Flexible metallic film temperature sensors play an important role in some modern engineering applications such as temperature measurements of curved surfaces or interlayer structures with narrow gaps of industrial equipment (e.g. iron cores of generators, motors and transformers).
Platinum is generally used for metallic film temperature sensors thanks to its high accuracy and stability, but it is expensive. Recently, copper film temperature sensors are widely utilized for temperature measurement instead of platinum sensors as the design based on PCB technology allows cost-efficient fabrication, easy handling, and simple retrofitting and replacement. However, defects existing on the PCB leads result in the decline of the performance and stability of the sensor.
A research team led by Pak Yong Thaek, head of Semiconductor Institute, has developed a temperature measurement system for generator protection in consideration of the operation characteristics of generators. For this, they designed a new structure of temperature sensors and proposed a method to design the most suitable thermometer and communication hub for the conditions of power plants.
The system consists of sensors, one-channel and multi-channel thermometers and communication hubs.
The one-channel and multi-channel thermometers measure in real-time the temperature of local points, display the temperature values and output alarm sounds and protection relay signals. The thermometers also transmit measured data to the communication hub.
In order to avoid the lethal defects of PCB leads like disconnection and fall, detour leads are added to the new design. Thus, the copper film resistive lead of the sensor consists of four parts: main resistive lead, detour lead, correction lead and pads. In addition, 3-line mode is used to prevent low accuracy due to the connection wire from the sensor to the amplifing circuit.
The measurement range is -50~170℃ and the error is 0.5℃.
Tested for a long time of over 3 000 hours at 150℃, the sensor proved its reliability. The deviation rate of resistance of the sensor is less than 0.1%. TCR is 4.1×10-3℃-1 and the maximum current is 10mA.
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