Abstract: A diode-less peak detector comprises first and second comparators (U1, U2) for comparing an input signal (V) with a peak signal. The first comparator (U1) is connected such that the peak signal functions as a reference and the second comparator (U2) is connected such that the input signal functions as a reference. An inverter (U4) is provided for inverting the output of one of the first and second comparators. Means, such as an AND gate (U3) is provided responsive to the output of the inverter and the other of the first and second comparators so as to provide a switching signal. A MOSFET (Q1) is provided responsive to the switching signal and adapted to adjust the magnitude of the peak signal towards the magnitude of the input signal only when the magnitude of the input signal is greater than the magnitude of the peak signal.

Abstract: A liquid particle counter includes an in situ light obscuration sensor (3). The sensor includes a sample cell (1) in the form of a glass tube of substantially circular cross-section for the passage of liquid, a light source (5) for directing a beam of light through the sample cell, and a photo-detector (7) for providing a signal representative of the amount of light passing through the sample cell (1). The signal is processed so as to produce an output (17) representative of a particle count.