The pressure at a remote instrument can differ from the pressure at the named process point. Retain the vertical liquid column in the measurement model.
Locate the two pressure elevations
WIKA’s capillary guidance identifies hydrostatic effects when a filled connection links different elevations. The relevant head depends on vertical height and fluid density. Total tube length and vertical height are different dimensions; a long horizontal run does not create the same hydrostatic head as a vertical column.
Calculate an invented column
For a hypothetical liquid density of 900 kg/m³ and a 1.0 m downward elevation from the process tap to the sensing point, ρgh is 900 × 9.81 × 1.0 = 8,829 Pa, or about 8.83 kPa. In the stated static arrangement, the lower point has the additional pressure.
Reverse the elevation and the head direction reverses. This calculation ignores other installation influences and is not a correction for an actual instrument. Draw the process tap, sensing point, liquid-filled path and elevation sign before assigning any correction.
Request the applicable installed relationship
Ask which fill or impulse fluid is present, what density information applies, and how the approved instrument configuration accounts for the head. Preserve the reference elevation with the result. Do not silently reinterpret a remote reading as process-tap pressure because both display the same pressure unit.
Primary reference: Manufacturer technical reference.
Instrument evidence worksheet
This blank worksheet is for your own project. It contains no H M machine trial result.
| Review question | Evidence to retain |
|---|---|
| Where is the pressure required? | Named process point and elevation |
| Where is it sensed? | Instrument elevation and filled path |
| What head model applies? | Density, height and sign convention |
Customer Questions
Is total tube length the hydrostatic height?
No. Use the vertical elevation difference.
Does the example supply a real correction?
No. Actual fluid and geometry must be established.
Can the pressure unit alone identify the measurement point?
No. Retain the location definition.
Primary References
These references support the technical principles discussed in this guide. The worked examples and review questions are educational.
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