This bridge will measure inductances from about 1 to 30 at a test frequency of 5 mHz. A 365-pF AM-type tuning capacitor
is used as a variable element. The circuit should be constructed in a metal enclosure. Calibration can be done on known inductors or by plotting a curve of the capacitance of the 365-pF capacitor versus rotation and calculating the inductance from this. The range of measurement can be charged by using a different frequency crystal and/or variation of L2 and C6.