Parameter setting of absolute pressure transmitters
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This post was last edited by nmgsbl on 2012-4-17 at 11:28. The company measures the pressure at the top of a pressure relief tower using an absolute pressure transmitter, with a measurement range of 0 to 100 kPa. The normal operating pressure is –70 kPa. So how should the field instruments and the DCS be set up in order to accurately reflect the actual value? It has been returned to the manufacturer for verification.
-70KPA is gauge pressure, which needs to be converted to absolute pressure based on the local atmospheric pressure. The signal provided by the transmitter corresponds to the absolute pressure, and the display also shows the absolute pressure.
Just set the measurement range of the DCS to be the same as that of the field instruments. . . . . . . . . . . . .
This post was last edited by panhui323 on 2012-4-12 at 15:29. Of course, it should be set to 0–100 KPa; when the pressure is -70 KPa, both the DCS and the gauge will display 30 KPa. What is displayed is the gauge pressure.
One standard atmosphere is 101.325 kPa, and the normal operating pressure is –70 kPa; thus, the absolute pressure is 31.325 kPa. The gauge pressure meter has a range of 0-100 kPa, so you just need to set your DCS to 0-100 kPa as well.
Is it 0.03 MPa or 0.03 kPa? However, under normal pressure the gauge shows 0 kPa; when the system is under negative pressure of -70 kPa, it displays -10 kPa. Was the zero point adjusted at normal pressure during installation?
The EJA510A gauge pressure transmitter, along with Hilscher systems – this is a very common scenario here; the transmitter’s range is set to 0~100KPa； DCS configuration range setting: -100~0 KPa
I’m sorry, I typed it wrong. . . It has been changed. It should be 30kpa:$
This post was last edited by nmgsbl on 2012-4-12 at 16:08. Hello, what value will be displayed on the gauge under normal pressure after making this setting? What does the DCS display? Is the transmitter connected to the positive pressure chamber or the negative pressure chamber?
This post was last edited by changzhigang on 2012-4-12 at 16:20. The range is from 0 to 100 kPa, and this refers to gauge pressure; the operating pressure of -70 KPa does not represent gauge pressure – it needs to be compared with the local atmospheric pressure. If the local atmospheric pressure (which depends on the local altitude) is 89 KPa, then 89 – 70 = 19 KPa, so the gauge pressure is 19 KPa. Therefore, when setting the values, the transmitter should be set within the 0–100 KPa range, while the DCS should be set between -89 and 11 KPa (assuming the local atmospheric pressure is 89 KPa). OK! ! !
I set it this way on the assumption that the local atmospheric pressure is 100 KPa! At atmospheric pressure, the transmitter gauge reads 100 KPa, while the DCS shows 0 KPa. The transmitter is of course connected to the positive pressure chamber! The negative pressure chamber of a pressure transmitter is usually blocked! Do you understand?