Instrumentation & Calibration
Compare an instrument indication against an applied reference and express the signed error in engineering units and percentage of calibrated span.
Field use
Use this when checking a single applied point against the instrument indication. The tolerance entered here must come from the approved calibration requirement or applicable procedure.
A negative error means the instrument indicates below the applied reference. A positive error means it indicates above the applied reference.
Pass/fail compares the absolute % span error against the entered tolerance. AccessRA does not assume an instrument accuracy class or site calibration tolerance.
Interpretation
A positive error means the instrument reads higher than the applied reference; a negative error means it reads lower. The sign helps describe direction, while pass/fail uses the absolute magnitude against the entered tolerance.
Worked example
If the reference is 500 psi and the instrument indicates 515 psi, the signed error is +15 psi. With a 1000 psi calibrated span, the error is +1.5% of span. A ±1% span tolerance would therefore fail at that point.
Practical boundary
A single-point check cannot by itself distinguish zero, span, linearity or hysteresis behaviour. Use a multi-point upscale/downscale calibration when the condition of the complete measurement range must be assessed.
Engineering Knowledge