Temperature rise test model construction is very important for electronic product performance evaluation. The temperature rise curve not only assists engineers in verifying the reliability and rationality of product design, but also provides a more comprehensive assessment of the overall performance of the product. So how do you test to get an accurate temperature rise curve?
First, the temperature rise test
In order to verify the lifespan, stability and other characteristics of electronic products, the temperature rise of important components (IC chips, IGBTs, etc.) is usually tested, and the device under test is placed at a specific temperature (such as room temperature or a specific temperature). After operation, the temperature rise of the component above the ambient temperature is recorded, and the reliability of the product and the rationality of the product design are verified by determining whether the temperature rise of each component of the product meets the allowable value specified in the standard.
The purpose of temperature rise is to collect the temperature change of each test point: observe whether the temperature curve change is reasonable, such as whether the temperature rise is within the allowable range; if there is an abnormality, stop the test, save the existing data, and view and analyze the cause. Figure 1 shows the temperature rise record.
Figure 1 Temperature rise curve
So how does temperature rise record and operate?
1. Traditional test methods
After using ordinary data acquisition to collect the working temperature of the tested object, manually use EXCEL to do a lot of data calculation, the working temperature of the measured object - fixed room temperature value; but the traditional method costs a lot of labor costs, the test results are not accurate.
2. New digital mining test method
The delta difference between the input (test object operating temperature) and the reference channel (test ambient temperature, such as room temperature) is measured by the Delta method as the measured value of the channel. In the temperature measurement, the difference between the measurement and the room temperature is facilitated based on the room temperature. As shown in Figure 2.
Figure 2 operation model
Second, the test environment to build
For example, at room temperature 25 ° C, the power supply temperature rise test, that is, on the surface of all critical components, such as IGBT, inductors and other semiconductor devices or magnetic devices, usually use thermocouples (R, S, B, K, E, J, T, N type) wiring.
Figure 3 test method
Thermocouple solder joint: the thermocouple probe is placed close to the measured position and glued;
Thermocouple wiring: The wires inside the machine should be as neat as possible, tied with high temperature tape, walking groove or wire slot;
Thermocouple outlet: Do not lead from the inlet or outlet or other unsafe locations.
When there are two different conductors or semiconductors A and B form a loop, when the two ends are connected to each other, as long as the temperature at the two junctions is different, the temperature at one end is T, which is called the working end or the hot end, and the temperature at the other end is T0. It is called the free end (also called the reference end) or the cold end. An electromotive force is generated in the loop. The direction and magnitude of the electromotive force are related to the material of the conductor and the temperature of the two joints. This phenomenon is called "thermoelectric effect". The circuit composed of two kinds of conductors is called "thermocouple". These two kinds of conductors are called "hot electrodes", and the generated electromotive force is called "thermoelectromotive force". The temperature rise process is determined by this model.
Third, multi-level cascaded distributed acquisition
When the measurement sites are scattered, the measurement site can be installed separately from the data logger to avoid connecting the signal wires over long distances. Multiple cascading, DM100 data acquisition recorder can be expanded to up to 200 acquisition channels, which is highly scalable and suitable for multi-channel data acquisition and recording. Figure 4 shows the cascading mode.
Figure 4 Cascade mode
Fourth, the data summary operation
The analog signal acquisition modules are all sampled by 32-bit ADC. The DC voltage accuracy is up to 0.05%. Simultaneous sampling can be performed between modules. The fastest sampling period is 100ms/10 points. The isolation between the channels is 1000V AC, which effectively shields the interference between the channels. The built-in digital filter can effectively eliminate power frequency and high frequency noise interference, adapt to changes in the field environment, and work stably in the industrial environment to obtain accurate raw operational data. Figure 5 shows the data exported by the web form.
Figure 5 Web data
ZLG Zhiyuan Electronics DM100, DP100 data acquisition recorder is a general-purpose data acquisition device. It provides users with diverse data acquisition modules through modular design framework, and comprehensively collects DC voltage, DC current, digital quantity, temperature and humidity. A variety of sensor signal data, real-time operation and display a variety of measurement results. The user can perform custom operation processing on the collected data and realize high reliability data storage and recording function. The DM100 and DP100 data acquisition recorders provide users with a convenient and reliable data acquisition instrument from data acquisition and measurement operations to storage and recording.
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