Temperature is a physical volume indicating the degree of cold and heat. Microscopically, it is the intensity of the thermal movement of the object molecules. In the cold chain industry, if fresh food and medicine Lose temperature will lead to food deterioration and inedibility, drugs could not achieve curative effect, and even lead to fatal accidents.
When selecting temperature measuring equipment related to temperature sensors in the cold chain industry, suppliers are often asked several questions by customers:
1. Is the temperature measurement accurate?
2. Is the external temperature sensor accurate or the built-in sensor accurate?
The first question, we should start with the principle explanation of temperature sensors. Electronic temperature recorders used in the cold chain industry of the Internet of things mostly use the following two types of contact temperature sensors:
1. Analog sensor: NTC sensor and PT sensor. These sensors mostly use the resistance change caused by the temperature change of the sensor internally, and then convert and obtain it through the voltage value AD data and the comparison table between temperature value and voltage value. The temperature accuracy is affected by the following factors:
1.1, consistency and reliability of sensor material;
1.2, consistency and stability of voltage reference in circuit design;
1.3, consistency and stability of voltage signal processing circuit (amplifier);
The above differential conductance will lead to the accuracy and cost of temperature recorder. The cost of PT is higher than NTC, and the accuracy is also higher.
2. Chip data sensor, These sensor uses integrated circuit to package analog circuit, which has high consistency and is conducive to development, but higher cost and narrow testable temperature range.。
The above two types of sensors are widely used in the cold chain industry. In addition to using PT in dry ice and liquid nitrogen environment, NTC and chip sensors can be targeted to use.
The Actual temperature is not completely constant due to the large space and door open of storage house. The temperature built in shell, battery and PCB will made thermal radiation to improve the thermal time constant of the whole temperature recorder. The final appearance is as follows:
1. It takes 30 minutes for the temperature to drop to - 20 ℃ after being placed in - 20 ℃ environment from room temperature 20 ℃, and some recorders even delay for 60 minutes.
2. The response to temperature changes lags behind, and it is possible to ignore the peak caused by temperature changes.
In addition, for some temperature recorders with wireless communication, the circuit will also heat the product due to unreasonable design, which further leads to inaccurate measurement of temperature recorders. In contrast, the temperature recorder in the form of external probe does not have the above problems.
Based on the above, in the cold chain application, the built-in temperature recorder can be used in the environment with relatively constant temperature and low requirements for temperature time ductility; In the environment with large temperature change and sensitive to temperature, the temperature recorder in the form of external probe needs to be used first. If the external temperature recorder cannot be used due to structural problems, it must also consider pre cooling the equipment.
FANSO BATTERY produces LiMnO2 soft ULTRA THIN pack battery, which can continue to work under low temperature conditions and support various wireless transmission current and voltage platforms. It is suitable for the whole supply chain process, including storage, transportation and freezer display. The battery supports customer customized thickness, which can further make a more suitable physical design reference for temperature records.
Previous：
Geomagnetic vehicle detector/sNext：none
