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We are using Rosemount transmitter to measure basement pressure and the range is:-50Pa to 50Pa. The reading we get, which we do not trust, is -30Pa. Our LP is open to atmosphere via tubing to outside and HP is on the basement side. Please assist.

Hi,

- is it possible to detail us the reference and model of your transmitter?

- we suppose that you performed a calibration at workshop before installation, according to the range +/-50Pa (+/- 0.5mBar)?

- have you the opposite value (+30Pa) if you connect the BP on the basement side with HP to atmosphere?

- are you reading this value on the display of the transmitter on a "PLC", on a work station etc.?

thanks
Bruno

Why not verify the reading with a simple water filled manometer connected in the same manner?

I make 30 Pa = 3 mmWC
Perhaps an inclined manometer or home built Hook gauge

I trust that you are trying to determine ground water pressure in the
basement. The reading of 30Pa converts to about 3mm water column. This looks reasonable, but the -30Pa reading looks as though you have the polarity backwards somewhere, or you are connecting the pressure taps backwards.

Basements leak water because the ground water pressure is higher than the atmospheric pressure in the basement. Why would you ever expect it to be lower. Recalibration of the transmitter to 0 to 100pa would make more sense.

Dick Caro