A measuring bridge is described which is applicable in the 1 kHz-30 MHz region to the determination of the impedance of biological material and highly conducting liquids characterised by a very high loss factor. The novelty in this bridge is the use, as the resistance standard, of two trimming potentiometers and two small ferrite shielded transformers as the output to the detector. This makes it compact, versatile and free of inductive and capacitive effects.