Hypoxia protection device is a gas heater essential safety device. This article describes the thermocouple to achieve protection in hypoxic gas heater in
Care application functions. The device easy to use, excellent performance, but also reduces the manufacturing cost of a gas heater.
Keywords thermocouple sensor gas heater hypoxia protection

Gas heater is heating equipment for indoor use, requires oxygen consumption at work, in the case of non-ventilated indoor ultra-long working hours can cause hypoxia, cause human discomfort, and even suffocation, endangering personal safety, it is necessary to protect the design of hypoxia . Functional hypoxia protection device is: When low oxygen content measured indoor air control valve will automatically close and alarm display hypoxia markers, reminding the user ventilation. Thermocouple sensor is a common, widely used in temperature measurement. The principle is: to connect the two ends into a closed loop of two different conductors, due to both ends of the temperature range, and thus generate thermoelectric power in the loop. This phenomenon is known as the thermoelectric phenomenon in physics. In this paper, thermocouple thermoelectric phenomena designed a hypoxia protection device.

Works a hypoxia protection device

The protection works: When the gas supply and the oxygen supply is constant, the flame temperature is certain, when sufficient oxygen in the air, the flame temperature can reach 700 ��; when the oxygen content in the air when reduced, the flame temperature is decreased. According to the American standard, in hypoxic state of the flame temperature does not exceed 450 ��, K-type thermocouple thermoelectric power relative temperature at 450 �� for 1815mV. If the thermocouple measured the temperature of the flame of fire often enough, can be identified as the oxygen content in the air is not enough, you need an alarm and close the control valve. Hypoxia protection function of this program is implemented as follows: the use of wide temperature microcontroller AT89C2051, it comes with an internal analog comparator, P110 and P111 are the comparator input pin. The 1815mV potential signal access P111 pin end of the reference voltage signal which requires stable, so pick a regulator device at VCC place. The flame temperature measured by the thermocouple signal after amplification processing access P110 pin, and then use its internal analog comparator compares the two signals. If the signal is below P111 P110 pin pin signal, then the interior of hypoxia, when the control valve is closed and the alarm display. Its circuit diagram shown in Figure

Two hardware components

The device consists of microcontroller, thermocouple, potentiometer components. SCM is the United States launched the efficient microcontroller ATMEL AT89C2051, its own internal analog comparator, P110 and P111 are the comparator input pin. With this analog comparator can achieve hypoxia protection. AT89C2051 instruction and INTEL's MCS - 51 series single-chip fully compatible itself with 2K bytes of flash erasable programmable read-only memory, using this chip can greatly simplify circuit design, but also to achieve the chip heating the other functions, this does not repeat. Thermocouple type K thermocouples use, it receives a signal via the thermoelectric power amplifier after treatment access microcontroller, which also plays a role in the acquisition of thermocouple temperature signals often open fire in the heater. Potential signal potentiometer is 1815mV, its termination of a reference voltage source 358B - 25.

3 Conclusion
The hypoxia protection device running normal gas heater has been tested for two months of continuous work without trouble. Since the sensor uses a thermocouple, the price is lower than other sensors, and the performance is stable, the device has a higher cost.