便于國外顧客朋友更精準、高效選用生產(chǎn)的NTC熱敏電阻、溫度傳感器產(chǎn)品，現(xiàn)推出負溫度系數(shù)NTC熱敏電阻在應用選型時必須注意的事項和溫度測量的選擇標準表
Application Notes of NTC thermistors
How to order
Selection criteria for temperature measurement are
1. Purpose
Temperature measurement, temperature record, temperature control, temperature compensation, and so on
2. Environment
In air, in water, in the sea water, humid air, acid or basic atmosphere, and so on
3. Reliability test
Heating-cooling cycle, heat shock, wet resistance, heat resistance, cold resistance, and so on
4. temperature range
_____________℃ ~ ___________________ ℃
5. shape, model and dimensions
_____________________________________________
6. Resistance range
_________ KW ± ______ % at ______ ℃
7. B value (selection according to this product catalog)
B (_℃/__℃) = ___ K ± ___ %
8. Thermal time constant
_____ S ~ ______ S in _________ (environment)
Options
1. tube or case can be added on request
2. connecting termination can be machined
3. manufacture to meet special request (for parameters, shape)
Selection notes
1. Although thermistor can resistant to heat shock in the cycle of room temperature to 200℃, any sharp change in temperature still should be avoid as the sealing material is glass and ageing in ceramic semiconductor may occur.
2. The current flowing through thermistor leads to error in temperature due to self heating of the element. The error is about 0.1℃ when self heat of the element is 1/10 of dissipation factor, and 0.01℃ for 1/100.
3. Because of insulation failure in electric circuit and electrostatic induction, wrong wire connection could damage the thermistor due to too much current flowing through the ceramic semiconductor. Wire connection must be sure that no over current passes through the element.
4. It is better to start the measurement after 7 times, at least 5 times thermal time constant.
5. When used in the system where high accuracy is required or the ageing is not expected in ceramic semiconductor, a high reliable thermistor semiconductor should be applied which has been certificated by test at high temperature.
6. In the case of metal tube protection, the deepness of inserting should be greater than 25 times of tube diameter in order to avoid error due to heat leakage. In the case of nonmetal tube, the deepness should be greater than 15 time of the diameter.
7. Water drops, dust layer or ionic compounds formed between leads and on the surface of insulations can lead to decrease or being unstable in appearance resistance. This then leads to a measurement error. Therefore, the elements should be kept in dry conditions by taking such measures as wet protection, insulation etc..
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