EX shows that this instrument is an explosion -proof instrument: segment A is filled in explosion -proof types, such as D, IA, IB, etc., section B is the category of explosion -proof instruments, such as level I, IIA, IIB, IIC; C is the surface temperature of the explosion -proof instrument. Groups, such as T1-T6. For example: EXDIA I i CT6 indicates that it has explosion-barrier and essential security functions. You can use explosion-proof instruments in the IIC level T6 group.
Failure analysis of differential pressure transmitters
During the measurement process, there are often some faults. Timely judgment analysis and treatment of faults are essential for production. We summarize some judgment analysis methods and analysis processes based on daily maintenance experience.
1: Investigation method. Looking back at the fire, smoke, odor, power supply change, lightning strikes, humidity, accidental operation, accidental maintenance
2: Intuitive method. Observe the external injury of the circuit, the pressure tube leak, the circuit overheating, and the power switch status.
3. Detective method
Disclosure test: Separate the suspicion of the failure part of it. Check whether the fault disappears and disappear, and determine the fault. Otherwise, you can find the next step, such as: the smart differential voltage transmitter cannot be normal to remotely communicate. You can disconnect the power supply from the instrument body, and use the on -site power method to communicate with the sensor to see if the cable is superimposed with an appointment. 2KHz electromagnetic signal and interfere with communication.
Short -circuit detection: In the case of safety, the relevant part of the circuit is directly connected. For example, the output value of the differential pressure transmitter is small, and the pressure tube can be broken. During the bilateral side of the differential pressure sensor, observe the output of the transmitter to judge the block of the pressure pipeline and leak the connectivity.
Replacement detection: The suspected failure part is replaced to determine the faulty area. For example: suspect that the transmitter circuit board fails, it can be temporarily replaced to determine the reason.
Division test: divide the measurement circuit into several parts, such as: power supply, power supply, signal output, signal transformation, signal detection, check from partial inspection, from simplified to complex, from the table and inside, the range of the failure is found.
Temperature Transmitter
The temperature transmitter should be used in conjunction with various thermocouples or thermal resistances, which can convert the test temperature linearly to 0 ～ 10mA or 4 to 20mA DC current signals in order to display, record and adjust the cooperation of the unit.
According to different types of ground temperature measurement sensors, temperature transmitters are divided into three types: DC millival transmitter, resistor temperature transmitter, and thermocouple temperature transmitter.
Its advantage is that low -floating and high -gain ground -based integrated circuits are used to improve the reliability, stability and various technical properties of instrumental ground. At the same time, due to the use of a linear circuit, the transmitter output signal can maintain a linear relationship with the measured temperature model. And the line adopts safety spark explosion -proof measures, which can be used in the temperature measurement in dangerous places.
