question

What is the CMRR of Foetal electrocardiogram?

(a) 0-150 dB

(b) 0- 130 dB

(c) 0-120 dB

(d) 0-200 dB

The question was posed to me during an interview.

The origin of the question is Ambulatory Monitoring Instruments topic in chapter Arrhythmia and Ambulatory Monitoring Instruments of Biomedical Instrumentation

Answer 1

Correct option is (c) 0-120 dB

To explain I would say: Abdominal FECG processing circuit is used for computing foetal heart rate. After proper placement of the electrodes, the signals are amplified in a preamplifier which provides a very high input impedance (100 MW) and high sensitivity and good common mode rejection ratio (up to 120 dB).