Abstract: An interdigitated microelectrode (2) comprising a substrate (4), a first layer (6) of a first metal on the substrate (4), and a second layer (8) of a second metal on the substrate (4), the first layer (6) comprising a plurality of line microelectrodes (10) which are connected at a first end (12) and are not connected at a second end (14), the second layer (8) comprising a plurality of line microelectrodes (16) which are connected at a first end (18) and are not connected at a second end (20), the line microelectrodes (10) of the first layer (6) and the line microelectrodes (16) of the second layer (8) being such that they extend into each other but do not touch each other thereby to form an interdigititated microelectrode array (22), and the first metal being different from the second metal. A process for producing the interdigitated microelectrode (2) is also disclosed.

Abstract: A probe or sonde (1) comprising a plurality of sensors (3, 4, 5, 6, 8, 9, 10) for sensing different parameters, at least one sensor being mounted on or at one end of the probe or sonde (1), and at least one sensor being mounted on or at the, or one, side of the probe or sonde (1). The probe or sonde further comprises a centrally positioned stirrer (7) and in constructed from plastics discs bonded together or separated by gaskets. Sensors are used for measuring different water quality parameters, flow and temperature.

Abstract: An apparatus for sensing at least one parameter in a liquid including a sensor means for sensing the parameter, a rotation means and a drive generator means for driving the rotation means as well as to generate electricity passed to an electricity storage means. In addition to a control means for operating the rotation means which also operates in a flow of the liquid and in which the rotation means maintains the flow of liquid at or above a predetermined value.

Abstract: Apparatus (2) for monitoring chlorine in water (4), which apparatus (2) comprises a flow cell (6), the flow cell (6) containing a chlorine sensor (62) and an automatic calibration system, and the automatic calibration system being such that it comprises a small pair of in-line electrodes (50) for generating low concentrations of free chlorine, and injection means (44) for injecting in use of the apparatus a salt solution (64) of known concentration.

Abstract: Apparatus (2) for driving an amperometric electrochemical sensor, which apparatus (2) comprises a microelectrode (30), drive means (36) for the microelectrode, and signal processing means (3), the apparatus (2) being such that the drive means (36) supplies successive pulsed chronoamperometric different conditions to the microelectrode (30), the microelectrode (30) produces a sequence of different voltages consequent upon receiving the chronoamperometric different conditions and correlates the received chronoamperometric different conditions with their respective measurement circuits, and the signal processing means (3) interrogates only the current corresponding to a particular voltage in the sequence of different voltages and thereby produces a single sensor output corresponding to each separate voltage in the sequence of different voltages whereby interrogation of the amperometric electrochemical sensor is facilitated.