Multi-channel thermocouple temperature measurement circuit with high channel isolation voltage

Abstract

The invention discloses a multi-channel thermocouple temperature measurement circuit with high channel isolation voltage. The multi-channel thermocouple temperature measurement circuit comprises a thermocouple sensor, an ESD protection module, an RC filtering module, a signal switching module, an AD conversion module, a cold junction compensation unit, a key display unit and a main control unit. The signal switching core adopts a high-voltage-withstanding optocoupler relay, a signal of each thermocouple temperature sensor enters an analog-to-digital converter through the optocoupler relay, thesystem only measures one temperature sensor at any moment, a signal of one thermocouple enters a measurement loop, other signals are in a waiting state, and since the optocoupler relay has high voltage withstanding, therefore, a loop between the channels is blocked, the interference influence between the channels is eliminated, and the circuit cannot be burnt out even if 380VAC is connected between the channels.

Description

technical field [0001] The invention relates to the field of multi-channel temperature measurement and control, in particular to a multi-channel thermocouple temperature measurement circuit with high channel isolation voltage. Background technique [0002] The multi-channel temperature measurement and control module replaces the traditional single-circuit temperature control meter and has been widely used in various automation equipment or monitoring systems that require multi-point temperature measurement and control. Compared with the traditional single-circuit temperature control meter, the multi-channel temperature measurement and control module has low cost, easy installation, and The advantage of small size, but it also increases the interference and isolation problems that must exist between channels. If these problems cannot be effectively solved, in practical applications, unpredictable interference faults or overvoltage burnouts will occur, which will bring disastro...

AI Technical Summary

Problems solved by technology

[0002] The multi-channel temperature measurement and control module replaces the traditional single-circuit temperature control meter and has been widely used in various automation equipment or monitoring systems that require multi-point temperature measurement and control. Compared with the traditional single-circuit temperature control meter, the multi-channel temperature measurement and control module has low cost, easy installation, and The advantage of small size, but it also increases the interference and isolation problems that must exist between channels. If these problems cannot be effectively solved, in practical applications, unpredictable interference faults or overvoltage burnouts will occur, which will bring disastrous results to users. estimated loss

[0003] Due to the complexity of various industrial environments, thermocouples are installed in different parts, and it is inevitable that various interferences such as static electricity, induced electricity, and even strong electricity will be connected in series between each channel. Therefore, these two multi-channel thermocouples are used The product of the measurement method is not stable and reliable enough, and it is easy to measure the temperature inaccurately or burn out

[0004] In addition, in some practical applications, in order to improve the temperature measurement response speed, it is necessary to directly weld the temperature measurement point of the thermocouple to the measured object with strong current (AC 220V or 380V). On the other hand, a high voltage of 220V or 380V will be generated between the thermocouples, and the products using the above two conventional schemes will be burned directly

[0005] In practical applications, due to unreasonable installation and wiring, or no insulating medium inside the thermocouple or poor insulation performance, a strong voltage is introduced between the thermocouples, resulting in damage to the measuring element, which is also a relatively common phenomenon.

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