Abstract: Methods and apparatus for measuring electrical conductivity particularly but not solely for use in detecting mastitis in individual quarters of a cow's udder employ the cyclical charge and discharge of a capacitor (C1) through liquid in a conductivity cell (9), the cycle reversing on the potential applied to the capacitor (C1) reading a high reference potential and a low reference potential by applying the reference potentials to terminals (10,15) or sensing leads (32,33) of electronic devices (VC1, VC2) or (31) to cause operation of switches (SW1SW2) or (S1, S2) so that the variations in frequency are indications of conductivity of the cell (9). In one modification a reference conductance (30) is included in the circuit during charging of the capacitor (31) and the rate of the time periods of the cycle gives an indication of the conductance of the cell (9) in terms of the reference conductance (30).

Abstract: An electrical conductivity indicator has a bridge circuit which is supplied from a source of electronic oscillations preferably successive half cycles being of reverse polarity and having electrodes in a cup arranged to be hand held below the teat of a cow so that the presence or absense of Mastitis infection is indicated by the variations in electrical conductivity of the milk held in the cup.