A Fast and Accurate Thermistor String¹

Abstract

A ''fast thermistor string'' has been built to accommodate the scientific need to accurately monitor internal wave activity in shelf seas and above sloping bottoms in the ocean. The performance of the thermistors and their custom-designed electronics allow temperature variations to be registered at an estimated relative accuracy better than 0.5 mK with a response time faster than 0.25 s. Quantization noise is less than about 40 K and dominates instrumental noise. Currently, the string holds 32 sensors, which are sampled within 4 s. When sampling every 30 s, the batteries and the memory capacity of the recorder allow deployments up to 3 months. In all respects, this performance is about an order of magnitude superior to thermistor strings currently available commercially. Moored in combination with an acoustic Doppler current profiler the thermistor string provides data to estimate directly quasi-turbulent (high-frequency internal wave band) vertical temperature fluxes and flux gradients. Examples of field observations are given, which show enhanced levels of temperature variance extending above the canonical internal wave spectral levels near the buoyancy frequency, and detailed variations of high-frequency internal wave variability.

Philosophy and Application of High-Resolution Temperature Sensors for Stratified Waters

“…Initially, in version NIOZ1: 32, later in version NIOZ2: 128, T-sensors were connected via cables to a central data logger and power supply unit [ 14 , 15 ], respectively. After considerable connection and leakage problems, it was decided to construct stand-alone self-contained sensors: Version NIOZ3 [ 16 ].…”

Solibore‐induced sediment resuspension in the Faeroe‐Shetland Channel

“…High resolution measurements over the bottom 30 m of the water column at A2 were enabled by the use of a fast sampling, accurate thermistor string [ van Haren et al , 2001] and a 600 kHz ADCP, each sampling once per minute and with a vertical resolution of 1 m and 0.5 m respectively. The resemblance of the intrusion to a solibore is clear as a bore‐like face is followed by a wave train consisting of approximately 5 asymmetric waves extending into the thicker overlying layer (Figure 4a).…”

Internal wave band eddy fluxes above a continental slope

“…The thermistor string, built specifically for internal wave band flux measurements (van Haren et al, 2001), extended over the range 2.9 -33.9 m at 1-m resolution. It was located within the beam spread of the upward-looking ADCP.…”