One of the two cycling contacts energizes the controlled heating element and the other energizes a very small electric heating element attached to a bimetallic strip. The force from the heated bimetallic strip increases as its temperature rises until it overcomes the combined force from the cam follower, an unheated bimetallic strip that compensates for ambient temperature, and the permanent magnet allowing the cycling contacts open which interrupts the electric current to both heating elements. Both the bimetallic strip and the "burner" begin to cool. Eventually the heated bimetallic strip will no longer have enough force to overcome the force from the cam follower and the unheated bimetallic strip.
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The surface quality can be affected by factors such as temperature changes, internal stress in the substrate, or even bending effects that occur when combining materials with different coefficients of thermal expansion, similar to a bimetallic strip.
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A direct indicating dial thermometer really common in daily use devices (such as a patio thermometer or a meat thermometer) uses a bimetallic strip wrapped into a coil in its most used design. The coil changes the linear movement of the metal expansion into a circular movement thanks to the helicoidal shape it draws. One end of the coil is fixed to the housing of the device as a fix point and the other drives an indicating needle inside a circular indicator. A bimetallic strip is also used in a recording thermometer.
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Various types of glow starter A glow switch starter or glowbottle starter is a type of preheat starter used with a fluorescent lamp. It is commonly filled with neon gas or argon gas and contains a bimetallic strip and a stationary electrode. The operating principle is simple, when current is applied, the gas inside ionizes and heats a bimetallic strip which in turn bends toward the stationary electrode thus shorting the starter between the electrodes of the fluorescent lamp After a second the starter's bimetallic strip will cool and open the circuit between the electrodes and the process repeats until the lamp has lit. One disadvantage of glow switch starters is that when the lamp is at the end of its life it will continuously blink on and off until the glow switch starter wears out or an electrode on the fluorescent lamp burns out.
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Diagram of a bimetallic strip showing how the difference in thermal expansion in the two metals leads to a much larger sideways displacement of the strip A bimetallic coil from a thermometer reacts to the heat from a lighter, by uncoiling and then coiling back up when the lighter is removed. A bimetallic strip is used to convert a temperature change into mechanical displacement. 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. The different expansions force the flat strip to bend one way if heated, and in the opposite direction if cooled below its initial temperature.
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The bimetallic strip is usually made from steel and copper. Because these metals expand and contract at different rates. When one of these metals expand it curls tighter, when one contracts it uncurls slightly. When it curls or uncurls, the data is converted into electric signals, which record the temperature change.
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A thermotime switch, or TTS, is a sensor used to control the cold start enrichment process in some older fuel injection systems. An extra injector is placed in the inlet manifold designed to feed all of the cylinders, and whilst the other injectors have flow rates controlled by pulse duration, the cold start injector stays on during the initial cold starting procedure. This duration is controlled by the thermotime switch, which is a bimetallic strip based device placed in the water jacket or in the case of an air-cooled engine, in the engine/timing case. When an engine first starts, the coolant temperature is cold and the bimetallic strip is closed, which in turn supplies the cold start injector with current.
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The engineering world was not to fully understand the properties of springs for such applications for another two centuries. Despite this, it had proved a very valuable experiment as much was learned from its construction. Certainly in this machine Harrison left the world two enduring legacies – the bimetallic strip and the caged roller bearing.
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In electrical switches, including bimetallic strip based thermostats, the switch usually has hysteresis in the switching action. In these cases hysteresis is mechanically achieved via positive feedback within a tipping point mechanism. The positive feedback action minimises the length of time arcing occurs for during the switching and also holds the contacts in an open or closed state.
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A small heater coil is built into the thermotime switch, which effectively gives a timed output to the cold start injector with the timing duration dependent on the temperature of the engine. If the engine is started whilst warm the bimetallic strip remains open due to the higher temperature, meaning the cold start routine is not entered.
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A balance-brake, activated by the position of the fusee, stops the watch half an hour before it is completely run down, in order that the remontoire does not run down also. Temperature compensation is in the form of a 'compensation curb' (or 'Thermometer Kirb' as Harrison called it). This takes the form of a bimetallic strip mounted on the regulating slide, and carrying the curb pins at the free end.
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Thermostat with bimetal coil at (2) In the regulation of heating and cooling, thermostats that operate over a wide range of temperatures are used. In these, one end of the bimetallic strip is mechanically fixed and attached to an electrical power source, while the other (moving) end carries an electrical contact. In adjustable thermostats another contact is positioned with a regulating knob or lever. The position so set controls the regulated temperature, called the set point.
