A more precise and cost effective means than previously commercially available for measuring alternating currents up to 100 amperes in the frequency range from direct current to 100 kilohertz can be measured with precision approaching 0.001% employs a shield around a resistive network. The shield is electrically isolated from the resistive network, but acts as a heat sink to draw heat generated by the resistive network away, promoting fast stabilization times. The shield also provides electrical shielding from outside interference allowing the geometric arrangement of elements in the resistive network to minimize induced inductance and capacitance.