A temperature oscillation instrument to determine pyroelectric properties of materials at low frequencies: Towards elimination of lock-in methods

Pyroelectric properties of materials can be accurately determined by applying a new digital signal processing method on the discrete sampled data obtained with a temperature oscillation technique. The pyroelectric coefficient is calculated from the component of the generated current 90^∘ out of phase with respect to the sinusoidal temperature wave. The novelty of the proposed approach lies in the signal analysis procedure which implements a simple Fast Fourier transform that filters residual noise through convolution, and calculates the phase difference between the peaks of the temperature and current waves. The new idea requires relatively simple hardware and enables very accurate measurement of the pyroelectric coefficient of materials at ultra low frequencies, 1–250 mHz, without using costly lock-in amplifiers.