Temperature Sensor ICs Simplif

文章摘要：Figure 7. A temperature sensor that transmits a square wave whose frequency is proportional to the measured temperature in Kelvin forms part of a heater controller circuit.Figure 8. This temperature sensor transmits a square wave whose period is proportional to the measured temperature in Kelvin. Be

Temperature Sensor ICs Simplif,标签：计算机控制技术,工厂电气控制技术,http://www.88dzw.com

Figure 7. A temperature sensor that transmits a square wave whose frequency is proportional to the measured temperature in Kelvin forms part of a heater controller circuit.


Figure 8. This temperature sensor transmits a square wave whose period is proportional to the measured temperature in Kelvin. Because only a single line is needed to send temperature information, just a single optoisolator is required to isolate the signal path.

Figure 9, a truly novel approach, allows up to eight temperature sensors to be connected on this common line. The process of extracting temperature data from these sensors begins when the microcontroller's I/O port strobes all the sensors on the line simultaneously. The microcontroller is then quickly reconfigured as an input in order to receive data from each of the sensors. The data are encoded as the amount of time that transpires after the sensors are strobed. Each of the sensors encodes this time after the strobe pulse within a specific range of time. Collisions are avoided by assigning each sensor its own permissible time range.


Figure 9. A microcontroller strobes up to eight temperature sensors connected on a common line and receives the temperature data transmitted from each sensor on the same line.

The accuracy achieved by this method is surprisingly high: 0.8°C is typical at room temperature, precisely matching that of the IC that encodes temperature data in the form of the frequency of the transmitted square wave. The same is true of the device that uses the period of the square wave.

These devices are outstanding in wire-limited applications. For example, when a temperature sensor must be isolated from the microcontroller, costs are kept to a minimum because only one optoisolator is needed. These sensors are also of great utility in automotive and HVAC applications, because they reduce the amount of copper running over distances.

Anticipated Temperature Sensor Developments

IC temperature sensors provide a varied array of functions and interfaces. As these devices continue to evolve, system designers will see more application-specific features as well as new ways of interfacing the sensors to the system. Finally, the ability of chip designers to integrate more electronics in the same die area ensures that temperature sensors will soon include new functions and special interfaces.

A similar version of this article appeared in the January 2000 issue of Sensors.

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