A high-performance thermometeor detector detects temperature. Is a good circuit plan enough? In fact, thermal electrometeorology is susceptible to cold temperature interference and requires reasonable design on pcb boards and structures to remove interference. And we're going to explore with the editor how the thermoelectric dolls can be better measured。
What is the reason why some small partners, at the beginning of the design of the circuits, have chosen high-performance thermometric chips and adc, theoretically more than enough to meet performance requirements, but the actual tests have been unsatisfactory? In fact, this rate is due to the unreasonable design of cold temperature. The physical properties of thermoelectric dolls determine that, unlike other sensors, they can only detect temperature differentials, require cold-end temperatures for reference, and the reliability of cold-end temperature tests directly affect the accuracy and stability of thermoelectric measurement. So this cold-end design is particularly important, and we use the demo assessment panel of zam6218a as an example of how high-performance thermometeorograms should be designed。
How to ensure cold temperature accuracy
The temperature at the cold end (reference end) of the thermoelectric doll, which is connected to the measurement circuit, as a reference temperature, has a direct impact on the accuracy of its detection and on the accuracy of the entire temperature measurement programme. The normal cold-end temperature is generally measured using platinum resistance, ntc, digital thermostat chips, etc. The more cold-end temperature is detected close to the real cold-end temperature, the higher the temperature accuracy of the thermoelectric doll as a whole. How, then, can cold-end detection temperatures be brought close to real cold-end temperatures under the same cold-end testing programme? The methodology is actually easy to achieve by adjusting the pcb layout。
We use the example of the pcb sheet of zam6218a in figure 1, where the cold-end temperature detection chip is tmp 116, with the cold end of the thermo-puppet line connected to the detection circuit. The detection temperature of the tm116 of the digital thermochip is less than 0. 1 °c after the layout shown below。
Figure 1 tmp116 cold-end temperature detection pcb sheet board
Pcb board highlights:
How to keep cold temperature stable
Temperature stability in the environment is also very important during thermal electromechanical temperature gathering. Since cold-end sensors do not detect real cold-end temperatures directly through electrical connections, when the real cold-end is in a space environment where the temperature distribution is uneven, there is a large deviation between the temperature detected by cold-end sensors and the actual temperature of the cold-end, which results in large temperature deviations for thermoelectric dolls, which, in the case of relatively harsh environments, can even produce temperature deviations of more than 2°c, such as cabinets with dispersed heat fans, where the wind sector produces an unequally distributed wind speed that significantly affects the detection of cold-end temperatures. So how do we keep the ambient temperature relatively stable
We also take the example of the zam6218a dom evaluation panel, which is illustrated in figure 2 by the design of a metal structure at the cold end of the evaluation panel to reduce environmental disturbance, and by bringing cold-end temperatures from multiple channels to the same temperature line。
Figure 2
Structure design elements:
Zam6218a evaluation panel test
And then we're going to test the temperature accuracy and stability of the thermoelectric dolls through the actual test wave shape. We continue to take the example of zam6218a's dom assessment panel, which supports the temperature measurement of the 8-channel k/t thermal voltage, placing the 8-channel thermal dome detector at the heat end of the 8-channel in a mixture of ice water at 0°c, the ch1-ch4 channel to the k-type thermal voltage, and the ch5-ch8 to the t-type。
Figure 3 zam6218a ice water mixtures temperature curve
Figure 3 shows a curve map of the temperature of the ice water mixture in the 8-channel thermoprompt module, which is 5min in length, showing that the temperature of each channel has a beat value of less than 0. 05°c and that the actual temperature error in detecting the ice water mixture is 0. 12°c. Theoretically, the maximum error of the thermoelectric doll line itself is 27* 0. 4% = 0. 108°c, the maximum temperature error of the cold-end thermostat chip is 0. 1°c, the maximum temperature error of the electro-temperature is 0. 1°c and the maximum temperature error of the overall temperature measurement is 0. 308°c. The maximum error of 0. 12 °c in the actual temperature measurements is a significant reduction in the uneven distribution of temperatures in the environment or the interference of air currents with the temperature properties of the circuits as a result of pcb sheeting and structural additions。
More zam6218a thermometeorometer parameters can be viewed by clicking on the 8-channel thermometeorometer - guangzhou distance electronics inc。
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