When selecting the thermistor for temperature measurement, please select according to the following items
1. Purpose
Temperature measurement, temperature recording, temperature control, temperature compensation, other ——
2. Use environment
In the atmosphere, in the water, in the sea, in the steam, in the acid-alkaline mist, and others——
3. Reliability test items
Cold and heat exchange, steam resistance, water resistance, vibration resistance, heat resistance, cold resistance and other test conditions
4. Operating temperature range ——℃～——℃
5. Shape, product name and size
6. Resistance value ——KQ±——%, at——℃
7. B value (please choose according to this product introduction)
B(——℃／——℃)=——K±——%
8. Thermal time constant ——seconds～——seconds,——environment
9. Product code description
A thermistor code description:
①Representative: Changzhou Kewen Sensor Material Co., Ltd.
②Representative: NTC thermistor
③Represents the resistance package type: G: single-ended glass seal; D: axial glass seal type; E: epoxy resin package type; Q: enameled wire type;
④ Representative B value 25/50℃: 3470K
⑤Represent the allowable deviation code of B value: F is ±1%; G is ±2%; H is ±3%; J is ±5%
⑥Represents the nominal resistance value R25: 103 is 10KΩ
⑦Representing the allowable deviation code of resistance value: F is ±1%; G is ±2%; H is ±3%: J is ±5%
B sensor code description:
①Representative: Changzhou Kewen Sensor Material Co., Ltd.
②Representative: Sensor
③Representative: Sensor type: T: Metal shell type; S: Plastic shell type; E: Epoxy resin encapsulation type; Q: All-round type: C: Special type for washing machine; R: Special type for water heater; F: Special type for refrigerator: N: floor heating container and refrigerated truck special type: B: surface mounting type: D: special type for soybean milk machine; Y: liquid level sensor:
④Representative: customer number;
⑤Representative: drawing number.
Precautions for selection
1. Although the thermistor can withstand the thermal shock from room temperature to 200℃, because its packaging material is glass, at the same time, in order to prevent the thermal semiconductor from aging as much as possible, rapid temperature changes should be avoided as much as possible.
2. The current flowing through the thermistor will cause the component to heat up and produce a temperature difference, so please consider this factor before selecting. (When the self-heating value of the component is 1/10 of the heat dissipation coefficient δ [Mw/℃], the temperature difference is 0.1℃;
When δ is 1/100, the temperature difference is 0.01℃)
3. Due to poor insulation and electrostatic induction of the used circuit, and wrong wiring will cause excessive current flowing through the thermistor to damage the thermistor, you must pay attention to the wiring method so that no overcurrent flows through the thermistor.
4. After 5T (seconds), the measurement will start after more than 7T (seconds).
5. When used in systems that require high precision or do not want the resistance of thermal semiconductors to have aging, use high-reliability thermal semiconductors that have been certified by high-temperature tests. The circular (capable of passing large current) thermistor, which is often used for circuit temperature compensation, cannot be used in a system that allows its characteristics to vary from year to year. It is not manufactured as a temperature measurement component, so avoid using it in In the system that requires high reliability and the meter that requires high-precision measurement.
6. When inserting into the protective tube, in order to prevent thermal leakage temperature error, when using a metal protective tube, it should be inserted more than 25 times the depth of the pipe diameter, and when using a non-metal protective tube, it should be inserted more than 15 times the depth.
7. If there are water droplets, dust or ionic compounds generated by condensation between the leads and on the surface of the insulator, the apparent resistance will drop or become unstable and cause measurement errors. Therefore, moisture-proof and insulating treatments should be carried out to maintain It's dry.
