After modifying the Corometrics Nautilus Ultrasound cable (TFCU-CM03-0101) to break out pens 3, 4, and 5 as shown in table 5-9 below. This cable was modified such that the ultrasound cable would plug into the core metrics fetal monitor and the breakout end of the cable would connect to the isolation amplifier ISO-Z Head-Stage (Part No. 10-02020).

When this modified cable was connected to the ultrasound the unit functioned as expected. However, once the isolation amplifier was connected it would induce a 150 to 200 bpm signal on the fetal ECG without any stimulation on the actual ultrasound.

Any ideas how to remove this artifact? (cost efficiently)