Should an absolute pressure transmitter be used to measure a pressure of 0.002 MPa?

There is no need for an absolute pressure transmitter; a regular differential pressure transmitter will suffice. The EJA110 has diaphragm ranges of 0.5–10 KPa. An absolute pressure transmitter is used only when negative pressure occurs within the measurement range; it is necessary when the value is between -0.005 and +0.005, and a significant amount of offset must be adjusted to ensure a certain level of accuracy

Can a pressure transmitter be used? Is the range too large, resulting in insufficient precision?

The pressure measurement isn’t accurate; firstly, a range of only 2 KPa is not sufficient for proper measurement. Use differential pressure, with negative pressure being vented to the atmosphere

This statement is also problematic; it isn’t necessary to use a differential pressure approach. If the negative pressure chamber is connected to the atmosphere, it becomes difficult to obtain accurate readings when there is wind. The Rosemount 3051s1 series can measure pressures in the range of -6.22 to 6.22 kPa, and the 3051CG1A model can also do so (with flanges). Whether to use gauge pressure or absolute pressure depends not on the presence of negative pressure, but rather on whether the process conditions normally involve negative pressure – that’s the principle

After checking, it is indeed true that the 3051CG can measure values ranging from -6.22 to +6.22 KPa, which makes it suitable for the situation described by the original poster as well. I have another question for the person above: under normal operating conditions, the pressure should be slightly positive, but there are situations in which the gauge operates under negative pressure (assuming such situations occur fairly often). Can the diaphragm of a pressure transmitter withstand this? Is the diaphragm of a gauge-type transmitter more resistant to negative pressures, thus less likely to experience problems? What are the structural differences between absolute pressure and gauge pressure transmitters?

This situation is quite common; any manufacturer that produces transmitters is capable of handling it. The reason it is referred to as a normal operating condition, one involving long-term use, is that if a transmitter diaphragm operates under conditions of pressure imbalance for an extended period, it will undergo flexible deformation. In other words, gauge pressure transmitters are prone to such flexible deformation when exposed to positive pressure over a long time. There isn’t much difference in structure between gauge pressure and absolute pressure transmitters; the difference lies in their reference points. For more details, please refer to the section on pressure transmitters

Could you provide some samples of Rosemount from upstairs? Thank you very much. I only have EJA samples. Which is better, the EJA differential pressure transmitter or the Rosemount pressure transmitter? What about the cost?

Both of these have good quality, and the prices should be similar. I’m not sure if the EJX transmitters offer pressure transmitters with the range you need. I have Chinese documentation for the ROSEMOUNT 3051 here, but the file upload area has limits on file size. Please leave me your email address and I’ll send it to you. According to our usual design practices, differential pressure transmitters are generally chosen for such applications. But the wind pressure issue mentioned on the 6th floor does exist. This post was last edited by hwindforce on 2009-3-2 15:22]

Thank you so much. My email address is 307725953@qq.com

Whether to use a pressure transmitter or an absolute pressure transmitter depends on the process operations.

The original post was posted by longniu on 2009-3-2 at 11:56. This statement is also problematic; it’s not necessary to use differential pressure. If the negative pressure chamber is connected to the atmosphere, it becomes difficult to obtain accurate readings when there is wind. The Rosemount 3051s1 series can measure values ranging from -6.22 to 6.22 kPa. Whether to use gauge pressure or absolute pressure depends on whether the process conditions normally involve negative pressure; this is the principle. ======================================== Even when the process normally operates under negative pressure, there are still issues with choosing a gauge pressure transmitter. For example, when the process is normal, the negative pressure varies between -2 and -1 kPa. If 3051CA-1 is selected (URL: 207 kPa, LRL: 0 kPa, Min.Span: 2.1 kPa, range 0–110 kPa), when the pressure value varies between -2 and -1 kPa, the corresponding measurement values on the scale can only vary between 98 kPa and 99 kPa. This range represents less than 1% of the range of an absolute pressure transmitter, making it impossible to obtain accurate measurements ； Only differential pressure or gauge pressure can be selected. This post was last edited by wen*da on 2009-3-2 17:51]

Then install the transmitter indoors; differential pressure is a reliable method. Alternatively, bring the negative pressure chamber inside as well. Otherwise, it’s impossible to obtain accurate readings. I’m not sure how those experts upstairs measure the negative pressure in the boiler furnace – they use differential pressure, I guess. My estimate is that maintenance would need to be carried out every 2 to 3 days. In 2007, two 35T boilers were installed; theoretically, using differential pressure should work well, but in practice it didn’t. In situations where certain theories don’t hold true, other methods can still work quite well – it’s better not to be too dogmatic

Could considering migrating the gauge pressure transmitter be an option?

“Should an absolute pressure transmitter be used to measure a pressure of 0.002 MPa? ”Regarding this issue, I don’t think there’s anything to discuss; there’s definitely no need to use an absolute pressure transmitter. This range isn’t particularly small, so either domestic or international products should be suitable for it. During use, measuring in kilopascal range is not that difficult, but measuring in pascal range is actually the more challenging task. Especially the range of 0 to 200 Pascals is really tough! A friend upstairs said that measuring the negative pressure of the boiler is indeed a difficult task. However, its range is generally in the positive and negative pascal range, so it’s relatively better.

0–200Pa differential pressure transmitters are suitable for this purpose

For such a small range, the effect of changes in atmospheric pressure must be taken into account. We use differential pressure transmitters to measure the pressure in atmospheric tanks; those with such a large range work very well! By the way, we use E+H; we’ve been using it for 8 or 9 years now.

Brother upstairs, the E+H meters aren’t very good, especially when it comes to micro-differential pressure; the Swiss people deceive people in our country