A photopyroelectric measurement device for liquid investigation and monitoring

A calorimetric measurement device based on the front photopyroelectric (PPE) configuration, consisting in a composite pyroelectric sensor and an irradiation LED, aimed to generate modulated optical excitation is presented. The proposed device is designed for on-field measurements and monitoring of a sample's thermal effusivity, when the investigated liquid is a semi-infinite layer. The composite PPE sensor is in fact a planar multilayered system, developed in order to have a rigid external surface and to allow picking - up the PPE signal by only accessing one side of the ensemble while the other side can be completely submerged in a liquid. The device is meant to be equipped with an internal preamplifier and an internal controlled current source in order to increase its independence and consequently in order to use it as a remote measurement device. A modulation signal conditioner has also been designed in order to provide a control voltage for the current source which drives the LED. The measurement device along with the modulation signal's conditioner, with the current source, and with the preamplifier is intended to be used with any embedded control system, provided with a multichannel analog to digital converter and which can deliver two control analog signals. Emphasis will be laid on describing the signal conditioning chain for the excitation source and the signal conditioning chain for the modulation element.