Posts Tagged ‘Measurements temperature’

Electronic Thermometer by LM35 and LM3914

As shown in the schematic, temperature sensor of our electronic thermometer is LM35DZ. There are some kinds of LM35 IC, since it is cheap and easy to find we used LM35DZ in our project. It measures from 0°C to 100°C with a very linear output graph.For one degree change, it increases its output 10mV.On theElectronic Thermometer Schematic other hand, this circuit measures temperature values only between +10°C and +39°C.

2 numbered (middle) pin of the sensor is connected to the 5 numbered pins of LM3914 ICs. So every IC determines how many leds of bargraph will bright due to the analog signal received from the sensor. 2.2 microfarad tantal capacitors are connected between the 2 and 3 numbered pins of LM3914. Resistors in the circuit have %1 tolerance values.

Source:http://www.circuit-projects.com/electronic-thermometer-project-by-lm35-and-lm3914.html
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PIC Dual Temperature Meter by PIC16F628

This is extremely simple to build PIC Temperature meter that allows to measure temperature in two different locations at the same time. Never before such a useful and powerful circuit could be built with so little components and yet provide endless possibilities. This is all possible thanks to the use of PIC16F628 microcontroller and 2×16 character LCD display that act like a small computer which can be customizable thanks to upgradeable hex firmware.

Presented PIC temperature meter uses two very exciting DS18S20 digital temperature sensors that come in convenient TO92 package. Unlike regular sensors where temperature readings are passed as varying voltage, DS18S20 passes temperature information in a digital format as data. This brings many new possibilities and enables to pass temperature information over much longer distances just over a two wire cable. With this temperature can be measured in different locations at the same time and away from the main circuit board. With regular sensors which rely on the varying voltage cables must be as short as possible because longer wires introduce stray resistance that bring unreliable readings.

Read More Source:http://electronics-diy.com/pic_temperature_meter.php
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Measurement Of Temperature

When power transistors are used, they may tend to over heat. Likewise resistors may also overheat in the event of faults or short-circuits. The knowledge of their temperatures may be advantageous. In addition, measurement of temperature constitutes a basic necessity in day-to-day life.

Measuring the temperature of a body, depends upon the establishment of thermo-dynamic equilibrium between the body and the device used to sense the temperature. In practice, this condition is rarely attained since it is difficult to establish complete instantaneous equilibrium. Hence great care must be exercised in choosing a method suited to the problem so that satisfactory conditions for temperature measurements are obtained. Temperature sensors possess thermal characteristics dependent largely on their size and shape and the materials from which they are made. These characteristics affect precise measurements. The introduction of a temperature sensor into a body tends to modify the temperature conditions at that point. In most cases the sensor is connected to a recording instrument by means of an intermediate system, along which the signal is carried. The intermediate system and the recorder may be subject to temperature and other changes. Hence compensating devices become a necessity to reduce or eliminate errors.

The measurement of temperature in our instrument depends on the fact that the forward voltage drop of a silicon diode changes by about – 2 millivolts per degree centigrade. Thus, by measuring the change in forward voltage of silicon diode kept in a temperature probe, the voltage drop can be converted into temperature.

Read more source:

http://schematics.blogspot.com/2006/10/diode-thermometer.html

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