Abstract: A gas sampler (1) for a portable gas analyser, having a cooler or chiller (8) through which cooler or chiller (8) the gas sample is passed prior to being conveyed to a gas analyser, has the cooler or chiller (8) operable by means other than electrical power. The invention also includes a portable gas analyser provided with such a sampler (1).

Abstract: A multiple electrode conductivity sensor generates an output to be applied to a special temperature compensation system that responds to a temperature sensor signal indicative of the sample water temperature. The temperature signal selectively operates a memory unit that contains separate water and salt correction values to be used in adjusting the measured conductivity output. The water correction value represents the conductivity of absolutely pure water at the measured temperature, and this value can be subtracted from the measured total conductivity to produce a conductivity value attributable only to salt impurities. The salt correction signal from the memory unit is then used to scale the measured salt conductivity signal at the standard reference temperature of 25.degree. C., thereby achieving a corrected salt conductivity measurement that can be added to a fixed pure water correction signal representative of the conductivity of pure water at that temperature.

Abstract: In a four electrode conductivity sensor, each pair of electrodes is coupled to a respective one of two operational amplifier circuits that establish a fixed potential relationship between the two potential electrodes so that current flow between the two current electrodes is maintained directly proportional to the conductivity of the solution. Specifically a direct or alternating excitation voltage is applied to the positive input of one operational amplifier, while the other receives a fixed reference potential input. The operational amplifiers supply a unity gain, noninverted output to the respective current carrying electrodes, while the potential electrodes are directly connected to the feedback input of the respective amplifier.

Abstract: An electrochemical reference cell has a reference electrode disposed at one end of a rigid hollow cylinder immersed in an electrolyte solution of known concentration. Different interlocking series of plugs, consisting of a material such as wood, with semipermeable, longitudinally extending capillaries, are fitted together in abutting relation to fill the hollow interior of the cylinder between the reference cell and the other end with one series longitudinally overlapping the other. The abutting end surfaces of adjacent plugs in each series are sealed to close off the capillary path between successive plugs, whereas the outer surface of the last plug in at least one series is left unsealed to be in contact with the test solution, so that circuitious ion transfer path is established between the reference cell and the test solution that passes tranversely through the longitudinal semipermeable capillary walls from the plugs in one series through adjacent plugs in the other.

Abstract: An electrochemical reference cell has a reference electrode disposed at one end of a rigid hollow cylinder immersed in an electrolyte solution of known concentration. Different interlocking series of plugs, consisting of a material such as wood, with semipermeable, longitudinally extending capillaries, are fitted together in abutting relation to fill the hollow interior of the cylinder between the reference cell and the other end with one series longitudinally overlapping the other. The abutting end surfaces of adjacent plugs in each series are sealed to close off the capillary path between successive plugs, whereas the outer surface of the last plug in at least one series is left unsealed to be in contact with the test solution, so that circuitious ion transfer path is established between the reference cell and the test solution that passes tranversely through the longitudinal semipermeable capillary walls from the plugs in one series through adjacent plugs in the other.