Development and Testing of a Multiplexed Temperature Sensor

Abstract

Researchers studying phenomena associated with steep surface temperature gradients, such as boiling, need to be able to obtain a detailed surface temperature distribution. Such a distribution can be obtained by taking measurements at a number of discrete locations on the surface using multiple individual temperature sensors. Because each sensor requires at least two electrical connections, this approach has historically been limited to relatively few temperature measurements; the most extensive measurements made this way are still limited to a 10 × 10 array. A new temperature sensor has been developed to address this measurement problem. The new sensor consists of a 32 × 32 array of diode temperature sensors in a 10.24 mm2 area, with each component diode measuring 100 × 100 micron^2. Unlike previous array-type sensors, the new sensor uses a multiplexing scheme to reduce the number of external leads required; only 64 leads are required to obtain measurements from over 1000 individual temperature sensors. The new sensor also incorporates eight resistive heater elements to provide the heat flux to initiate and sustain boiling. The heaters are capable of delivering up to 100 W/cm^2. This dissertation describes the design and testing of the new temperature sensor and the supporting hardware and software. The system is demonstrated by determining the local heat transfer coefficients for a jet of FC-72 from a 0.241 mm diameter nozzle. The surface temperature distribution is measured for various combinations of applied heat flux, jet velocity, and nozzle standoff distance; these measurements are then used to determine the local heat transfer coefficient distribution. These measured values compare favorably to those predicted using several correlations available in the literature.