Glass And Infrared Thermometer

Glass thermometer:

In an indoor thermometer and outdoor thermometer, these two are based on a conventional liquid in glass thermometer. The stem present in the outdoor thermometer is connected to the bulb by a long semi rigid capillary or flexible capillary. On the stem the temperature scale is marked. At the bulb the temperature is actually measured.

Ambient modifications are hard to attain with this system and are not frequently done. Compared with the conventional precision thermometer does not give an accurate result. For low cost application this is hard to use. The main problem occurs at accuracy , when the bulb and the stem are at different levels. There is a change in pressure head due to the change in the readings. We can notice the problems when there is a change in the ambient temperature of the indoor part; it can change the readings and temperature if the device is kept out.


By making the small diameter of capillary and bulb larger the effects are minimized. So there is change in the temperature and it produces the large changes in the liquid column in the stem. It will tend to marsh the lesser change affected by the variations in the indoor temperature.

Commonly used liquids are alcohol and toluene. They have higher temperature coefficient of expansion. They do not boil or freeze in the temperature range of notice.

Infrared thermometer

Infrared thermometer is a thermometer which infers temperature from a portion of the thermal radiation. It is also known as black body radiation. The infrared thermometer is also called as a laser thermometer. By using this thermometer we can measure the temperature from a distance.


The temperature is determined by using the infrared energy emitted by the object and its emissivity. Infrared thermometers are a subdivision of devices known as “thermal radiation thermometers“.

In some cases we can see that the false reading is near the ambient temperatures. The lens present in the infrared thermometer are used to convert the radiant power to an electrical signal so it can display the range of the temperature after presence is compensated for ambient temperature. The infrared thermometer is useful for calculating temperature under conditions where thermocouples or other probe type sensors cannot be recycled or do not create correct data for a change of reasons.

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