Calculator Inputs
Example Data Table
This example assumes a standard heavy manometer fluid with identical connected fluids on both sides.
| Case | Left Fluid | Right Fluid | Manometer Fluid | a | b | g | ΔP |
|---|---|---|---|---|---|---|---|
| Water vs water, mercury column | 1000 kg/m³ | 1000 kg/m³ | 13600 kg/m³ | 0.35 m | 0.20 m | 9.80665 m/s² | 18.535 kPa |
| Oil vs water, heavy oil manometer | 850 kg/m³ | 1000 kg/m³ | 1200 kg/m³ | 0.40 m | 0.28 m | 9.80665 m/s² | 0.824 kPa |
Formula Used
Main equation:
ΔP = Pleft − Pright = g[(ρm − ρL)a − (ρm − ρR)b]
Here, ρm is manometer fluid density, ρL and ρR are connected fluid densities, a is the left tap-to-interface depth, b is the right tap-to-interface depth, and g is gravitational acceleration.
Corrected result with calibration offset:
ΔPcorrected = ΔPraw + Offset
Interpretation:
A positive result means the left side pressure is higher. A negative result means the right side pressure is higher. When both sides are equal, the corrected differential pressure is effectively zero.
How to Use This Calculator
- Select whether your fluid values are entered as density or specific gravity.
- Enter the left, right, and manometer fluid values.
- Enter the vertical tap-to-interface depths for both legs.
- Choose the length unit, then confirm gravity.
- Enter any calibration offset if your instrument needs correction.
- Pick the preferred output unit and submit the form.
- Review the result block above the form, inspect the graph, then export CSV or PDF if needed.
Frequently Asked Questions
1. What does this calculator solve?
It estimates the differential pressure between the left and right sides of a U-tube manometer using fluid densities, tap-to-interface depths, gravity, and any optional calibration offset.
2. Can I enter specific gravity instead of density?
Yes. Choose the specific gravity option, then enter dimensionless SG values. The calculator converts each one to density by multiplying by 1000 kg/m³ before solving the pressure equation.
3. What do a and b represent?
They are the vertical distances from each pressure tap down to the interface between the connected fluid and the manometer fluid. Use the same unit on both sides.
4. Why might the result be negative?
A negative corrected differential pressure means the right side pressure exceeds the left side pressure. The sign helps you understand direction, while the magnitude shows how large the pressure difference is.
5. Why is there a warning about fluid density?
Traditional U-tube differential manometers often use a manometer fluid denser than the connected fluids. If your entry breaks that pattern, the calculator still works mathematically, but your setup may require extra physical review.
6. What is the calibration offset for?
Use the offset to account for known bias in your instrument, installation, or reference zero. The calculator adds this correction after computing the raw differential pressure from the fluid columns.
7. What does the graph show?
The Plotly graph shows a sensitivity line. It varies the left tap-to-interface depth while holding the other current inputs constant, so you can see how the differential pressure changes.
8. Which output unit should I choose?
Choose the unit that matches your report or instrument convention. The calculator also shows the corrected pressure in several alternate units, making it easy to compare engineering and laboratory formats.