Posted on May 12, 2012 11437
The temperature sensor provides an input to pin 3 of the NE5037 of 32 mV/Â°C. This 32 mV is the value of one LSB for the NE5037. The LM334 is a three-terminal temperature sensor and provides a current of 1 p.A for each degree Kelvin. The 32-KO resistor provides the 32 mV for each microamp through it, while the transistor bleeds off 273 p.A of the temperature sensor (LM334) current. This bleeding lowers the reading by 273 K, thus converting from Kelvin to Celsius. To read temperature, conversion is started by sending a momentary low signal to pin 7 of the NE5037.
When pin 10 of the NE5037 becomes low, conversion is complete and a low is applied to pin 9 of the NE5037 to read data on pins 11 and through 16. Note that this temperature data is in straight binary format. The controller can be a microprocessor in a temperature controLapplication, or discrete circuitry in a simple temperature reporting application.