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Page créée avec « == Introduction == An analog temperature sensor is pretty easy to explain, its a chip that tells you what the ambient temperature is! Fichier:TMP36-intro.jpg These sens... »
== Introduction ==
An analog temperature sensor is pretty easy to explain, its a chip that tells you what the ambient temperature is!
[[Fichier:TMP36-intro.jpg]]
These sensors use a solid-state technique to determine the temperature. That is to say, they don't use mercury (like old thermometers), [http://en.wikipedia.org/wiki/Bimetallic_strip bimetalic strips] (like in some home thermometers or stoves), nor do they use [http://en.wikipedia.org/wiki/Thermistor thermistors] (temperature sensitive resistors). Instead, they use the fact as temperature increases, the voltage across a diode increases at a known rate. (Technically, this is actually the voltage drop between the base and emitter - the Vbe - of a transistor.) By precisely amplifying the voltage change, it is easy to generate an analog signal that is directly proportional to temperature. There have been some improvements on the technique but, essentially that is how temperature is measured.
[[Fichier:TMP36-pinout.jpg]]
Because these sensors have no moving parts, they are precise, never wear out, don't need calibration, work under many environmental conditions, and are consistant between sensors and readings. Moreover they are very inexpensive and quite easy to use.
== Quelques informations ==
These stats are for the temperature sensor in the Adafruit shop, the [http://www.ladyada.net/media/sensors/TMP35_36_37.pdf Analog Devices TMP36] (-40 to 150C). Its very similar to the LM35/TMP35 (celsius output) and LM34/TMP34 (farenheit output). The reason we went with the '36 instead of the '35 or '34 is that this sensor has a very wide range and doensn't require a negative voltage to read sub-zero temperatures. Otherwise, the functionality is basically the same.
* Taille: boitier TO-92 à 3 broches (similaire à un transistor)
* Prix: ~2.50 eur disponible chez [http://mchobby.be/PrestaShop/product.php?id_product=59 MCHobby]
* Gamme de température: -40°C a 150°C / -40°F a 302°F
* Tension de sortie: 0.1V (-40°C) to 2.0V (150°C) mais la précision diminue après 125°C
* Tension d'alimentation: 2.7V a 5.5V
* Courant de charge: 0.05 mA
* [http://www.analog.com/en/mems-sensors/digital-temperature-sensors/tmp36/products/product.html Fiche technique]
== Comment mesurer la température ==
Comment calculer la température
Il faut donc convertir la tension analogique en degré.
Comme le TMP36 permet de mesurer des température négatives, le 0 degré Celsius est placé à une offset de 500 milliVolts.
Ainsi, toute mesure inférieur à 500 mv correspondra à une température négative.
[[Fichier:TMP36-Graph.png]]
La formule est la suivante pour le TMP36:
<nowiki>Temp en °C = ( Tension_de_sortie_en_milliVolts - 500) / 10</nowiki>
Donc, si la tension de sortie est de 1 Volts, la température correspondante est de<br /> (1000 - 500)/10
Soit 50 degrés Celcius.
<small>Source: [http://learn.adafruit.com/tmp36-temperature-sensor AdaFruit]</small>
{{ADF-Accord}}
{{MCH-Accord}}
An analog temperature sensor is pretty easy to explain, its a chip that tells you what the ambient temperature is!
[[Fichier:TMP36-intro.jpg]]
These sensors use a solid-state technique to determine the temperature. That is to say, they don't use mercury (like old thermometers), [http://en.wikipedia.org/wiki/Bimetallic_strip bimetalic strips] (like in some home thermometers or stoves), nor do they use [http://en.wikipedia.org/wiki/Thermistor thermistors] (temperature sensitive resistors). Instead, they use the fact as temperature increases, the voltage across a diode increases at a known rate. (Technically, this is actually the voltage drop between the base and emitter - the Vbe - of a transistor.) By precisely amplifying the voltage change, it is easy to generate an analog signal that is directly proportional to temperature. There have been some improvements on the technique but, essentially that is how temperature is measured.
[[Fichier:TMP36-pinout.jpg]]
Because these sensors have no moving parts, they are precise, never wear out, don't need calibration, work under many environmental conditions, and are consistant between sensors and readings. Moreover they are very inexpensive and quite easy to use.
== Quelques informations ==
These stats are for the temperature sensor in the Adafruit shop, the [http://www.ladyada.net/media/sensors/TMP35_36_37.pdf Analog Devices TMP36] (-40 to 150C). Its very similar to the LM35/TMP35 (celsius output) and LM34/TMP34 (farenheit output). The reason we went with the '36 instead of the '35 or '34 is that this sensor has a very wide range and doensn't require a negative voltage to read sub-zero temperatures. Otherwise, the functionality is basically the same.
* Taille: boitier TO-92 à 3 broches (similaire à un transistor)
* Prix: ~2.50 eur disponible chez [http://mchobby.be/PrestaShop/product.php?id_product=59 MCHobby]
* Gamme de température: -40°C a 150°C / -40°F a 302°F
* Tension de sortie: 0.1V (-40°C) to 2.0V (150°C) mais la précision diminue après 125°C
* Tension d'alimentation: 2.7V a 5.5V
* Courant de charge: 0.05 mA
* [http://www.analog.com/en/mems-sensors/digital-temperature-sensors/tmp36/products/product.html Fiche technique]
== Comment mesurer la température ==
Comment calculer la température
Il faut donc convertir la tension analogique en degré.
Comme le TMP36 permet de mesurer des température négatives, le 0 degré Celsius est placé à une offset de 500 milliVolts.
Ainsi, toute mesure inférieur à 500 mv correspondra à une température négative.
[[Fichier:TMP36-Graph.png]]
La formule est la suivante pour le TMP36:
<nowiki>Temp en °C = ( Tension_de_sortie_en_milliVolts - 500) / 10</nowiki>
Donc, si la tension de sortie est de 1 Volts, la température correspondante est de<br /> (1000 - 500)/10
Soit 50 degrés Celcius.
<small>Source: [http://learn.adafruit.com/tmp36-temperature-sensor AdaFruit]</small>
{{ADF-Accord}}
{{MCH-Accord}}