GB/T 11465-1989 Thermal distribution diagram of electronic measuring instruments GB/T11465-1989 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Thermal profile for
electronc megsurlng instrumests1 Subject content and scope of application
1.1 Subject content
This standard specifies the test method for the thermal profile of electronic measuring instruments (hereinafter referred to as instruments). 1.2 Scope of application
GB 11465—89
This standard is applicable to obtaining the thermal distribution data of instruments and systems and verifying whether the thermal design meets the expected requirements. It can also be used as a basis for evaluating reliability indicators.
When multiple instruments are used to form a cabinet system, the thermal profile can also be used to find the best assembly form. 2 Reference standards
t. GB 6587.1 General outline for environmental testing of electronic measuring instruments GB2903 Copper-Constantan thermocouple wire and graduation table GB4993 Nickel-Chromium-Constantan thermocouple wire and graduation table GB913 Nickel-Chromium-Copper thermocouple wire and graduation table 3 Terms and symbols
3.1 Terms
3.1.1 Temperature critical components and devices
Components and devices whose surface temperature is close to the maximum allowable operating temperature. 3.1.2 Average value of component and device temperature
According to the formula in 6.1.1, the temperature value is called the average value of the component and device temperature. 3.1.3 Component and device surface hot spot temperature
The temperature of the component and device surface close to the highest point of temperature rise. 3.1.4 Temperature stability
When the temperature of most components and devices (including the components and devices with the largest heat generation) changes by no more than 2 degrees per hour, it is called temperature stability.
3.1.5 Surface area and total surface area
Surface area refers to the design area of ​​a certain surface of the instrument. The total surface area refers to the sum of the design areas of all surfaces of the instrument, and the area related to the vertical surface of the radiator is not included. 3.1.6 Thermal time constant
The time required for the temperature of the components and devices to reach 63% of the value after the power is turned on and the temperature stabilizes. 3.2 Symbols
Approved by the Ministry of Machinery and Electronics Industry of the People’s Republic of China on March 31, 1989 and sold on January 1, 1990
A: Surface area of ​​the instrument, m;
A: Total surface area of ​​the instrument. m*
Ip: Temperature of the hot spot on the surface of the component or device, °C; Lu: Average temperature of the component or device, °C; 1: Air temperature around the instrument, °C;
t: Temperature of the test room (or box) wall, °C;
2m: Average ambient temperature, °C;
ta: Humidity of the instrument casing, °C;
P: Power consumption of the component, device or instrument, W, V. Air velocity, m/s;
: Thermal time constant, ht
t: Time, h.
4 Test content and test requirements
4.1 Test content
4.1.1 Temperature of hot spots on the surface of temperature-critical components and devices. G 11465—89
4.1.2 Temperature of hot spots on the surface of all components and devices whose actual power consumption exceeds 1% of the total power consumption of the instrument. Among them, for components and devices with similar installation positions and the same power consumption, only the temperature of representative hot spots on the surface of components and devices can be sampled. 4.1.3 Temperature of hot spots on the surface of components and devices with the largest heat generation. 4.1.4 External surface temperature of the instrument chassis.
4. 1.5 Temperature of the wall of the test room (or test box). 4.1.6 Air temperature around the instrument.
4.1.7 Air temperature at key points inside the instrument 4.1.8 Air temperature at the outlet of the air duct of the air-cooled instrument. 4.1.9 Air flow rate of the air-cooled instrument.
4.1.10 Surface area of ​​the instrument.
4.1.11 Total power consumption of the instrument.
4. 1. 12 Thermal time constant.
4.2 Test requirements
4.2.1 The environmental conditions of the heat distribution test shall be in accordance with the provisions of GB6587.1 and the air flow velocity shall be less than 0.2m/s. If there is no doubt, it can be carried out in the corresponding indoor environment or test box. Then, the data shall be extrapolated to the maximum operating temperature of the instrument according to formula (3) in Article 6.1.3. 4.2.2 During the test, the instrument shall be in normal working condition (all covers shall be in place) and there shall be no additional heat dissipation channels. The instrument shall be placed horizontally. It is not allowed to prop up the bracket under the instrument. 4.2.3 The instrument shall be tested under the working condition that causes the maximum heat consumption. 4.2.4 During the test, a thermocouple temperature sensor shall be used. The thermocouple shall be welded with a thermocouple wire with a diameter less than 0.25mm. Its thermoelectric potential shall comply with the corresponding graduation table of GB2903, GB4993 and JB913. When the thermocouple used may affect the temperature field of the component, a thermocouple wire with a smaller diameter should be used. Other temperature sensors can also be used without affecting the temperature field. 4.2.5 Test: 1 The maximum allowable tolerance of the test equipment used is: a:
Temperature, ±2C;
Flow rate, ±5%,
Power, ±5%.
