Thermocouple used in gas heaters

Gas heater is indoor use of heating equipment, work need oxygen consumption, without ventilation of working long hours can cause indoor oxygen, cause human body unwell, suffocation, even endanger personal safety, so there must be a lack of oxygen protection design. Hypoxia is the function of protection device: when the system of oxygen on the low side will automatically shut down when measured indoor air control valve, and alarm display of oxygen, remind consumer ventilated take a breath.

thermocouple sensor is a common, widely used in the temperature measurement. Its principle is: will the ends of the two different conductor into a closed loop, because the two end temperature range, thus produce thermoelectric potential in the loop. This phenomenon is called thermoelectric phenomena in physics. In this paper, using the thermocouple thermoelectric phenomena an anoxic protection device is designed.

1, the working principle of the oxygen protective device to protect the working principle is: when the gas supply and oxygen flame combustion temperature is also a certain, when sufficient oxygen in the air, the flame temperature can reach 700 ℃ or so; When oxygen levels fall in the air, the flame temperature is lower. According to American standard, the oxygen flame temperature does not exceed 450 ℃, K type thermocouple in the relative temperature 450 ℃ when the thermoelectric potential of 1815 mv. If the thermocouple measured often open flame temperature is not enough, can be regarded as not enough oxygen in the air, need to report to the police and close the valve. Hypoxia protection function of this scheme is that: the wide temperature type single-chip microcomputer AT89C2051, it itself an analog comparator, P110 and P111 are the comparator input pin. Potential of 1815 mv signal access P111 pin, which requires stable reference voltage signal, so after a voltage stabilizer at VCC. The flame temperature measured in the thermocouple signal after amplification treatment access P110 tube feet, then use its internal analog comparator compares the two electrical signals. If the P110 pin signals below P111 tube feet, then indoor oxygen, then control valve closed, and alarm display.

2, hardware composition, the device is mainly composed of single chip microcomputer, thermocouple, potentiometer. MCU USES is the ATMEL company launched efficient SCM AT89C2051, it itself analog comparator, P110 and P111 are the comparator input pin. Using the analog comparator anoxic protection function can be realized. AT89C2051 instruction and INTEL MCS - 51 series microcontroller is fully compatible with, itself with 2 k byte flash programmable can erase the read only memory (ROM), using this chip can be greatly simplified the design of the circuit, using the chip but also realize the function of other heaters, don't go into here. Thermocouple with K type thermocouple, it receives the thermoelectric potential by the amplifier amplification signal processing after the access to the single chip microcomputer, the thermocouple in the heater also to play the role of a acquisition often flame temperature signal. Potentiometer voltage signal is 1815 mv, its reference termination 358 b - a voltage source 25.

3, conclusion the oxygen protective device in the gas heater running normally, after two months of continuous work trouble-free. The adoption of thermocouple sensor, low prices than other sensors, and the performance is stable, the device has high cost performance.

related knowledge:

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