Differential pressure transmitter used as an intelligent transmitter
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For flue gas desulfurization, a differential pressure transmitter was chosen at that time; a pressure transmitter was used. The flue gas operates under negative pressure of -3 to -5 KPa – is it connected to the H terminal of the transmitter? Still the 3L end?
1. It’s best to specify the principle, model, and brand of the differential pressure transmitter. 2. Not all differential pressure gauges allow the sensor to be subjected to pressure in the reverse direction. 3. Even in those devices that permit reverse pressure application, since the gauge isn’t calibrated for this condition before leaving the factory, and since the sensor isn’t a measuring element that produces perfectly symmetric outputs, applying pressure in the reverse direction will inevitably lead to accuracy issues. 4. When considering accuracy and operational lifespan, it’s advisable not to apply pressure in the reverse direction; this approach is always beneficial. In other words, connect the high-pressure terminal H of the differential pressure gauge to the ambient atmosphere, and connect the low-pressure terminal L to the process fluid. If the differential pressure gauge you’re using allows for setting a sensitivity factor, set this factor to -1; this way, the reading displayed on the gauge will carry a negative sign, indicating a negative pressure value. If such a function isn’t available, or if there’s no capability for numerical calculations, then you need to multiply the displayed value by -1 in order to get the correct value
Either end can be connected; just make sure to set the range properly.
For such a range, it’s better to use a high-quality differential pressure transmitter; otherwise the measurements will be inaccurate. Connect the pressure conduit to the H terminal of the differential pressure transmitter, and set the range to -3 to -5 KPa
Right now, the reading from terminal L shows 0.32 Kpa; it should be negative pressure of -0.32 Kpa, right?
It can be used in the same way as well; just connect the smoke to H and L to the atmosphere
If the on-site setup is changed, the control system also needs to be changed; otherwise, it won’t match. Previously, with positive pressure, -5 corresponded to 4 milliamps; now, with negative pressure, 3 corresponds to 4 milliamps. If the field conditions change and the DCS configuration does not adjust accordingly, the display on the operation interface will no longer match the values from the field transmitters.
Measure negative pressure; connect positive pressure, which is H
This post was last edited by feng*aosa on 2018-2-1 at 19:34. All of them can be connected. Connected to the H side; the transmitter needs to be relocated. The higher the pressure, the greater the output signal, and no additional configuration is required for the DCS ； On the L side, the transmitter does not need to be moved; the higher the pressure, the lower the output signal. The DCS requires additional configuration, and it is inconvenient to use other indicators for monitoring.
The positive-pressure chamber is connected to the atmosphere, while the negative-pressure chamber is connected to the measuring tube or equipment. The range is set to 0–10 kPa, and a minus sign is added in front of the displayed value.