Yokogawa EJA transmitter principle and failure analysis

Anyone familiar with the process control industry knows that pressure transmitters are widely used. In a 5000t/d cement production line, the kiln head, the kiln tail, the top and bottom of the preheaters at all levels, each air duct and each room of the cooler, etc., must be equipped with process variable transmitters in these places. The purpose is to Monitoring the normal operation of the process is achieved through the use of these transmitters.

Almost all of the new dry-process cement plants use intelligent pressure transmitters. These intelligent pressure transmitters are mainly: EJA transmitter, CerabarS transmitter, ST700/ST800, SITRANSP and 3051C transmitter. An intelligent pressure transmitter with FF or PROFIBUS-PA protocol is selected. In fact, according to the survey, the application of pressure transmitters in actual production is very huge. A total of about 80 pressure transmitters are required for a new dry process cement production line.

Now everything is changing with each passing day in the 21st century, and transmitters tend to develop towards digital intelligent transmitters. These third-generation transmitters use advanced detection technology to eliminate moisture, dust and other on-site harsh environments. Transmitter measurement effects. The adoption of advanced detection technology makes the accuracy better than 0.05%, the range ratio is expanded to 200:1, the range is finer, and the stability is more than 5 years; The transmitter guarantees a safe shutdown.

With the continuous development of the Shinkansen cement production line, the position of the pressure transmitter in the production application is increasing day by day.

Principle of digital pressure transmitter

1. Measuring element and EJA pressure transmitter transmitter: For example, to perform liquid level measurement, EJA transmitter transmitter can realize liquid level measurement, and convert the liquid level into a specific and unified output signal , such as air pressure signal or voltage, current signal, etc. Generally, the EJA transmitter transmitter mainly outputs the current signal of the two-wire system;

2. Automatic controller part: This part must accept the signal sent by the EJA transmitter transmitter, in order to achieve the comparison with the liquid level height that the process must maintain, and further obtain the deviation. The purpose of obtaining the deviation is to calculate the result according to a certain operation rule, and then send the result with a specific signal pressure or current;

3. Actuator part: This part mainly refers to control valve and ordinary valve, which realizes some special functions. The controller relies on the signal sent by the EJA transmitter, and finally calculates and processes the specific signal, and then the actuator can automatically change the valve opening according to the signal value.

It can be seen from the above introduction that each part of the automation control industry is an interlocking process. As an important part of the automation control industry, the EJA transmitter transmitter has played an immeasurable role in the progress of the automation control industry. effect.

Output exception

There will be some situations in the actual use of the EJA transmitter, which makes people feel at a loss. In fact, as long as the root cause is found, these problems can be solved very well.

Some customers may encounter: the pressure goes up, but the output of the EJA transmitter does not go up, and then the output of the EJA transmitter does not change after pressurizing, and the output of the EJA transmitter changes suddenly when the pressure is continued, and the EJA transmitter is depressurized. Can't go back to zero.

Usually you will be very distressed at this time, but the most important thing is to find out what the problem is and solve it. If this happens, check whether the pressure interface is leaking or blocked. If not, you need to check the wiring method and power supply. When everything is normal, check whether the zero position of the sensor of the EJA transmitter has output. , or simply pressurize to see if the output changes. If there is a change in this way, it proves that the sensor of the EJA Yokogawa transmitter is not damaged. If there is no change, it means that the sensor has been damaged.

In the end, it is necessary to consider whether the instrument has been damaged, or whether there is a problem with other links in the entire system.

Improve anti-interference

Once the pressure sensor has poor anti-interference and is easy to be interfered by the outside world, its value is reduced, and its application range is greatly limited. Pressure sensor is one of the most widely used sensors in sensors, and it is widely used in industry, agriculture and service industries.

The pressure sensor obtains information by directly contacting or approaching the measured object. Both the pressure sensor and the measured object are in a disturbed environment at the same time, and are inevitably disturbed by the outside world.

Especially piezoelectric pressure sensors and capacitive pressure sensors are susceptible to interference. The anti-interference measures of pressure sensors generally start from the structure. Smart pressure sensors can also be solved in software.

To improve the structure of the pressure sensor, the introduction of interference can be avoided to a certain extent. There are the following ways: the signal processing circuit and the sensitive elements of the sensor are integrated into a whole, that is, integration. In this way, the signal to be transmitted is enhanced, and the anti-interference capability is improved. At the same time, because it is integrated, the introduction of interference is reduced; the integrated sensor has the characteristics of compact structure and strong function, which is conducive to improving the anti-interference ability; intelligent sensor can take anti-interference measures in software from various aspects, Such as digital filtering, timing self-calibration, characteristic compensation and other measures.

Once the pressure sensor has poor anti-interference and is easy to be interfered by the outside world, its value is reduced, and its application range is greatly limited. Pressure sensor is one of the most widely used sensors in sensors, and it is widely used in industry, agriculture and service industries. There are applications in a variety of environments, so interference immunity must be fairly reliable. At present, the pressure sensor can be used in many environments, but in some environments, the anti-interference of the pressure sensor is not good enough. We must combine high-tech from multiple angles to further improve the anti-interference of the pressure sensor.