If you consider that a temperature sensor-project based on the easiest way to do this, a sensor for the temperature coefficient of the diode. This coefficient is a measure of how a junction diode responds to temperature and knows all the electronics that is-2.1mV per degree centigrade.
There are two problems with the use directly:
1. It's Going Down.
2. It is very small and uncomfortable to read.
3. Notcalibrated.
Direction
Of course, with operational amplifiers, you can solve these problems and the first for the problem, you can create a REG, in its reverse mode, so now you have an output ranging from 2.1mV per degree Celsius to be used .
Output Size
For the second problem would be much easier to use if the actual return could be read directly with a voltmeter for example 25 degrees Celsius of 250mV is much easier to read than 52.5mV.(52.5/2.1 = 25).
What we really want is one output, the increase in linear 10mV increments for each grade by grade is a good value for comfortable reading on a voltmeter.
You can do it with an ADC with a gain of 4.76191.
If you're an engineer who immediately see the problem - is lagging far behind the 4 decimal places, which means that you will need super precision resistors to get the job done. Of course, you can use a standard 4.7k resistance to about oneapproximate result, but for measurements of temperature, you really want an accurate production.
For example, with a gain of 4.7 to 25 degrees results in a Celsuis performance 246.75mV say that it is already in error by half a degree.
Calibration
As with all circuits discrete diodes have the device at a temperature of note, for example, by subtracting the diode in very cold water or calibrate the diode voltage corresponding with a different startREG.
Comfortable CI: LM35
While you can do all these different actions and to make a discrete version of a project, a very comfortable temperature measurement IC is not all for you.
This is the LM35 temperature IC to solve all these problems:
1. Produces an output that increases with temperature.
2. Increase generate output 10mV per degree centigrade.
3. It is fully calibrated.
Which methodUse either project specific or a simple way to measure IC, the output is used to feed them the ADC input of a microcontroller.
You can then use the microcontroller, a series of temperature readings over a period that you want at any time interval you need to do so it is easy to make a temperature of draft registration.