4.2.6 When measuring the surface temperature of the charged component and the temperature of the surrounding environment, the sensor should have sufficient electrical insulation performance. 4.2.7
When there is a strong alternating electromagnetic field at the measured point or in the space where the thermocouple wire passes, the thermocouple wire should be shielded. 5 Test method
5.1 Selection of test point location
GB 11465-89
5.1.1 The temperature test point of the component and device should be at a place that is accessible to the surface of the component and device and can produce the highest surface temperature. When it is impossible to determine, it should be selected based on experiments.
5.1.2 The air temperature of the surrounding environment of the instrument should be measured by installing a temperature sensor 76mm away from the geometric center of each major surface of the instrument.
5.1.3 According to the structural characteristics of the instrument, select several key points inside the machine to measure the air temperature. 5.1.4 Place a temperature sensor at the center of each major surface of the instrument chassis to measure the surface temperature of the chassis. 5.1.5 The test point of the air temperature at the outlet of the duct is selected at a distance of .7D from the axis of the fan (for exhaust-type instruments), or at the outlet with the largest air volume close to the inside of the chassis (for blast-type instruments). 5.1.6 Select three points on the plane at a distance of (0.6~0.7)D from the fan along the axis of the fan to measure the flow rate and take the average value. Note: D is the diameter of the fan.
5.2 Installation of Thermocouple
Measurement
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Figure 1 Schematic diagram of isothermal contact
5.2.1 When measuring surface temperature, use an easily removable adhesive with good thermal conductivity to fix the measuring end of the thermocouple on the surface of the measured element or device in the form of isothermal contact, as shown in Figure 1. 5.2.2 When measuring space temperature, the measuring end of the thermocouple should be firmly fixed on the auxiliary support and must not move or contact any heat-generating object.
5.3 Test steps
5.3.1 Determine the test content according to the provisions of Article 4.1. 5.3.2 Select the temperature test point according to the provisions of Article 5.1. 5.3.3 Fix the thermocouple according to the provisions of Article 5.2. 5.3.4 Restore the instrument to the normal closed state and place it for more than 4 hours. 5.3.5 Turn on the power supply and immediately measure and record the temperature-critical components, devices and other meaningful temperatures at intervals of 2 minutes. Until the temperature stabilizes.
Note: The meaningful temperature refers to the temperature of the most representative components and devices and the changing ambient temperature. 5.3.6 Turn on the power supply and test all test points every 30 minutes. When the instrument enters the temperature stabilization, the data will be recorded in the record form, see Appendix A (Supplement).
5.4 System test
According to the structural characteristics of the system, select the following key test points and perform heat distribution test on the system according to the steps in Article 5.3. 6 Test results
6.1 Data processing
GB 11465--.89
6.1.1 The average temperature of the components and devices is calculated according to formula (1). In the formula: m——the average temperature of the components and devices, ℃! P,—actual power consumption of the element, device, W
tm---the temperature of the hot spot on the surface of the element, device, C; 1
element. Number of devices.
6.1.2 The average ambient temperature is calculated according to formula (2), which will be used as a single ambient temperature value for various calculations. ZA.[()+(ra).
Where.t..
Average ambient temperature, C,
Surface area of ​​a certain surface of the instrument, m,
——air temperature around the instrument,,
Temperature of the test room (or box) wall, °C, total surface area of ​​the instrument, m,
Number of surfaces.
