What are the classification of the resistance thermometer?

Resistance thermometer is divided into four categories, respectively is: 1. Platinum thermal resistance thermometer platinum thermal resistance is characterized by high accuracy, good stability, reliable performance, but in the reducing medium, especially at high temperature of the steam is easy to restore from the oxide is sullied and crisp, and change the relationship between resistance and temperature. In order to overcome the above disadvantages when using core thermal resistance should be in a protective casing. 2. Copper heat resistance thermometer industrial copper heat resistance is commonly used to measure - 5 ℃ ~ 15 ℃ range o + o, the temperature of copper easy purification, is a lot cheaper than platinum, large temperature coefficient of resistance and the relationship is linear, so made a certain resistance of thermal resistance, compared with platinum, if the length of the wire at the same time, the copper wire is very thin, lower mechanical strength, if the same wire diameter, length, many times, volume increase. In addition, the copper in 1 oo ℃ or more easy oxidation, corrosion resistance and poor, so the working temperature is not more than 15 ℃. 3. Nickel heat resistance thermometer nickel heat resistance temperature coefficient is big, the sensitivity is higher than platinum and copper, are commonly used to measure - 6 ℃ ~ + 18 o o ℃ temperature range. Due to the complicated manufacturing process of nickel heat resistance, it is hard to get the same nickel wire alpha, so its measuring accuracy is lower than the platinum thermal resistance, the standardization of China's current regulations have ni100 thermal resistance index number, ni300, ni500. 4. Semiconductor thermistor thermometer semiconductor point thermometer is the use of metals such as manganese, nickel, copper and iron oxide mixture of the thermal resistor as temperature measuring element, its usu shape, round shape, washer and chip, commonly used type 61 bead and micro bead thermistors semiconductor. And the general thermal resistance is different is that it is the negative temperature coefficient of resistance, temperature, resistance is reduced, change is big, temperature coefficient of resistance of alpha da 2 ~ - 7 [ ( %) ] 10 to 100 times larger, more metal thermal resistance, therefore, can use lower display instrument accuracy.