The resistance of a very thin conductor is constant across a particular frequency band and can be measured to be within 10 percent of the direct current resistance. The level of resistance changes in a sample with its dimensions in the well known direct current linear manner. Accepted theory indicates that the high frequency impedance Z should be 40 percent higher than the direct resistance R, i.e. Z.about. .sqroot. .pi. f.mu..rho. + .pi.f.mu. .rho., R.about..sqroot..pi.f.mu..rho. .thrfore.Z.about.1.4 R. However, theory supports that for very thin conductors, the resistance does not change with frequency (i.e., R.sub.metal is not proportional to .sqroot..mu.f ). It can then be concluded that Z.sub.metal = R.sub.metal = a constant up to the calculated frequency limit at which point the metal ceases to be classifiable as "very thin". Consequently, a calibration device is presented here which has a constant value of resistance (identical to impedance) from direct current up to a calculated ffequency at which point the device ceases to be a calibration device due to an expected increase in its impedance. The device's usefulness as a constant impedance for calibration purposes is novel and applicable to the new test methods resulting from recent atomic weapon effects criteria in military uses.