6.1.3 Use the data tested under indoor environmental conditions to extrapolate the maximum operating temperature of the instrument according to formula (3). tg=t,+(tet)
Where, — extrapolated temperature value, °C; t
Actual temperature value, °C1
ra——upper limit of the instrument operating temperature, °C. 6.2 Plotting
6.-2.1 Use the extrapolated values ​​of the data recorded in 5.3.5 to plot the temperature change curve of the temperature-critical components, as shown in Figure 2. (1)
（3）
6.2.2 Select several important test points to make a temperature distribution point diagram (see Figure 3) and a plane position diagram (see Figure 4) for the estimated values ​​of the data recorded in Article 5.3.6.
yuan, courseware (2) the maximum temperature allowed
GE11465-89
yuan, the maximum temperature allowed for the item
yuan. 8, Allowable temperature and pressure
Environmental temperature
Temperature change curve of critical components and devices 10
Figure 3 Temperature distribution histogram of important test points inside the instrument 245
6.3 Conclusion
GB11465—89
Front panel direction
Figure 4 Planar distribution of key test points inside the instrument Top view Designers should use the test results to make judgments and take appropriate improvement measures, and then conduct one or more tests until they believe that the thermal design of the instrument meets the requirements.
6.4 File processing
The test results include test records, curve charts and test reports. See Appendix B (Supplement) and archive them together with the environmental test report. No.
Ambient temperature
Air temperature near the top of the instrument1
Air temperature near the bottom of the instrumentt
Air temperature near the front of the instrument1
Air temperature near the rear of the instrument
Air temperature near the right side of the instrumentt,
Air temperature near the left side of the instrumentt
Temperature of the opposite chamber wall of the top of the instrument
Temperature of the opposite chamber wall of the bottom of the instrument1a
Temperature of the opposite chamber wall of the front of the instrument1a
Temperature of the opposite chamber wall of the rear of the instrumentte
Temperature of the opposite chamber wall of the right side of the instrument1.
Temperature of the opposite chamber wall of the left side of the instrument
Instrument temperature
Temperature of the outer shell of the top of the instrument
Temperature of the outer shell of the bottom of the instrument
Temperature of the outer shell of the front of the instrument
Temperature of the outer shell of the rear of the instrument,
Temperature of the outer shell of the right side of the instrumentt.
Temperature of the left shell of the instrumenttbzxZ.net
Surface temperature of temperature-critical components and devices
Temperature of other inspection points inside the instrument
Parameters of air-cooled instruments
Temperature of the air duct outlet.
Air flow rate
Other parameters
GB 11465—89
Heat distribution test data
(supplement)
Measured value
Estimated value
Outer surface area of ​​instrument body 1
Outer surface area of ​​instrument bottom 4
Outer surface area of ​​instrument front A
Outer surface area of ​​instrument rear Λ
Outer surface area of ​​instrument right A
Outer surface area of ​​instrument left A
Total power consumption P of instrument
Organized data
Total surface area of ​​instrument A
Average value of element and device temperature
Average ambient temperature te
Time constant of instrument?
GB 11465—89
Continued Table A
Actual Measured Values
Note: When testing 7 to 12 items, if the indoor temperature is not different, you can only measure the temperature of 2 to 4 points instead. When the instrument case is non-surfaced, you can add corresponding test points according to the specific situation. Appendix B
Test report
(supplement)
Test instrument model
Test instrument name
Environmental group
Cooling method
Total power consumption
Temperature-critical components and devices
Test results and treatment opinions:
Test date
Signature of test operator
Additional notes:
Component and device name
Position number in the circuit diagram
Signature of technical person in charge
This standard was drafted by the Electronic Standardization Institute of the Ministry of Machinery and Electronics Industry. Allowable maximum temperature
Estimated value
Actual maximum surface temperature
(Estimated value)Corresponding pilot projects can be added according to specific circumstances. Appendix B
Test report
(supplement)
Model of test instrument
Name of test instrument
Environmental group
Cooling method
Total power consumption
Temperature-critical components and devices
Test results and treatment opinions:
Test date
Signature of test operator
Additional notes:
Name of components and devices
Position number in the circuit diagram
Signature of technical person in charge
This standard was drafted by the Electronic Standardization Research Institute of the Ministry of Machinery and Electronics Industry. Allowable maximum temperature
Estimated value
Actual maximum surface temperature
(estimated value)Corresponding pilot projects can be added according to specific circumstances. Appendix B
Test report
(supplement)
Model of test instrument
Name of test instrument
Environmental group
Cooling method
Total power consumption
Temperature-critical components and devices
Test results and treatment opinions:
Test date
Signature of test operator
Additional notes:
Name of components and devices
Position number in the circuit diagram
Signature of technical person in charge
This standard was drafted by the Electronic Standardization Research Institute of the Ministry of Machinery and Electronics Industry. Allowable maximum temperature
Estimated value
Actual maximum surface temperature
(estimated value)
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