Describes an interface device to be inserted into a capacitance spectroscopy characterisation system, between a commercial capacitance meter and a X-Y recorder. This interface samples its input signal using classical electronic components. These samples are processed giving an output proportional to C(t₂)-C(t₁), and whose amplitude varies when the temperature sweeps from 77K to 450K. The rate window extends from 10^-1 s^-1 to 10³ s^-1. The sensitivity for detecting the number of traps is about 1/1000 of the free carrier concentration.