Development of a Small In-Situ Conductivity Instrument

Abstract

The instrument was originally developed by the Applied Physics Laboratory, University of Washing-The initial development and testing of a small ton,+ and is now commercially available from Seain-situ conductivity instrument was reported at Bird Electronics (under license from the University OCEAN 73.l Since then, extensive operational ex-of Washington) as Model SBE-4 ( Figure 1).perience has been obtained with a number of these instruments an moorings and on free and tethered ~ ~~~ ~~ . = ~~ ~ ~ ~ platforms that move vertically and horizontally. ~~~~

Current observations in Buzzards Bay, Massachusetts, 1982-1986; data report

“…The transmission sensor voltage was measured for about 0.1 sec in the center of the VACM sampling interval. Conductivity was measured by means of a Sea Bird Inc. conductivity sensor (Peterson and Gregg, 1979). Output of the sensor was averaged for 1.875 sec in the center of the VACM sampling interval.…”

The Effect of Pseudofrazil Particle Entrainment on Salinity Measurements

“…SBE build standard CTD instruments which produce measurements that are high in both precision and accuracy. The conductivity measurement is performed in a cylindrical glass cell with a volume of 1.51 cm 3 containing three electrodes which ensures that the measurement is only affected by the volume within the cell (Gregg & Hess, 1985; Pederson, 1973; Pederson & Gregg, 1979). To be precise, the cell measures resistance, R cell , which is converted to the conductivity of the water, σ , by taking into account the cell geometry: $$${R}_{\mathit{cell}}=\frac{\rho l}{A}=\frac{l}{A\sigma }$$$ with $$\rho =\frac{1}{\sigma }$$ the resistivity of the water, l the effective length of the conductivity cell (which depends on cell length and water velocity though the cell), and A the cross‐sectional area of the sampled water.…”