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The original twinkle bulbs were C7½ and some C9¼ incandescent light bulbs with a bimetallic strip. Once the bulb warms up, the strip pulls slightly away from the contact, opening and interrupting the parallel circuit through the bulb and turning it off. The bulb then cools, allowing the strip to bend back and make contact again. This repeats at semi-random intervals ranging from several to less than half a second, and they may appear to speed up and slow down in a "cycle".
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Bimetallic materials are materials that are made out of two different metals or alloys that are tightly bonded together. A good example of a bimetallic material would be a bimetallic strip which is used in some kinds of thermometers. In ISCR, bimetallic materials are small pieces of metals that are coated lightly with a catalyst such as palladium, silver, or platinum. The catalyst drives a faster reaction and the small size of the particles allows them to effectively move into and remain in the target zone.
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Thermal overloads have a small heating device that increases in temperature as the motor running current increases. There are two types of thermal overload relay. In one type, a bimetallic strip located close to a heater deflects as the heater temperature rises until it mechanically causes the device to trip and open the circuit, cutting power to the motor should it become overloaded. A thermal overload will accommodate the brief high starting current of a motor while accurately protecting it from a running current overload.
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Mechanical clock mechanisms are sensitive to temperature changes as each part has tiny tolerance and it leads to errors in time keeping. A bimetallic strip is used to compensate this phenomenon in the mechanism of some timepieces. The most common method is to use a bimetallic construction for the circular rim of the balance wheel. What it does is move a weight in a radial way looking at the circular plane down by the balance wheel, varying then, the momentum of inertia of the balance wheel.
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In 1877, Clover invented an ether inhaler with a water jacket, and by the late 1899 alternatives to ether came to the fore, mainly due to the introduction of spinal anesthesia. Subsequently, this resulted in the decline of ether (1930–1956) use due to the introduction of cyclopropane, trichloroethylene, and halothane. By the 1980s, the anesthetic vaporizer had evolved considerably; subsequent modifications lead to a raft of additional safety features such as temperature compensation, a bimetallic strip, temperature-adjusted splitting ratio and anti-spill measures.
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Thermostats use different types of sensors to measure the temperature. In one form, the mechanical thermostat, a bimetallic strip in the form of a coil directly operates electrical contacts that control the heating or cooling source. Electronic thermostats, instead, use a thermistor or other semiconductor sensor that requires amplification and processing to control the heating or cooling equipment. A thermostat is an example of a "bang-bang controller" as the heating or cooling equipment output is not proportional to the difference between actual temperature and the temperature setpoint.
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There is a plaque dedicated to Harrison on the wall of Summit House, a 1925 modernist office block, on the south side of the square. A memorial tablet to Harrison was unveiled in Westminster Abbey on 24 March 2006, finally recognising him as a worthy companion to his friend George Graham and Thomas Tompion, 'The Father of English Watchmaking', who are both buried in the Abbey. The memorial shows a meridian line (line of constant longitude) in two metals to highlight Harrison's most widespread invention, the bimetallic strip thermometer.
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The balance consisted of a circular steel balance wheel with two bimetallic strips attached diametrically. Each bimetallic strip terminated with a screw thread mounted with a weight or balance nut. The further along the strip this nut was screwed, the greater the compensating effect. Another part of the patent concerned an addition to the form of the balance spring—a coil of smaller radius at each end of the helical spring, which offered increasing resistance to the rotating balance as it turned towards the end of each vibration.
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This process was invented in 2018 by researchers at the University of Stuttgart and Swiss Federal Laboratories for Materials Science and Technology. The self-shaping or self- bending of the wood is enabled by the smart assembly of flat, bi-layered plates where one layer is designed to intentionally shrink or swell with changing moisture but is restricted by the other layer while paralele fiber orientation. This results in extensive "self" shaping analogous to the Bimetallic strip. The shaping can be controlled based on the composition of the bilayer.
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John Harrison's Memorial in Westminster Abbey, London The earliest surviving bimetallic strip was made by the eighteenth-century clockmaker John Harrison who is generally credited with its invention. He made it for his third marine chronometer (H3) of 1759 to compensate for temperature-induced changes in the balance spring. It should not be confused with the bimetallic mechanism for correcting for thermal expansion in his gridiron pendulum. His earliest examples had two individual metal strips joined by rivets but he also invented the later technique of directly fusing molten brass onto a steel substrate.
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The metal with the higher coefficient of thermal expansion is on the outer side of the curve when the strip is heated and on the inner side when cooled. The invention of the bimetallic strip is generally credited to John Harrison, an eighteenth-century clockmaker who made it for his third marine chronometer (H3) of 1759 to compensate for temperature-induced changes in the balance spring. Harrison's invention is recognized in the memorial to him in Westminster Abbey, England. This effect is used in a range of mechanical and electrical devices.
