BI-8700 pages

BI-870 Dielectric Constant Meter With Brookhaven's BI-870, measurement of dielectric constants has never been so easy. Simply insert the probe in the liquid to be measured, adjust the two controls on the front panel and read the dielectric constant from the display. The BI-870 can accurately measure in low and high dielectric solvents, including mixtures. Mixtures While literature values of dielectric constants are suitable when using pure liquids, for mixtures of liquids, values are not readily available. Also no simple equation describes mixtures using pure component values. Good zeta potential determinations of suspended colloidal particles depend on the accuracy of the dielectric constant of the liquid. Depending on the particle of interest, a number of different liquids may be used, including mixtures of various proportions creating the need for an accurate measurement of dielectric constant. Theory of Opration The BI-870 has two ranges: 1 - 20 and 1 - 200. Absolute accuracy is ± 2%; repeatability and linearity are better than 0.2%. The measurement signal applied to the outer cylinder of the probe is a low-distortion sine wave a a frequency of 10 kHz. The amplitude is approximately 7 volts rms on the 1 - 20 range and 0.7 volts on the 1 - 200 range. The frequency is crystal-controlled and is, therefore, stable to approximately 1 part in 105. The dielectric constant of the liquid sample is determined by measuring the current between the outer and inner cylinders of the probe. With a stable voltage source and precisely known probe parameters, it is possible to display the dielectric constant directly. Calibration is simple using the back panel adjustment with a liquid of known dielectric constant. Features at a Glance Absolute accuracy to ± 2% Fast & easy to use Compact size Rugged & reliable Easy to clean The probe has an open structure and is easy to clean. It is constructed from two precision cylinders, machined from type 316 stainless steel. Six Teflon balls maintain the cylinder spacing. If the probe is used primarily with low-dielectric constant hydrocarbon fluids, we recommend cleaning by agitation in acetone or ethyl alcohol, followed by gentle drying with clean compressed air. It is important that the probe be cleaned before any residue dries on the cylinders. Since the probe is made of stainless steel and Teflon, it may be cleaned in almost any solvent.