Investigation of the Temperature Characteristics of the IN4148 Signal Diode and Its Suitability for use as a PTC Temperature Sensor.
This paper presents an investigation of the temperature characteristics of the IN4148 signal diode and its suitability for use as a PTC temperature sensor. The IN4148 signal diode with a Negative Temperature Coefficient of -2mV/OC was used in the implementation of the sensor for a temperature range of 27OC to 100OC.A 5V6 Zener diode was used to maintain a constant voltage across the sensor placed in a ¼ bridge network. The output of the sensor was amplified by a differential amplifier and the negative temperature coefficient was converted to a positive coefficient by the use of an inverter circuit. The results obtained show an increase in the temperature coefficient from-2mV/OC of the diode to -40mV/OC at the output of the differential amplifier. The temperature coefficient is converted to positive with a value of 10mV/OC at the inverter output. This sensor circuit finds application with easy calibration due to the positive temperature coefficient in control of heating systems with a temperature range of 27OC to 100OC.