In everyday life around a person, conductors, insulators, electronics function using a different approach. Let's try to look inside, lift the curtain. At the same time, we note what a thermocouple is for a gas stove, why it is needed. In skilled hands come in handy.
Gas Stoves
A modern gas stove is a complicated device, but it’s a pleasure to use the unit. Most products are equipped with electric ignition, so get ready to connect to the outlet, like other household kitchen appliances. The principle of operation of ignition is the accumulation of charge by the capacitor, followed by discharge through the key element after the voltage reaches a fixed value. Voltage with an amplitude of 2-3 kV pierces a discharger located in the burner, an electric arc arises, igniting the gas. The blue fuel valve opens simultaneously with the process described above. Discharge occurs instantly.
Electrical ignition is present only on the burners. Sometimes, to automate the oven, it is necessary either to lay additional conductors according to the instructions, or to completely modify the design. As soon as the automation reached such heights that the gas stove ignites itself, it is not surprising that the designers supplied the equipment with protection against the extinction of fire. The simplest example is when gas disappears in network communications, then it is served again. And without warning from the utilities.
The owner finds a kitchen filled with a specific, pungent smell. The explosion is far away, and the water from the kettle will have to be poured into the sink, for fear of poisoning. Some products are gaining odors, it will be impossible to eat spoiled by the scent.
The presence of a gas stove thermocouple helps to avoid such excesses. If you inspect the burner, removing the reflector, the divider, we note two things:
- Candle, resembling a car.
- Thermocouple.
The first is responsible for the ignition of the flame, the second controls that the fire burns properly. Honestly, I did not have to see the models that give a spark when re-supplying gas, done for safety( if the concentration reaches an explosive one, the kitchen will jerk).The current level of technology simply does not provide a 100% guarantee of the correct operation of the structure. If there is enough gas in the kitchen, a fire is guaranteed. In practice, a pair of analyzers outside, a turbine speed sensor in the pipeline would correct the situation, but who wants to risk it. Automation can 3-4 times try to light a damped fire.
Due to the reasons described, the thermocouple detects the extinction of the flame, the path of supply of blue fuel to the gas stove is closed. The oven is not always equipped with electric ignition and protection against flame extinction. It is important to track supplied options. We have a chance to fill the kitchen with a portion of gas, if there is no protection against the extinction of the flame. Ask the consultant where the thermocouples are located. Then, in order to avoid human error, verify the words with the manual on the gas stove. It is better to spend an extra quarter of an hour, having done these operations, than to endanger life.
A typical ignition device( a block inside a gas stove) is supplied with six or four pairs of contacts. Each is capable of producing a spark. Professional slang is described in words: the outputs are connected in parallel. Always re-equip the gas stove. On the counter there are models where a special scheme shows the route of laying the conductors that complement the oven with electric ignition. Similar procedures can be done with burning control, equipping the selected area with a thermocouple. To introduce another element, will not be difficult for an experienced technician.
Physical basis of the thermocouple operation of the
. Seebeck discovered a curious effect by taking two pieces of wire of dissimilar conductors: soldered, the connection was heated, the circuit formed an EMF, current flowed.
What is the diversity? A close study of the issue reveals: if the conductor is heated from one end, the opposite is left at room temperature, EMF occurs in the wire. The value is a different sign. Scientists explain the change in energy levels of particles that transfer charge. As a result, electrons rush from the heated part of the conductor to the cold part or vice versa, forming an emf of a positive / negative sign.
What determines the direction of movement of charge carriers. Defined by the physical features of the conductor. For each material, the thermopower value was entered, the figure is positive or negative. In pure iron, the parameter is +15 μV / ºС, in nickel - 20.8 μV / ºС.Now a few words about the appointment of a thermocouple.
Thermocouple
According to the definition of an international standard, a thermocouple is represented by two connected conductors used as part of a temperature measuring device. It remains to add: the material of the wires is selected by a different sign of the thermopower coefficients. Maximum potential difference is achieved. Measurement accuracy is directly determined by the value of the measured parameter. Since the devices demonstrate absolute, relative errors.
A common thermocouple is considered to be an alumel product( - 17.3 µV / ºС), chromel( + 24 µV / ºС).At a junction temperature of 300 ºС, the product outputs a voltage of 12 mV to the contacts. The digital meter estimates the value according to the obtained result, the gas stove performs the necessary operations. In the simplest case, a thermocouple determines the presence of fire burners. The fire goes out - the safety valve is activated, shutting off the gas supply. The concept of safe use of stove is implemented.
Sometimes an accurate temperature measurement is not required, the circuit is organized on a digital comparator that compares the voltage of the thermocouple with a given level. The threshold is crossed - the circuit is triggered. Further actions of the gas stove are determined by the algorithm laid down by the developers.
Thermocouples are used in household appliances due to unparalleled reliability, low cost, fault tolerance. Indeed, as an ordinary wire can break. Will break - not for long to grow up. The place of the soldering is restored easily. Gas stove with a thermocouple works reliably, maintainability.
The unification aspect plays a significant role. The thermocouple alumel-chromel is easily replaced by another similar one. Alloys are easy to purchase separately, you can make a temperature meter for a gas stove with your own hands. An important criterion for the marketing appeal of equipment.
Seeing simplicity, the buyer is willing to spend money. Installation is simple. To lay a pair of wires under the force of each. A few words about the appointment of a thermocouple.
Application of thermocouple
Thermocouple wiring is placed in the screen to avoid interference, interference. The step will allow to exclude false alarms of the equipment, incorrect measurements. Additionally, twisting the wires with each other will help to avoid interference. The stability of computer twisted pairs is based on a similar principle.
The voltage at the output of the sensor depends on the temperature difference between the cold and the hot end. Therefore, in the exact mechanisms, it is necessary to additionally evaluate the parameters of the environment in the place of reading. In home appliances, gas stoves, the nuances are missing as unnecessary.
Thermocouple is located near the candle. The temperature control factor is radiation. The fire does not touch the element, the heat reaches the sensor. Since the extinction of the burners occurs separately, according to science, the output of each thermocouple is fed to its own measuring device. In practice, a mounting or schematic combination of a logical "and-not."If one signal disappears, an alarm pulse is immediately generated, which is used as intended. We monitor that all the burners plus the oven work.
Replacing parts
Before replacing the thermocouple, try cleaning it. A symptom of a malfunction is:
- button is pressed;
- lights up the flame;
- fire is on while your finger is on the button.
It is necessary to remove the hand, the flame disappears. It should be cleaned with a sandpaper sensor head located under the divider. If the action is helpless, the thermocouple of the gas stove is replaced. The solenoid valve is designed to operate when the voltage reaches a certain level. If you can not get the original part, remember the fact. The threshold of operation can be found in the technical parameters of the solenoid valve. Of course, after the assembly, the system should be checked for operability.
Note a little-known fact: the type of nozzle is determined by the gas pressure of the pipeline. Consider the transition from natural gas( methane) to bottled. The latter pressure is higher, the diameter of the nozzle already. Where to get the product to replace the old. The gas stove is equipped with two sets of nozzles. The manufacturer considers the possibility of switching to a new type of fuel. A special allen key is included in the package for the replacement.
