Zero-point issue with EJA438W? Urgent!
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Hello everyone! When measuring the pressure in a sealed container, the distance between the installation position of the EJA438W diaphragm-sealed pressure transmitter and the height of the flange diaphragm is approximately 5 meters. The transmitter’s range is -0.1 to 1.5 MPa. How should the zero point be adjusted? Is it necessary to adjust the pressure value corresponding to the level of the fluorinated oil sealed inside the capillary tube?
It should be double flange. Suggestions: 1. If the measurement range for liquid level is -0.1 to 1.5 MPA, which is too wide, the range should be changed. 2 Liquid density. Fill fluid density.
It is necessary to transfer down the pressure value corresponding to the height of the fluorine oil sealed inside the capillary.
The poster should describe the working environment of the gauge, such as the medium, temperature, pressure, and whether the transmitter itself is located above or below the diaphragm box. If it’s above, there will be negative drift; otherwise, there will be positive drift. There’s no need to mention the calculation formulas. But why is 438W used for measuring pressure? Is the medium prone to clogging? High temperature?
The pressure generated by the medium inside the capillary should be removed.
First, eliminate the pressure difference in the capillary within 5 meters and adjust the zero point. Set the range to 0-1.6 Mpa and then change the lower limit to -0.1 Mpa; the transmitter’s range will thus be -0.1-1.5 Mpa
In terms of measurement range, this is a flanged absolute pressure transmitter. I have an idea that you can give a try: Assume the atmospheric pressure is 0.1 Mpa. When the pressure-taking valve is closed and the vent valve is opened, the instrument’s output should be {0.1 Mpa/Mpa} * 16 mA + 4 mA = 10.6 mA. If the output is not 10.6 mA, adjust the zero point to make it correct; this process is essentially migration. At this point, the instrument can be activated normally
Method 2: Close one valve and open the vent valve. Using a handheld programmer, the pressure value x exerted on the transmitter is read; the lower programming limit is (x–0.1) Mpa, and the upper limit is (x+1.5) Mpa. This post was last edited by Behind the moon on 2009-3-21 at 21:07
Thank you all for your responses. It’s either an absolute pressure transmitter or a single-flange pressure transmitter, with chlorine as the medium. The transmitter unit is located below the diaphragm box. How do I zero it using the Yokogawa HART handheld controller? Should I first change the range to 0-1.6 MPa after installing the transmitter and confirming that the pressure inside the tank is 0, then set that pressure as the zero point, and finally adjust the range back to -0.1-1.5 MPa? This is because the handheld controller cannot directly set the current actual pressure (0 MPa) as 5 mA
Reply to the original poster: Use HART to select the transmitter’s sensor reset option to zero it out, change the range to -0.1MPA to 1.5MPA, and then turn on the gauge to put it into use.
Such a question is simple. Of course it needs to be migrated, and it should be a positive migration. Specific procedure: First, close the stop valve in front of the flanged diaphragm, then loosen the flange screws; at this point, the pressure acting on the diaphragm is atmospheric pressure. Assume that the pressure generated by fluorine oil in a 5-meter-long capillary is X MPa. (Here, we assume that the internal pressure of the transmitter is zero; by internal pressure being zero, it means that when the diaphragm and the transmitter are at the same level, the transmitter outputs 4 mA while the gauge displays 0%). ) At this point, use the manual controller to change the range to X~~(X+1.6) MPa. If the internal pressure is not zero, simply add that value to X; add it for positive values and subtract it for negative values.
Sorry, let me correct that. The range has not changed to X~~(X+1.6); instead, it is (X-0.1)~~(X+1.5) MPA
Let me explain in more detail: this amount of migration is easy to calculate; it’s a positive migration. By multiplying the density of fluorine oil by G and then by 5 meters, the result is 0. Adding this value to the range gives the full scale value. Of course, the range is already specified in the control device specifications. If the transmitter itself is located above the diaphragm box, then the same negative migration calculation method is applied.
I am looking for a detailed Chinese user manual and calibration instructions for the Yokogawa YHC 4100 HART handheld communicator. Thank you!
The normal range is 0---xxx MPa. The pressure resulting from a 5-meter drop must be added to this value; let’s denote this value as Y. After adding it, the range becomes Y---xxx+Y MPa. The value of Y can be negative