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Saturated vapor pressure for any one agent varies with temperature, and plenum vaporizers are designed to operate within a specific temperature range. They have several features designed to compensate for temperature changes (especially cooling by evaporation). They often have a metal jacket weighing about 5 kg, which equilibrates with the temperature in the room and provides a source of heat. In addition, the entrance to the vaporizing chamber is controlled by a bimetallic strip, which admits more gas to the chamber as it cools, to compensate for the loss of efficiency of evaporation.
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A type of chart recorder, one end of a bi-metallic strip is attached to a long, light metal lever that holds a special pen. Tiny movements of the bimetallic strip cause much larger movements of the free end of the lever and the pen. The pen traces a rising and falling line on a strip of paper attached to a slowly turning drum. The drum usually makes one turn every seven or so days, so afterward each strip of paper contains a complete and accurate record of temperature changes for a whole week.
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Meat thermometers are usually designed to have the probe in the meat during cooking. Some use a bimetallic strip which rotates a needle which shows the temperature on a dial; the whole thermometer can be left inside the oven during cooking. Another variety commonly used on turkey is the pop-up timer, which uses a spring held in by a soft material that "pops up" when the meat reaches a set temperature. Bimetal coil thermometers and pop-up devices are the least reliable types of meat thermometers and should not be trusted as a standalone meat thermometer.
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It was a mahogany box of approximately that housed a movement that, though relatively simple, was close to the same size as Harrison's, with a balance of a similar diameter. The radical difference, however, was a newly designed escapement that featured a horizontally placed pivoted detent that allowed the balance to vibrate freely, except when impulsed by the escape wheel. The spiral balance spring also had a temperature compensation device similar to those in Arnold's watches, and based on Harrison's bimetallic strip of brass and steel. Arnold proposed manufacture of these timekeepers at 60 guineas each.
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Breguet's thermometer, also called a spiral thermometer, is a type of thermometer which uses the expansion of metal under heat to produce a measurement more sensitive, and with a higher range, than both mercury and air thermometers. Working on the principle of a bimetallic strip, it consists of a very slender strip of platinum soldered to a similar strip of silver, with a slip of gold soldered in between. Breguet's thermometer diagram The strips of soldered metals are curved into a helix (a). The upper extremity of the helix is fastened to a metallic support (c) and the lower extremity is connected to an index, which projects over a graduated circle (b).
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Shihlin Electric MCCB with SHT Thermal magnetic circuit breakers, which are the type found in most distribution boards in Europe and countries with a similar wiring arrangements, incorporate both techniques with the electromagnet responding instantaneously to large surges in current (short circuits) and the bimetallic strip responding to less extreme but longer-term over-current conditions. The thermal portion of the circuit breaker provides a time response feature, that trips the circuit breaker sooner for larger over currents but allows smaller overloads to persist for a longer time. This allows short current spikes such as are produced when a motor or other non- resistive load is switched on. With very large over-currents during a short circuit, the magnetic element trips the circuit breaker with no intentional additional delay.
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Two thermal switches Schematic symbol for a thermal overload switch A thermal switch (sometimes thermal reset or thermal cutout (TCO)) is a device which normally opens at a high temperature (often with a faint "plink" sound) and re-closes when the temperature drops. The thermal switch may be a bimetallic strip, often encased in a tubular glass bulb to protect it from dust or short circuit. Another common design uses a bimetallic shallow dome-shaped cap which "clicks" to an inside-out inverted cap shape when heated, such as the "Klixon" brand of thermal cutouts. Alan R. Earls, Robert E. Edwards, Raytheon Company: The First Sixty YearsArcadia Publishing, 2005 , page 9 Unlike a thermal fuse, a thermal switch is usually reusable and is therefore suited to protecting against temporary situations which are common and user-correctable.
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During the late 20th century, flasher bulbs were modified such that the bimetallic strip is a "normally open" switch instead of a "normally closed" one. When first turned on, the strip does not make contact, causing power to flow through the filament until it warms up within a few seconds. It then makes and breaks contact quickly, momentarily allowing a low-resistance path around the filament, causing the bulb (and to a lesser extent the steady bulbs in reaction) to flicker rapidly, much faster than most flasher or twinkle bulbs. These 6-volt bulbs were originally half of the bulbs in a 35-light set, alternated in every other socket with 6-volt steady bulbs (instead of the 3½-volt ones in a normal set of 35), and were sold under the General Electric brand and at Macy's under its own house brand, among others.
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