Abstract: infrared thermometer temperature measurement using infrared temperature sensor, the use of GE’s zTP135S-R thermopile infrared temperature sensor signals the non-contact temperature measurement. Described in detail ZTP135S-R sensor working principle and performance. It comes with ADC, 8-bit microcontroller megal6 connected together to achieve the function of the thermometer.
Keywords: Thermopile Temperature Sensor; ZTPl35S-R; AVR microcontroller; temperature; Application
Now, people of their physical health very closely. We all like to have a good body. Human body temperature is one of the important physiological parameters, its monitoring is very important. Thermometer on the market is the most popular electronic thermometer, especially non-contact infrared thermometer. At present, the development of infrared thermometers are developed by Huazhong University of Science and Technology "eye: HW a 05" body temperature infrared thermal imager. The resolution up to 0.06 ?; CAS Shanghai Research Institute of Physics, Lanzhou University, infrared thermometer and hua technology development center developed LHW-I-type infrared thermometer. Bo Lang, the German foreign products developed by the Group only 1 second to measure the body temperature of the infrared thermometer; Omron developed several non-contact infrared thermometer and BJ40 Medical Non-contact infrared thermometers (accuracy ± tO.2 ?, the main device is the infrared temperature sensor. This paper presents the application of GE’s ZTP135S-R infrared temperature sensor of the thermometer design.
2 Principles of infrared temperature sensor
Temperature above absolute zero all of nature (-273.15 ?) objects. Since molecules are in constant thermal motion to the surrounding space, including infrared radiation, including electromagnetic waves. The radiation energy density and the temperature of relations is the object itself, Planck (Plank) law. Principles of infrared temperature measurement is the same, are based on Planck principle. General understanding of the infrared temperature measurement of an object. In fact, measurement is the target object and the sensor or is the difference between the ambient temperature. The size of the object directly with radiant energy of the object temperature. Specifically, is the thermodynamic temperature of the object is proportional to the 4 th power. With the formula can be expressed as:
E = de (T4-T4o) (1)
Where, E is the degree of radiation emitted. Unit is W/m3;
Stephen d is a Boltzmann constant, 5.67×10-8W / (m2 · K4);
d is the object of the radiation rate:
T is the temperature of an object (K);
To is the ambient temperature around an object (K).
Radiation wavelength of the main body 9 µm-10 µm in the infrared. Through the body’s own infrared energy radiated will be able to measure accurately measuring the surface temperature of the body. Since the wavelength range of light absorbed by the air is not, and therefore can use the infrared radiation energy of the human body to accurately measure the body surface temperature.
Principles of infrared temperature sensor using thermocouples to measure the target object and the sensor or the difference between the ambient temperature. Thermocouple principle is two different metals A and B form a closed loop, when the two contacts at the same time end temperature (T> To), thermoelectric power generation circuit Eab, where T is called the hot end, the working end or measuring end, To is called the cold end of the free end or the reference junction. A and B as hot electrode. The size of thermoelectric power by the contact potential (also known as Burr posted potential) and thermoelectric power (also known as Thomson potential) decision.
3 ZTPl35S-R and performance of works
GE produced ZTP135S-R is an infrared temperature sensor specifically for non-contact temperature measurement devices, and its main parameters are as follows:
Chip size: 1.8 mmxl.8 mm;
Light hole size: 1.4 mm x 1.4 mm;
Even power: 60 to:
Active area: O.7 mmx0.7 ram;
Resistance: 60 kn ± 30%;
Temperature Coefficient of Resistance: <0.12% / ?;
Sensitivity: 65 V / W ± 30%;
Noise voltage: 32 nVrms (typical);
Detection sensitivity: 1.4E08 emHz (1 / 2) W (typical);
Time factor: 25 ms (typical);
Heating reactor for temperature compensation: R = 100 kO, temperature is 25 ? (R tolerance of ± 3%), ß = 3960 (ß tolerance of ± 0.5%);
Package Type: TO-46;
Operating temperature: -20 ? ~ 100 ?;
Storage temperature: -40 ? ~ 120 ?.
Its shape and pin arrangement shown in Figure 1.
The radiation measured object through the window and aperture focus on the receiving device (thermopile) and on-chip heat, heat 60 series on-chip thermocouple. Each thermocouple in the hot end of heat around the center of the film into a ring, welded together, you can get from all the leads of the thermoelectric power of the galvanic and. This design has a smaller thermal inertia and high sensitivity. Sensor uses a negative temperature coefficient thermistor for temperature compensation.
Figures 2, 3 and 4, respectively, shows the curve of the sensitivity of the sensor, the resistance change rate curve and the transmission waveform.
4 Application of infrared sensors
This design uses AVR microcontroller for digital signal processing, it z1 "P135S-R connected to the temperature of their electrical signals collected for processing. And then after filtering and amplification, the temperature of the standard were extracted from the MD signal conversion and, ultimately, LCD Monitor (LMD) on the display. LCD’s 8 data lines connected. PB mouth; control lines RS, R / W, EN respectively, then PD0, PDl, PD3; LCD backlight control by the PD4. buzzer by the PD5 control. infrared temperature signal PA0 microcontroller port connected, ambient temperature compensation signal microcontroller PAI access port. which also designed the two buttons (keyl, key2), keyl for the system control switch, key2 to reset the switch. Figure 5 shows megal6 MCU peripheral circuits.
In the temperature measurement system, the temperature sensor is an important device, its performance directly affects temperature measurement accuracy. Need to choose different measurement precision sensors for infrared temperature sensors, because it is non-contact, so particularly high demands on the environment, the use of thermocouple measurement principle, to compensate for ambient temperature, to obtain accurate measurement results. This design uses ZTPl35S-R sensors satisfy the requirements. Linear measure temperature changes, and. The device’s infrared sensor used in the body only absorbs infrared radiation to the human body without any radiation emission. It uses a passive and non-contact measurement. Does not harm the human body radiation.