Temperature sensors are widely used. Due to the vast differences in operating environments, site conditions, and supporting instruments, engineers, technicians, and maintenance personnel have encountered various problems during use. Based on years of experience, this article briefly analyzes several major causes of temperature transmitter failures.
C2 Fast Response Thermocouple from Chengdu Keda Shengying Technology Co., Ltd.
1. Faults caused by temperature sensor
This is a common and easily diagnosed fault. If an abnormal output from the temperature transmitter occurs during use, first check if the temperature sensor is faulty. Assuming the temperature transmitter circuit is normal, the following situations may occur.
(1) Temperature sensor open circuit. Temperature transmitters have a temperature sensor fuse alarm function. In this case, regardless of whether the front end of the transmitter is connected to a resistance temperature detector (RTD) or a thermocouple, the transmitter output value will be less than the standard signal, i.e., less than 4mA.
(2) Temperature sensor short circuit. At this time, the value output by the temperature transmitter is generally irregular and is an abnormal value, which can be understood as "garbled code" in the software.
(3) Temperature sensor "virtual open circuit and virtual short circuit". This situation usually occurs when the temperature transmitter is working normally at times and not at others. In most cases, the cause is a problem with the temperature sensor packaging quality, and replacing the probe will solve the problem.
2. Faults caused by the power supply
Normal temperature sensors operate within a power supply range of 9 to 30VDC, or 8.5 to 30VDC. Customers commonly use 12VDC or 24VDC DC switching power supplies. Under normal circumstances, the power supply will not damage the temperature transmitter. However, if the power supply malfunctions, it is highly likely to damage the temperature transmitter.
