Glossary Reference Electrode Half cell of the electrochemical cell that supplies a stable voltage that is known, constant and completely insensitive to the measurement solution. Changes in voltages generated from the pH sensor are measured versus this electrode’s voltage. Refractive Index Refractive Index is defined as the ratio of the speed of light in empty space to the speed of light in the substance. Repeatability Repeatability expresses the precision under the same operating conditions over a short interval of time. Repeatability is also termed intra-assay precision. Reproducibility Reproducibility expresses the precision between laboratories collaborative studies, (usually applied to standardization of methodology). Resistivity Electrical resistivity (also known as specific electrical resistance) is a measure indicating how strongly a material opposes the flow of electric current. A low resistivity indicates a material that readily allows the movement of electrons. The SI unit for electrical resistivity is the ohm meter. RH Relative humidity is expressed as the ratio of the quantity of water vapor present in the air to the quantity at which the air would reach saturation (100%) at a given temperature. Robustness The robustness of an analytical procedure is a measure of its capacity to remain unaffected by small, but deliberate variations in method parameters and provides an indication of its reliability during normal usage. rpm Revolutions per minute. RS Reducing Sugars. RS232 In telecommunications, RS-232 (Recommended Standard 232) is traditional name for a series of standards for serial binary singleended data and control signals. RS485 In telecommunications, RS-485 (Recommended Standard 485) is a standard defining the electrical characteristics of drivers and receivers for use in balanced digital multipoint systems. RS-485 can be used effectively over long distances and in electrically noisy environments. S/cm The siemens (S) unit is named after Werner von Siemens, the 19th century German inventor and entrepreneur in the area of electrical engineering. Previously to the siemens per meter unit, mho/cm was used to measure conductivity, where the unit “mho” is a reciprocal ohm. The “mho” is “ohm” spelled backwards. Because of the history of conductivity, μmho/cm and mmho/cm is commonly translated to μS/cm and mS/cm because they correspond one-to-one. The unit of measurement commonly used is one millionth of a Siemens per centimeter (micro-Siemens per centimeter or μS/cm). When measuring more concentrated solutions, the units are expressed as milli-Siemens/cm or mS/cm (thousandths of a Siemens). For ease of expression, 1000 μS/cm are equal to 1 mS/cm. Salinity Salinity is a measurement without the unit corresponding to the weight of dissolved salts in seawater. Salinity is calculated from an empirical relationship between the conductivity and the salinity of a seawater sample. Oceanographic Tables and Standards endorsed by UNESCO/SCOR/ICES/IAPSO are used for the calculation. Salinity measurements are performed with no direct temperature correction. The salinity range is calibrated using a standard sea water solution. SAR Sodium Absorbtion Ratio (meq/L). Sensor Check™ Allows users to check electrode status at any time. °SH Soxlet Henkel degrees is determined by titrating a 50 mL sample with 0.1 M sodium hydroxide to a phenolphthalein end point. SHE Standard Hydrogen Electrode. SMART electrode With models that feature our SMART circuitry, an exclusive microchip embedded inside the electrode retains the calibration data and assigns an identity code to the host unit. As soon as the electrode is connected to a pH meter in the SMART series, it is recognized and its characteristics retrieved. The meter then uses the accessed calibration data as a reference for future measurements. Once 16 Glossary 16.14 | www.hannainst.com
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