Current mode versus voltage mode measurement of signals from pyroelectric sensors

Abstract

Usually, in photothermal experiments using pyroelectric sensors, the instrumental transfer function is cancelled by normalization to reference measurements, regardless of current (C) or voltage (V) mode processing of signals. Nevertheless, there are several advantages when using a current preamplifier, instead of a high-impedance voltage preamplifier. Due to the low input impedance of the former, the capacitance of the sensor (and its temperature dependence), the capacitance of the connection cable, and the loss resistance of the pyroelectric crystal do not influence the signal. Moreover, the whole input circuitry is less prone to electromagnetic pick up through stray capacitances. In (C) mode, the frequency characteristic is linear (with −180° constant phase) up to a rather high frequency, instead of having (in V mode) a 1/f dependence above a certain frequency and a variable phase shift from 0° to −90°.