This part of IEC 60477 applies to resistors intended as laboratory AC resistors for use over a range of frequencies from DC up to a stated frequency which is not in excess of 1 MHz. Such resistors are hereinafter referred to as "AC resistors".
In addition to satisfying the requirements of IEC 60477, resistors satisfying the requirements of this standard are designed to have a small variation of resistance and a small phase displacement over the stated frequency range.
Because of the uncertainties in AC properties which can result from stray inductances, stray capacitances, eddy currents, dielectric absorption effects and skin effect, the AC resistors to which this standard applies are classified according to their construction (see Annex D), as follows:
a) Two-terminal resistor which each of one terminal both for current and potential;
b) Three-terminal resistor which has one more shield terminal (also could be called as guard terminal) connected to the electric screen than the two-terminal resistor to reduce the stray capacitances effect;
c) Four-terminal resistor which has independent current terminals and potential terminals to reduce the stray inductances and contact resistances;
d) Five-terminal resistor which has one more shield terminal than the four-terminal resistor;
e) Four-terminal coaxial resistor which has two terminal-pairs with the outer shield conductors working as the low terminal of current or potential;
f) Two-terminal-pair resistor which has two terminal-pairs with the outer shield conductors working as the return path for the signal current (not grounded);
g) Four-terminal-pair resistor which has four terminal-pairs with the outer shield conductors working as the return path for the signal current (not grounded) to eliminate the effect of mutual coupling between the current and potential leads.