Calculation sequence
Step-by-step method
- Calculate reference and sensor spans.
- Compare absolute span error with the user-entered screening tolerance.
- Calculate low- and high-point offsets.
MechanicalIntermediateControls
Sensor Offset and Span Calculator
Calculate low-point offset, high-point offset, and span error from two reference and two sensor readings.
Why it matters: A two-point check separates constant offset from span or gain error.
Calculated result
Engineering evaluation
Sensor span error (Esp)-4 %
- Low-point offset (Olo)
- 2 selected units
- High-point offset (Ohi)
- -2 selected units
Engineering interpretation
The two-point check gives -4% span error versus the entered 2% screening tolerance, low offset 2, and high offset -2 in the selected units.
Important limitations
- Two points do not establish linearity, hysteresis, repeatability, response time, environmental effects, or total uncertainty.
Engineering knowledge center
Understand the calculation—not just the answer
Governing relationships
Esp = [(Shi−Slo)−(Rhi−Rlo)]/(Rhi−Rlo)×100
Olo = Slo−Rlo
Ohi = Shi−Rhi
compare |Esp| with Tol
Current substitution
Esp = [( 98−2)−(100−0)]/(100−0)×100 = -4%; Olo = 2; Ohi = -2; Tol = 2%.
Equation legend
Inputs and calculated quantities
- Rlo
- Reference low point — selected units
- Rhi
- Reference high point — selected units
- Slo
- Sensor low reading — selected units
- Shi
- Sensor high reading — selected units
- Tol
- Entered allowable span error — %
- Esp
- Sensor span error — %
- Olo
- Low-point offset — selected units
- Ohi
- High-point offset — selected units
Applications
How this calculation is used
Building design
Define sensor range and accuracy requirements.
Construction
Check wiring, scaling, and installation.
Commissioning
Evaluate sensor offset and span against traceable reference readings.
Quality controls
Assumptions and limitations
Assumptions
- Entered data describe one stable operating condition and use consistent measurement boundaries.
- Time, energy, and performance values are representative of the stated interval.
Limitations
- This is a preliminary evaluation and commissioning-support tool, not an automatic acceptance determination.
- Project sequences, manufacturer data, tariffs, codes, and professional review remain controlling.
Field use
Verification procedure
- Confirm the operating mode, test boundary, and instrument calibration.
- Collect simultaneous readings or a documented trend interval.
- Compare the result with the approved sequence, submittal, and project criteria.
Common engineering mistakes
- Combining measurements from different operating modes or time intervals.
- Ignoring sensor uncertainty, trend sampling, or the defined equipment boundary.
Technical basis
References and source standards
- NIST Measurement and Calibration ResourcesFederal measurement, calibration, timing, and unit-system context.
- International Society of Automation ResourcesControl, instrumentation, alarm, and automation practice context; project sequences and current standards remain controlling.
Engineering calculation disclaimer
These engineering tools are provided for educational, preliminary evaluation, field verification, and commissioning support. Results depend on the accuracy of user-entered information and the assumptions stated for each calculation. Every colored status and comparison is a screening indicator only; project criteria, contract requirements, applicable codes, manufacturer instructions, measurement uncertainty, and authorized engineering judgment govern. The tools do not replace project-specific engineering analysis or the judgment of a licensed professional engineer.
Read the full use and limitation statement