Chen [6] measured the junction temperature using this approach, and obtained the results that were consistent selleck inhibitor with those obtained using the emission peak energy shift approach. The infrared ray scheme is an effective means of measuring the temperature of an LED, but it measures only the temperature on the top of the chip, which is not the junction temperature. Senawiratne [7] estimated used thermal resistance measurement to determine the measurement junction temperature of a light emitting diode, increasing the driving currents in increments at increments of 10 mA to 250 mA. Xi [8] examined a theoretical model of the dependence of the forward voltage of a diode on junction temperature. Chen [9] applied micro-electro-mechanical Inhibitors,Modulators,Libraries systems (MEMS) techniques to develop a resistance temperature detector (RTD).
Chen [10] also adopted Y-doped BaZrO3 thin films to make an RTD high-temperature sensor, and the resistance temperature detector is also applied in numerous domains [11,12]; this method is quite effective. Although a thermal resistance measurement is frequently employed, it is inaccurate because a change in the current Inhibitors,Modulators,Libraries produces a pulse, but the current can only be measured when it is stable.This work presents a novel approach based on micro-electro-mechanical-systems (MEMS) technology to fabricate a flexible micro temperature sensor on a stainless steel foil substrate (SS-304 with a thickness of 30 ��m) in order to monitor in-situ the junction temperature of a light emitting diode. This fabrication technique has the advantages of: (1) small size, (2) high sensitivity, (3) flexible but precise measurement positions, Inhibitors,Modulators,Libraries and (4) mass production.
2.?Methodology2.1. Thermal Resistance MeasurementPreviously, the Inhibitors,Modulators,Libraries junction temperature of LEDs has been determined from changes in the forward voltage [13]. Thermal resistance was measured by exploiting the fact that resistance increases with temperature, and the voltage thus declines. Figure 1 presents the circuit diagram. Thermal resistance is measured as follows: (1) Input an initial measured current (IM) and measure the initial voltage (VF0); (2) Input a higher heating current (IH) until the temperature is stable; (3) Change the measured current (IM) rapidly, and measure the voltage (VFSS) after heating; (4) Compare VF0 and VFSS following calibration to yield the temperature of the LED chip, as shown in Figure 2.
Figure 1.Circuit illustration of thermal resistance Entinostat measurement technology.Figure 2.Measuring procedure of thermal resistance measurement technology.Although measurements of thermal resistance are useful, this approach cannot always be applied to measure temperature, and a pulse is produced when the current is changed. The pulse affects the voltage, destabilizing the measured temperature.2.2. Resistance Temperature DetectorIn this work, the temperature sensor was selleck chemicals Ruxolitinib a resistance temperature detector (RTD).