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Main form and type of temperature sensor

First, the temperature sensor three main forms of thermocouple, platinum resistance and thermal resistance.

1.The thermocouple consists of two different wires welded together, for example: NiCr-Ni (K type), the use of thermoelectric effect to work, two different wires, forming a closed loop, the existence of two different conductors With temperature difference, both produce electric heat. Thus forming a loop in the current, this phenomenon is called thermoelectric phenomenon.

2.Platinum resistance measurement principle is different from the thermocouple measurement method. Platinum resistance sensor is essentially a kind of PTC thermistor. Metal resistivity increases with increasing temperature, so this property is used to measure temperature. Thin-film platinum resistance, due to the thin structure, so the resistance is not affected under the premise of the provision of a glass casing for protection. The current general resistance of platinum resistance 100Ohm (0 ℃), which is the current international common platinum resistance. Another PT100 sensor using winding ceramic, this method will be platinum wire attack into a spiral, and then into the ceramic matrix, the sensor structure is very close, in all platinum resistance sensor, the highest accuracy of this structure, the use of time Long lasting and without aging, but compared to the thermocouple measurement principle, the reaction time is slow, so often used in food science and technology in the application, especially in the laboratory research and development.

3. NTC thermistor using a more extensive and more economical one temperature sensor. Due to the mixed oxide ceramic material, it has a negative temperature coefficient, which is why it is called NTC (negative temperature coefficient abbreviation). As temperature increases, the resistance decreases, which is exactly the opposite of the PT100 sensor's measurement characteristics.

Second, through the temperature sensor temperature probe type also has three main:

1. Piercing / immersion probe: used to measure the temperature of liquids and solids, the probe is designed to needle-shaped piercing the front end. If the temperature of the measuring probe is lower than that of the measured object during use, the heat energy will be guided from the measured object to the probe according to the principle of energy conservation. If the temperature of the measuring probe is higher than the measured object, the heat energy is transmitted from the probe to measured objects. This means that the measured object is warmed up and the measured temperature is the temperature of the object after it is heated. In this measurement, the ratio of the probe to the medium must be taken into consideration because the better the ratio of the probe to the medium, the more accurate of the measured object to obtain the energy, due to the energy transfer causes measurement error. It is important to note that instead of the temperature of the medium measured by the instrument, the temperature of the sensor, the measurement error can be reduced by inserting 10 or 15 times the depth of the probe into the probe, or when measuring the fluid holding liquid flow can effectively reduce the error.

2. Air temperature probe, used to measure the air temperature, such as cold storage, freezer, air-conditioned room (thermostat), Ventilation (ventilation / exhaust), etc., the air probe sensor is exposed. The best solution is in the air flow of 2-3m / s, the downstream light shift probe, the temperature reached a balance of stability.

3. Surface probe, used to measure the surface temperature of the object. Air temperature probe and surface probe When using the surface temperature measurement, the front of the probe must be perpendicular to the measured object, fully and in full contact with the measured object. It must be noted that the probe and the measured object's contact surface must be flat, otherwise it will affect the measurement results.

4. The temperature probe using contact methods, mainly used in food sampling, temperature monitoring during food transport, flue gas flow in the center of the temperature measurement, temperature measurement at different points, electronic welding surface temperature measurement to detect preheating conditions. The temperature of the chemical solution is measured by immersion in the chemical reaction process, in the machinery manufacturing industry, by measuring the surface temperature of bearings and gears, for maintenance and overhaul, and so on.