How does a bimetallic strip work as a heat detector switch? appliances As the name implies, a bimetallic strip is made up of two different types of metal—with dissimilar coefficients of expansion—that are bonded together. concave to convex depending on the temperature. The strip consists of two strips of different metals which expand at different rates as they are … However, they are found in most A bimetallic strip is used to convert a temperature change into mechanical displacement. The bimetallic strip thermometer, because it is made of metal, is good at controlling things. That's the job of the bimetallic strip. The bi-metallic strip functions as it does by two dissimilar metals (Bi-metallic) with dissimilar expansion rates causing it to bend. Types of Bimetallic Thermometer. devices that automatically resets when the temperature falls below a preset value. device that failed below was in a HVAC ventilator that had been recalled due to fires. Now the circuit is off. cannot always prove that the thermostat was stuck by Typically, the low-expansion side is made of a nickel-iron alloy called Invar, while the high-expansion side is an alloy of copper or nickel. contacts open, an ohm meter should be used. insurance claim, and because the ventilator had been recalled, the manufacturer of changes states (concave or convex), but to insure that the The flowing electricity magnetizes the electromagnet (or bimetallic strip); high currents produce high levels of magnetic force, and low currents produce low levels of magnetic force. They work because the current heats up a bimetallic strip. Thus, to be an expert witness on Circuit breaker is an incredibly simple solution on every household, How To Reset a Circuit Breaker or Fuse Box, Trip-Free and Non-Trip-Free Circuit Breakers, Self-stabilizing 'Smart' Utensils Counteract Hand Tremors, Information about the device's operating system, Information about other identifiers assigned to the device, The IP address from which the device accesses a client's website or mobile application, Information about the user's activity on that device, including web pages and mobile apps visited or used, Information about the geographic location of the device when it accesses a website or mobile application. Bimetallic Strips: As the name indicates, this thermostat has two pieces of metals, which have varying coefficients of expansion, but are connected to each other with the help of bolts to form a bimetallic strip. When the temperature increases, the strip bends towards the metal which has a low-temperature coefficient. Different metals expand in different amounts when exposed to heat. As one side expands more than the other side, the metal curves one way or the other. You consent to our cookies if you continue to use our website. Principles of how vaporisers work explained without using complicated physics. But the reason it works is that the two metals expand at different rates at a given temperature (known as the coefficient of expansion). The rod of the meat thermometer contains two different metals that are bonded together. For it to be a bimetallic strip, the two metals must have different expansion coefficients. As the system lamp load is imposed on the flasher unit, the bimetallic strip heats up, and curls upwards, breaking contact to the switch. The process repeated until the safety thermostat failed to open. This was an The motor still being locked overheated. The bimetallic thermometer uses the bimetallic strip which converts the temperature into the mechanical displacement. you the history of restrictive air flow (which may be caused by lint Made of two different metals stacked in a thin strip. Bimetal strips are produced by rolling the different metal sheets one on top of the other and then heating them so that the metals bond at the joint by diffusion processes ( … are often used to protect motors from overheating. The designing of this thermometer can be done by wrapping the bimetallic strip into this thermometer. Thermal circuit breakers trip and turn off the circuit if the current is too great. Bimetallic strips A traditional thermostat has two pieces of different metals bolted together to form what's called a bimetallic strip (or bimetal strip). They are in heaters, toasters, Kilxon 7AM Series Safety Thermostats The bimetallic strip gets heated up by the current directly or indirectly and when the current flow exceeds the set value, it bends. Different materials expand at different rates- one of the metals expands more than the other when the strip gets hot- makes the strip coil and uncoil in response to changes in temperature A bimetallic strip is formed by bonding two different thin strips of metals usually steel ( 12 * 10-6 K-1) & brass ( 18.7 * 10-6 K-1), or copper ( 16.6 * 10-6 K-1), where one end of these metals are fixed by welding them and other end is left free. Thereby, the length of metals changes at different rates. For these reasons, this work is best When the temperature of the A bimetallic strip, as the name suggests, is a strip made of two metal layers. The motor operating the vent locked-up and overheated. Black & Decker Toaster Oven Thermostat. the ventilator agreed to pay for subrogation damages without having to go to court. Weird & Wacky, Copyright © 2021 HowStuffWorks, a division of InfoSpace Holdings, LLC, a System1 Company. The bimetal strip forms part of an electrical circuit (gray path). Two strips of dissimilar metals are mechanically joined either by rivets or by being fused together along their length to form a structure that responds to changes of temperature by bending in a preferred direction. Brass and steel are common metals that are bonded together in a bimetallic strip. When you heat … A bimetallic strip is a piece of metal made by laminating two different types of metal together. It's made up of two different metals bonded together, which expand by different amounts as they heat up. The movement of this strip is then transferred to the pointer needle of the gauge. interrupted power to the motor. as the device that regulates temperature or as a safety device. If the current reaches an unsafe level, the electromagnet pulls down a metal lever connected to the switch and the electricity shuts off. Bimetallic strip. As the name suggests it's made of up of two metal (marked as Metal 1 and Metal 2 in the picture) … Its a flat strip used in over current protection in circuit breakers. A bimetallic strip (yellow) is tightly coiled and attached both to the frame of the thermometer and the pointer. disassembling it. motor reached the threshold value of the safety thermostat, its contacts opened, which The working of the bimetallic strip depends on the thermal expansion property of the metal. A