Measuring Internal Waves with Thermistor Chains & Fast-Sampling Current Meters

Internal waves can be effectively measured by profiling the water-column temperature every 30 seconds or so. A new 14-sensor thermistor-chain manufacturing technology has been developed that features an integral Kevlar mooring tension line; the thermistor chain and mooring line are one piece! Special termination methods are described that allow twist-free conenction to the data recorder, also mounted on the mooring line. To measure internal waves, fast-response thermistor breakouts have been developed. The method has been proven in field use at sites where thermistor chains have always failed in the past. Chains of up to 2,000 meters in length may be made. Low-cost circuits that allow temperature measurement to 5m degrees C are described. A companion burst-recording current meter has been made to measure the internal-wave currents at one spot. The current meter has been made to measure the internal-wave currents at one spot. The current meter and temperature-chain may be combined in one instrument. Low-power circuits, data compaction techniques and a high-capacity tape recorder are utilized in both instruments to allow 6 to 12 month deployments. Both instruments use 6-inch housings and standardized system design methodologies to allow easy further expansion.