In this post we are going to make you familiar with some of the concepts related to bimetallic strip thermometer such as what are bimetallic thermometers and where these are used .We will also discuss the working principle , construction and various features of these type of thermometers . Let us know what basically bimetallic thermometers are and how these are different from other type of thermometers .
Definition & construction of Bimetallic thermometer
Bimetallic strip is a mechanical element that senses temperature and convert it into mechanical displacement. This mechanical action can be used to activate a switching mechanism in order to get electronic output. So bimetallic strip is a device that measure temperature and give output in for of mechanical displacement of electrical output .
Bimetallic thermometers are the thermometers made of bimetallic strips which is formed by joining two different metals that have different thermal expansion coefficients. There are number of techniques that can be used to bind 2 layers of different metals .These techniques include riveting, bolting and fastening .Other most commonly used method is welding.
Bimetallic strip Images
Working Principle of bimetallic strip
Bimetallic strip work on 2 principles
- When change in temperature takes place , either expansion or contraction occurs in metals .
- The rate of expansion or contraction depends on the temperature co-efficient of expansion of the metal. This temperature coefficient is different for different metals. Therefore difference in thermal expansion rates is used to produce deflections and these deflections are proportional to temperature changes.
It means that two dissimilar metals behave in a different manner when exposed to temperature variations due to owing to different thermal expansion rates. One layer of metal expands / contracts more than other metal layer of metal due to which there occurs bending or curvature change of strip.
Simple explanation of Bimetallic strip thermometer
Fix one end of a straight bimetallic strip and then start heating the strip . As the strip is heated, other end( end of the strip that is not fixed ) tends to curve away from the side that has the greater coefficient of linear expansion.
Brass and steel are common metals that are bonded together in a bimetallic strip.
Explanation of this temperature measuring device
Bimetallic thermometer features
- These thermometers work best at higher temperatures. This is due to the fact that their sensitivity and accuracy is less at low temperatures.
- There are various designs of Bimetallic strip thermometers available .Most common and popular design flat spiral .Other designs are single helix or multiple helix form.
- Certain customization can be done in Bimetallic thermometers such as fixing a pen to the pointer. With this pen one can make recordings on a circling chart.
- Bimetallic strips are usually coiled into spirals in order to make them compact (Coiled spirals improves the sensitivity)
- The bimetallic strip can be scaled up or down.