• 센서학회지
• /
• 제25권1호
• /
• pp.65-70
• /
• 2016

We devised a method to control the temperature of a liquid bath as low as $-100^{\circ}C$ using the duty cycle control of a solenoid valve. The solenoid valve controls the flow of liquid nitrogen that we used as a cryogen in this system. By controlling the duty cycle of a solenoid valve using feedback from the measured temperature of the liquid bath, we were able to achieve temperature stability within ${\pm}19mK$ around $-100^{\circ}C$. We also demonstrated that by taking average values of the temperature readings for sequence of measurements from more than one thermometer, it is possible to use this system for the calibration of thermometers within 3 mK. This system and the control method can be used for the precise temperature control in the range between $0^{\circ}C$ and $-100^{\circ}C$, where commercially available precision baths are much expensive and hard to be built in customized configurations.

• Ocean and Polar Research
• /
• 제31권1호
• /
• pp.1-9
• /
• 2009

When evaluating acoustic methods for measuring physical parameters in the ocean, economical and technical considerations are paramount. As an indirect method of estimating ocean dynamics, acoustic tomography has advantages over more conventional approaches. It allows the reconstruction of temperature and flow fields from the acoustic impulse time-of-flight measured along the rays propagating from the source to the receiver. However, many problems require complicated and expensive systems. To use the acoustic tomography method to best effect, developing hardware systems with sources and receivers mounted permanently on the sea bottom is crucial. Akulichev et al. presented some experimental results from shallow zones of the World Ocean that served as a motive for developing a multifunction system with acoustic hardware and software. Here we present technical features and the sea test results of the system.

• 센서학회지
• /
• 제18권2호
• /
• pp.116-121
• /
• 2009

Pressure-controlled sodium heat pipe furnace was designed and fabricated, and its characteristics was investigated. Pressure control system was controlled within ${\pm}0.5\;Pa$ at 150 kPa and the stability of pressure was decreased to ${\pm}2.5\;Pa$, when the pressure-controlled system connected with the heat pipe. The melting curve of Ag fixed-point realized well by the adiabatic method using the pressure-controlled sodium heat pipe furnace and its accuracy showed ${\pm}2.27\;mK$ from the calculation of 20% to 80% at the plateau. The freezing curve of Ag fixed-point also realized and its plateau value was 2.23 mK lower than that of the melting curve.