Temperature sensor material properties
At present, the most cost-effective solution is to use the NTC (Negative Temperature Coefficient) thermistor at a cost-effective price. The NTC class device is a simple solution that consumes very little power, has very good accuracy over a wide temperature range, and reacts quickly to temperature changes. From the engineer's point of view, these various specifications of the device for electrical and structural design provides a very high flexibility. NTC thermistor
The most basic design and specification parameters of the NTC device are resistance values (typically values at 25 ° C) and tolerances. However, it must be remembered that the working principle of the thermistor is closely related to the temperature. Therefore, the engineer should ensure that the designed product can be used normally when the operating temperature reaches the limit. In high temperature (low impedance) environments, the resistance value must be high enough to reduce system errors such as contact resistance and interconnect resistance. On the contrary, in the low temperature (high impedance) environment, if the current through the thermistor is not large enough, the sensitivity will drop.
Tolerances are usually expressed in ° C and can be used as a measure of temperature accuracy of the device. In a few cases, the manufacturer gives the tolerance expressed as a resistance value, that is, the proximity of the device resistance to its expected resistance at a given temperature. For detailed speculators and purchasers, it is important to remember that the tolerance requirements for a particular design can be limited to a specific temperature or to a slightly wider temperature range. In the second case, the tolerance itself will vary with the device's absolute resistance value. The designer needs to use the negative temperature coefficient specified for the device to calculate the tolerance across the temperature range to ensure that the selected components meet the system's measurement accuracy requirements.
In the operating temperature range, the performance of the device depends on its own material and structure, and by the third type of basic specifications, that is, the device R-T curve to describe. When ordering NTC devices, designers often specify only resistors, tolerances, and standard curves. However, in many cases other parameters are the key to ensuring that the system works as expected. One of the most important parameters is the value of b, which indicates the sensitivity of the device to temperature changes, and equally important is the calibration tolerance of the parameter. Vishay's devices offer very good b-values and tolerances, resulting in higher accuracy and better overall system reliability, and are well-behaved over the device's entire operating temperature range.
The resistance of the conductor changes with the temperature changes, by measuring its resistance to calculate the temperature of the measured object, the use of this principle temperature sensors into the sensor is the resistance temperature sensor, this sensor is mainly used for -200-500 ℃ temperature range Within the temperature measurement. Pure metal is the main manufacturing material of thermal resistance, the thermal resistance of the material should have the following characteristics:
① resistance temperature coefficient should be large and stable, resistance and temperature should have a good linear relationship between. The following are the same as the "
② high resistivity, heat capacity is small, the reaction speed is fast. The following are the same as the "
③ material reproducibility and process is good, low prices. Thermistor temperature characteristics
④ in the temperature range of chemical and physical properties of stability. The following are the same as the "
At present, the most widely used in the industry of platinum and copper, and has been made Standard thermal resistance test.