Selection reference

Selection reference:
1, the choice of long life, strong adaptability of the original, the overall sintering of the outer wire wound ceramic platinum resistance is a better choice.
2. Accuracy and temperature measurement range of components:
According to the actual requirements of the site, the temperature range is too large, the processing difficulty increases the waste cost.
● Grade B: (0.30 0.005 ︰ T ︰) ℃, temperature range:-200 ℃ ~ 700 ℃
● Grade A: (0.15 0.002 ︰ T ︰) ℃, temperature range:-150 ℃ ~ 650 ℃
● Class 1/3B: 1/3(0.30 0.005 ︰ T ︰) ℃, temperature range:-100 ℃ ~ 400 ℃
● Class 1/5B: 1/5(0.30 0.005 ︰ T ︰) ℃, temperature range:-60 ℃ ~ 650 ℃
● 1/10B grade: 1/10(0.30 0.005 ︰ t ︰) ℃, temperature range:-60 ℃ ~ 500 ℃
● To obtain an accuracy higher than class 1/10B, a secondary instrument with non-linearization correction must be provided. Can choose thermal resistance "zero temperature drift" high precision intelligent integrated temperature transmitter RS485 output type or JWT4100Z, temperature range, accuracy level is higher than 1/10B level.
● If you want to make high-precision measurements in a wider range, the sensor must use a thermocouple. Thermocouple "zero temperature drift" high precision intelligent integrated temperature transmitter RS485 output type or JWT4100R is a better choice (see 9.1)
3. Structure form and material selection
At present, instruments and equipment are becoming more and more economical and miniature, and temperature measuring probes are required to be relatively small, such as φ2.5, φ3, φ3.5,
φ4, φ5, φ6, etc., generally according to the user drawings and technical requirements (accuracy, temperature range, lead type, response speed, pressure, environmental medium type, sealing, etc.) to improve the next design, the two sides reached a consensus after the implementation.
4. The leads of temperature measuring elements with 1/5B and 1/10B precision shall be single and four wires below 0.12mm2, without shielding as much as possible to reduce thermal conductivity error.
5, the probe size has an impact on the accuracy of measuring temperature
(1) Precision temperature measurement: Some users require Pt100 to have very precise accuracy, such as 1/5B and 1/10B. According to experience, 1/3B Φ 3 protection tube needs to have a length of more than 50mm; 1/5B Φ 3 protection tube needs to have a length of more than 100mm; 1/10B Φ 3 protection tube needs to have a length of more than 150mm; Otherwise, no matter how accurate the probe is, due to heat conduction, the inner cavity of the protective tube is lower than the temperature of the outer surface of the protective tube due to the heat conduction of the wire, which makes the originally qualified components exceed the difference in the field measurement (it is difficult to find in actual use, only known by simulation experiments). What if the installation space is not allowed to be so long? Use micro-thermocouple type "zero temperature drift" high-precision intelligent integrated temperature transmitter, such as φ1mm, φ1.5 and φ2 probes to make spring-like.
(2) When the insertion depth is small, the pressure is large, the medium flow rate is relatively high, and the diameter of the probe protection tube is required to be relatively large: the wall thickness is relatively thick, such as Φ φ12 × 2 protection tube, the insertion depth is 70mm, grade A platinum resistor is installed, and the measured temperature is around 150 ℃. Simulating the experimental results, its "measured temperature" is higher than the actual temperature (-5 ℃), in the measurement institute, such problems often occur when the core is pulled out for inspection, which does not represent the actual situation even if the original is qualified. In order to solve such problems, the company has successfully developed a "temperature measuring element capable of realizing precision measurement of small insertion depth" through scientific research and has obtained the invention patent "ZL 2018 1 0053898.7", which has solved the problems in this respect. It is used to measure the surface temperature of the outer end surface of the sensor protection tube to realize the measurement of the medium, and the response speed is fast.
(3) high temperature surface temperature measurement: for example, the vehicle-mounted magnesium hydride storage and transportation tank is filled with magnesium hydroxide in a container set on the surface of the heater. when the heater is heated to 200~300 ℃, the magnesium hydroxide releases hydrogen. the heater needs more accurate surface temperature measurement, which uses the extended surface temperature measurement scheme of the invention patent "ZL 2018 1 0053898.7. In Dalian, a relatively successful home.
6. Response time: the thinner the protective tube, the thinner the tube wall, the faster the response.
7. Platinum resistance and thermocouple can be calibrated and corrected together with transmitter to achieve higher precision output and remote transmission.
8. Thermocouple realizes high-precision output and remote transmission of higher temperature by calibration and correction together with transmitter.

Accuracy and Error List (Reference)