• Current shunt according to EN 61000-4-19 (Draft), Annex C, Fig. 3
• External isolating transformers required

IEC/EN 61000-4-19 defines a structure for testing energy meters in Appendix C. Only one decoupling impedance Zdiff is defined, which both assumes a decoupling function and serves as a shunt for current measurement. The disadvantage of this simple solution is the lack of galvanic isolation between the amplifier and the EUT circuit, which is why external isolating transformers must be used for test voltage and current supply.