Calculator Inputs
Example Data Table
| Case | Base LRV | Base URV | Manual Shift | Wet Leg | Safety Margin | Expected Design Range |
|---|---|---|---|---|---|---|
| Tank level service | 0.0000 bar | 10.0000 bar | 0.0000 bar | 2.00 m | 5% | -0.3039 to 10.6961 bar |
| Filter differential | 0.0000 kPa | 50.0000 kPa | 1.5000 kPa | 0.00 m | 2% | 0.5000 to 52.5000 kPa |
| Gas header monitoring | 5.0000 psi | 75.0000 psi | -1.0000 psi | 0.00 m | 3% | 1.9000 to 76.1000 psi |
Formula Used
Offset = (Density × 9.80665 × Wet Leg Height) ÷ 1000
Total Offset = Manual Zero Shift ± Hydrostatic Offset
Adjusted LRV = Base LRV + Total Offset
Adjusted URV = Base URV + Total Offset
Span = Adjusted URV − Adjusted LRV
Design LRV = Adjusted LRV − (Span × Margin %)
Design URV = Adjusted URV + (Span × Margin %)
Linear Output = Output Low + ((Live Pressure − Design LRV) ÷ Design Span) × Output Span
Square-root Output uses √((Live Pressure − Design LRV) ÷ Design Span) before scaling.
How to Use This Calculator
- Select the pressure type and engineering unit.
- Enter the base LRV and URV from your intended calibration range.
- Add any manual zero shift required by installation or setup practice.
- Enter wet leg height and fluid density to include hydrostatic head.
- Set the safety margin to widen the design envelope.
- Enter sensor minimum and maximum values to check capability.
- Choose the output scale, then enter a live pressure reading.
- Enable square-root extraction for flow-style differential measurements.
- Use reverse acting when output must decrease as pressure rises.
- Press calculate to display the result summary, chart, CSV, and PDF exports.
Frequently Asked Questions
1. What do LRV and URV mean?
LRV is the calibrated lower pressure. URV is the calibrated upper pressure. Together they define span and the transmitter’s usable output map.
2. Why does wet leg height affect range?
A wet leg creates hydrostatic head. That pressure adds to or subtracts from the sensed pressure, shifting both calibration endpoints.
3. When should square-root extraction be used?
Use square-root extraction mainly for differential-pressure flow measurements, where flow is proportional to the square root of measured pressure difference.
4. What is zero suppression versus zero elevation?
Zero suppression shifts the calibrated range upward. Zero elevation shifts it downward. Both change the endpoints without changing the basic process span.
5. What does the turndown ratio show?
Turndown compares the sensor’s full capability with the chosen calibrated span. Large turndown can reduce practical accuracy if excessive.
6. Can this calculator handle negative ranges?
Yes. Gauge and differential services can include negative values. Absolute service should stay above zero absolute pressure.
7. Why should I add a safety margin?
A safety margin provides operating cushion for surges, drift, and uncertainty. It helps avoid clipping the transmitter near actual process extremes.
8. Why might the design range exceed the sensor limit?
Offset, widened margins, or a narrow sensor selection can push the design endpoints outside the transmitter’s capability. Verify the datasheet range.