Answer / sam

You can install the PT anywhere on the pipe. It is best to
install on top in crude and slurry application but to
measure water you can install any where, even under the pipe.
If you install on the side or under the pipe fill the
impulse line with water then do a zero on the PT before you
do the final span calibration. Also remember that the
calibration you do on the PT must be exactly the same as to
what your DCS or SCADA faceplate have been scaled to. In
other words if you calibrate the PT for 0 to 20Bar you must
make sure the faceplate in the CCR are also scaled to 0 to
20bar.
Good luck

Answer / carl_ellis

If the transmitter is not directly mounted on the
underground pipe, which is not unusual unless there is
vault access, then an impulse tube/pipe has to come up out
of the ground. The pressure measurement will be in error,
low, by the difference in elevation between the pipe's
elevation and the pressure transmitter's elevation.

Suppose the pipe is 2.1m below the grade level and the
pressure transmitter is 1.6m above grade. The elevation
difference is 3.7m.

The measurement is 3.7m or 0.362 bar low.

It is not unusual to have water supplied at pressure
between at 4-8 bar. At 4 bar pressure, an error of 0.36m
water column is a 9% error, a vary large value for an
insturment capable of 0.25% or better accuracy.

The commissioning of the unit should include the
appropriate zero correction to compensate for such a large
error.

Carl Ellis, Measure First

I work on a electronic positioner transmitter 4211 at the field.I connect my multimeter in series to get the current output then I calibrate it to 4ma in 0% of position of the valve and 20ma in 100% position of the valve.My problem is in the field I get the correct output current based on my multimeter but in the dcs they only receive 40% in a output 20ma of this positioner.Then I try to simulate in this analog card and they receive the equivalent percent on the value that I simulated.Is ther any possibility to reset the zero and span of this positioner 4211 fisher.And what other possibility I can do to fixed this.This is my email add ( landicho_randy@yahoo.com )

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