This standard specifies the verification items and technical requirements of low temperature test chambers, verification instruments, verification methods, verification results and treatment. JB/T 4278.8-1993 Verification methods for rubber and plastic wire and cable test equipment Low temperature test chamber JB/T4278.8-1993 Standard download decompression password: www.bzxz.net

Mechanical Industry Standard of the People's Republic of China
JB/T4278.8-1993
Verification Method of Rubber and Plastic Wire and Cable Test Instruments and Equipment Low Temperature Test Chamber
Published on August 21, 1993
Ministry of Machinery Industry of the People's Republic of China
Implementation on October 1, 1993
Mechanical Industry Standard of the People's Republic of Chinabzxz.net
Verification Method of Rubber and Plastic Wire and Cable Test Instruments and Equipment Low Temperature Test Chamber
1 Subject Content and Scope of Application
JB/T4278.81993
Replaces JB4278.8-1986
This standard specifies the verification items and technical requirements, verification instruments, calculation of temperature deviation and verification results and processing of low temperature test chambers. This standard applies to the verification of the working space of low temperature test chambers for wires and cables. Reference standards
JB/T4278.1 General principles for the verification method of rubber and plastic wire and cable test equipment
3 Verification items and technical requirements
The temperature deviation of the working space of the test box shall comply with the provisions of the temperature deviation in the relevant standards for the test method of wire continuity. Verification instruments
Thermocouples with a wire diameter of 0.5mm and a node diameter of not more than 2.0mm, nickel-chromium-copper-nickel (Constantan), nickel-chromium-nickel silicon or other 4.1
material thermocouples.
4.2 The actual measurement deviation of the DC digital voltmeter is less than 0.05%. When using nickel-chromium-copper-nickel (Constantan) thermocouples, the resolution of the digital voltmeter shall not be less than 10μV; when using other thermocouples, the resolution of the digital voltmeter shall not be less than 1uV. 4.3 Thermocouple conversion switch,
4.4 The meter graduation value is 0.1°.
4.5 Ice bottle.
5 Verification method
5.1 The working space is called the measured space during the verification process. The measured space is located near the center of the test chamber, and its interface is parallel to the interface of the space inside the chamber. The measured space cannot be smaller than the space occupied by the sample, and the center of the space should not deviate from the temperature sensing end of the thermometer indicating the test temperature of the test chamber by 25mm.
5.2 Use 9 thermocouples to measure the temperature of 9 measuring points in the measured space, one measuring point is the center point of the measured space, and the other 8 measuring points are the 8 vertices of the measured space. The length of the thermocouple at each measuring point in the test chamber is not less than 300mm. Note: All thermocouples should be calibrated. The 9 thermocouples should be composed of the same spool of wires so that the difference in their mutual potential below 200℃ is converted into a temperature difference of no more than 0.2℃
Adjust the temperature of the test chamber so that the temperature of the test chamber does not deviate from the test requirement temperature by ±2℃. 5.3
5.4 Start measuring 1 hour after the temperature of the test chamber stabilizes. Quickly record the thermoelectric potential of the thermocouples at the 9 measuring points, measure once every 5 minutes (0, 5, 10, 15, 20 minutes), complete 5 measurements, and calculate the temperature deviation
6.1 Calculate the spatial temperature deviation
Calculate the average value of the thermoelectric potential of the 5 measured values ​​of the 9 measuring points respectively, and convert it to the average temperature of each measuring point by looking up the graduation table. Approved by the Ministry of Machinery Industry on August 21, 1993
Implementation on October 1, 1993
JB/T4278.81993
Based on the average temperature of the center point of the measured space, calculate the spatial temperature deviation (accurate to 0.1°C) between the average temperature of each measuring point and the average temperature of the center point according to the following formula.
aj=t,-t,
wherein, a;—spatial temperature deviation of the ith vertex of the measured space, i=1~8, ℃; t;—-average temperature of the ith item point of the measured space, i=1~8, C; t. ——average temperature of the center point of the measured space, ℃. 6.2 Calculation of time temperature fluctuation
Calculate the difference between the highest temperature and the lowest temperature of the 8 vertices of the measured space in 5 measurements according to the following formula to obtain the time temperature fluctuation of the measured space (accurate to 0.1℃).
b,bimax~bimin
wherein: bi-time temperature fluctuation of the ith vertex, i=1~8, C; b——imx the highest temperature of the ith vertex, i=1~8, C; b—imin the lowest temperature of the ith vertex, i=1~8, C. 6.3 Calculation of temperature deviation
The temperature deviation is the synthesis of spatial temperature deviation and time temperature fluctuation. Calculate the temperature difference as follows (accurate to 0.1°C). bi
At,=a+
Where;△t—temperature deviation of the ith vertex, i1~8,°C; a/—temperature deviation of the ith vertex space, i=1~8, Cb—temperature fluctuation of the ith item point, i=1~8,°C. 7. Calculation result processing
7.1 Check the calculation result of Article 6.3 (keep 1 significant digit). If the maximum temperature deviation meets the requirements of Article 3, the measured area is the working space.
7.2 Check the calculation result. If the temperature deviation of the measured space does not meet the requirements of the wire and cable test method standard, the position of the measured space in the test box can be changed or the size of the measured space can be changed and retested. In order to prevent the thermocouple at the center of the original measured space from exceeding 25mm from the temperature sensing end of the thermometer due to the change of the measured space, the position of the lead couple can be moved. At this time, the thermocouple at the measuring point can no longer be located at the center of the measured space after the change. 7.3 This verification method does not include the verification of the test chamber test temperature indicating instrument (or thermometer). For the test chamber where the test temperature is displayed by the temperature indicating instrument and the temperature sensing element of the instrument cannot be located at the center of the working space, the deviation between the value indicated by the temperature indicator and the actual temperature at the center of the working space at the verification temperature should be given in the verification result. 7.4 A verification certificate shall be issued to the test chamber that has passed the verification. The verification certificate format is shown in Appendix A of JB/T4278.1. 7.5 The verification cycle of the low-temperature test chamber is generally set at two years. Additional notes,
This standard was proposed and coordinated by the Shanghai Cable Research Institute of the Ministry of Machinery Industry. This standard was drafted by the Shanghai Electric Research Institute of the Ministry of Machinery Industry and others. The main drafter of this standard is Yuan Baifen.
People's Republic of China
Mechanical Industry Standard
Rubber and plastic wire and cable test instrument and equipment verification method low temperature test chamber
JB/T 4278.81993
Published by the Mechanical Science Research Institute
Printed by the Mechanical Science Research Institute
(No. 2 Shouti South Road, Beijing
Postal Code 100044)
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