[Daily Question] What is the working principle of a pressure transmitter and where should it be installed?
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Figure 1 shows the pressure transmitter newly installed at the bottom of the tank on site, while Figure 2 is a schematic diagram of the equipment in this storage tank. Previously, the DCS display was linked to the magnetic flap level gauge; that is, the DCS display was based on the movement of the magnetic flaps on site (I don’t know why this is the case either – could any experienced colleague help explain it?). However, the range of the magnetic flaps did not cover the entire tank, so approximately 20% of the upper part of the tank was not displayed (it remained at 100% even when the tank was full). The DCS only started to show changes in liquid level once the liquid surface reached the upper part of the magnetic flaps; therefore, that upper 20% area represented a blind spot for monitoring by operators. Later, it was changed to the structure shown below, with pressure induction at the bottom; the gravity of the liquid stored there is used to convert it into a pressure signal that is then transmitted to the control panel, resulting in greater accuracy. Question: 1. What is the internal structure of this pressure transmitter like? Is there a probe inserted into the pipeline? 2. From a precision perspective, is there an issue with the installation location of the transmitter? Should it be led out from the midpoint on the side of the pipe?
Pressure transmitters come in two forms: the direct installation type, in which the transmitter is equipped with a pressure gauge connector; one end of this connector has threads that are screwed directly onto the transmitter, while the other end is welded directly to the process pipeline. With this method, the gauge head can be firmly supported merely by the transmitter connector. 2. The pressure intake pipe installation method requires support for the gauge head; in other words, it necessitates the use of various brackets, as you mentioned. 3. Mounting brackets generally fall into two types: panel mounting and pipe mounting. Pipe installation refers to 2\" pipes, which are generally flat-mounted or come in L-shaped versions. The panels are all L-shaped and can be fixed to the dashboard or to vertical surfaces such as walls. Note: Points 1 and 2 mainly discuss the installation methods of transmitters. Those who have experience with instruments should be able to understand this, but it’s difficult for those with less knowledge of instruments to explain it in words. You can search for PDF sample materials such as those related to \"Rosemount transmitters\" or \"EJA transmitters\"; once you see the pictures, everything will become clear. For transmitters that use pressure induction, a bracket (or clamp) is required for fixation, and the bracket types are either flat support type or L-type.
A device that converts physical measurement signals or ordinary electrical signals into standard electrical signals for output, or that enables output via communication protocols. They are generally classified into: temperature/humidity transmitters, pressure transmitters, differential pressure transmitters, level transmitters, current transmitters, power transmitters, flow rate transmitters, weight transmitters, etc. An intelligent transmitter is composed of a sensor and a microprocessor (microcomputer). It makes full use of the computing and storage capabilities of microprocessors to process sensor data, including the conditioning of measurement signals (such as filtering, amplification, A/D conversion, etc.), data display, automatic calibration, and automatic compensation. The microprocessor is the core of intelligent transmitters. It can not only calculate, store, and process measurement data, but also adjust the sensors through a feedback loop to ensure that the collected data is of the highest quality. Due to its various software and hardware capabilities, the microprocessor can perform tasks that are difficult for traditional transmitters to accomplish. Therefore, smart transmitters reduce the difficulty of manufacturing sensors and significantly improve their performance. In addition, smart transmitters also have the following features: 1. They possess automatic compensation capabilities, allowing for automated correction of sensor nonlinearities, temperature drift, and time drift through software. It can perform self-diagnosis; upon power-up, it conducts a self-check of the sensor to verify that all its components are functioning properly and to make a determination accordingly. Data processing is convenient and accurate; it can automatically handle data according to internal procedures, such as performing statistical analyses or removing abnormal values. 2. It has two-way communication capability. Microprocessors can not only receive and process sensor data but also send information back to the sensors, thereby adjusting and controlling the measurement process. It can store and retain information, capable of storing characteristic data of sensors, configuration information, and compensation parameters, among other things. 3. It features a digital interface output function, allowing the output digital signals to be easily connected to computers or field buses, etc
The voltage transformer shouldn’t have a probe extending into the medium, right?
Judging from the appearance of this transmitter, it is likely a capacitive or monocrystalline silicon transmitter, without probes. The installation location is acceptable; it shouldn’t be too close to the bottom, as this can lead to blockages and affect measurements. For accurate measurement, it is necessary to calculate the height and the density of the medium in order to determine the range.
Installation was no problem; there are no needles – it’s a diaphragm pressure transmitter, so the range needs to be calculated carefully
Thank you for your thoughtful answer. Since I’m not majoring in instrumentation, my knowledge in this area is quite limited. However, thank you for pointing me in the right direction; I’ll go and look up information on “Rosemount transmitters” right away. If I have any questions, I’ll come back to ask you :)
Well, I asked the technician in charge of the device today; there are no probes used here – instead, the pressure is measured by connecting it directly to the pressure tapping via threads.
It’s not very clear what specific type it is; there are no probes. The installation location is about 20 cm above the bottom of the tank, which has a vent for removing debris from the bottom. Additionally, the previously given height values were not very accurate, which caused the DCS level display to show an out-of-range reading; however, normal operation was restored after re-measuring the height.