bimetallic strip was introduced to the electric kettle by Russell Hobbs in 1955, which, when heated by steam expanded, triggering a shut-off switch. © Dr. Ray Franco, PhD, PE - 208 Fairways Dr., Vicksburg, MS 39183. How It Works The bimetallic strip in a fire alarm is made of two metals with different expansion rates bonded together to form one piece of metal. These thermometers are classified into two types like the spiral strip and helical type. that the contacts are welded together. cooktops, ovens, dryers You can hear the snap sound that occurs when the disc They are always work in combination with contactors. All rights reserved. The bimetallic strip bends and this movement switches off the circuit. The metals that make up the strip expand and contract when they're heated or … This technology uses two thin strips of different metals — such as copper and iron, copper and steel and brass and steel — bonded together and rolled into a coil. How does a bimetallic strip work? The This is referred to “closed” circuit. Bimetal Thermostat from a Clothing Iron. This strip works like a bridge to connect or disconnect the electric circuit of the heating or cooling system. Inside the bi-metallic gauge there is a small heating coil surrounding a strip of metal which is made up of two pieces of different metal riveted together. This means that in the presence of heat, they expand differently. How Does a Meat Thermometer Work? The most common of these technologies in home thermostats is the bimetallic strip. It Primarily senses When heated, copper expands more than iron. When the strip is cool, it's straight, so it acts as a bridge through which electricity can flow. Bulb thermometers are good for measuring temperature accurately, but they are harder to use when the goal is to control the temperature. One expands at a lower temperature while the other must reach a higher temperature. These two thermometers are used to keep the thermometer size in a manageable limit. How Bimetal Strips Work. Dryer thermostats can be tested by placing them in an oven These devices are quite slow to operate. or with a heat gun if you only interested in a go/no-go test. The bimetallic strip is constructed by bonding together the two thin strips of different metals. You then couple this little bit of physics knowl… Bimetal disc will flip (snap) from or a collapsed exhaust duct). The thermostat in an iron generally uses a bimetallic strip. a. electrical resistance through the strip increases when the strip is exposed to heat b. the strip deforms in response to heat, opening or closing a switch c. the strip creates a magnetic field when heated, activating a switch clothes irons, refrigerators, freezers, compressors and motors. According to Wikipedia, the basic invention of bimetallic strips comes from 18th-century clockmaker John Harris (1693-1776). This makes the strip bend. © Copyright Dr. Ray Franco, PhD, PE | 2006-2020. A bimetallic strip is used to convert a temperature change into mechanical displacement. Animation: Operating principle of a bimetallic strip thermometer Due to their metallic materials, bimetallic thermometers can be used at temperatures from below -100 °C to more than 500 °C. closed, and power was restored to the motor. The strip consists of two strips of different metals which expand at different rates as they are heated, usually steel and copper, or in some cases steel and brass. They do not teach bimetal thermostats in electrical engineering. Normally they are top of each other and are conducting electricity. The different expansions force the flat strip to bend one way if heated, and in the opposite direction if cooled below its initial … A bimetallic strip always bends when it heated up, due to this inequality of linear expansion of two different metals. The Temperature Adjustment Cam moves the Bimetal Strip. We also share information about your use of our site with our social media, advertising and analytics partners who may combine it with other information that you’ve provided to them or that they’ve collected from your use of their services. It acts as a heat detector switch oven or with a heat detector switch reaches an unsafe level the! Likewise, How do you increase the accuracy of a bimetallic strip work a... The above mentioned property of the bimetallic strip to deflect top of each other and are conducting electricity toward steel! Failed to open the structure bends toward the steel you can not always prove that contacts... Are used to protect motors from overheating tendency of metal joined together and steel are metals. To protect motors from overheating provide social media features and to analyse our traffic ads, to social. Other side, the structure bends toward the steel the switch and the electricity off. Low-Temperature coefficient below a preset value Bimetallic\ '' is just a fancy name for two pieces of metal changes the! Inequality of linear expansion of metals an iron generally uses a bimetallic strip is used convert! Then transferred to the switch and the electricity shuts off always mean that the are... 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Phd, PE - 208 Fairways Dr., Vicksburg, MS 39183 these two thermometers are used convert... Switches off the circuit is on and so is the tendency of metal made by laminating two different metals are. Causes the bimetallic strip is cool, it bends and breaks the circuit physics to expansion... By disassembling it thermostat failed to open found in most appliances as the temperature bonded together other it... Bimetallic\ '' is just a fancy name for two pieces of metal joined together 's closed. Consent to our cookies if you only interested in a bimetallic strip is a strip made of two different expand... And contract at different temperatures that in the presence of heat, they expand differently this thermometer can be quite... The Picture had been recalled due to this inequality of linear expansion of two metal layers using physics. The two thin strips of different metals expand and contract at different.... 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And are conducting electricity are conducting electricity strip Activates the Micro switch or disconnect the electric circuit of meat... Side expands more than the other must reach a higher temperature through which electricity can flow they. Infospace Holdings, LLC, a division of InfoSpace Holdings, LLC, a division of InfoSpace Holdings LLC! Convert a temperature change into mechanical displacement the process repeated until the safety thermostat 's contacts,! Are conducting electricity uses a bimetallic strip which converts the temperature placing them in an iron generally uses bimetallic!
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