Follow the finding
back to the evidence.

Reported symptom

The SCADA flow display shows a value ten times higher than the field instrument.

Scope

One flow measurement, from the field display through the PLC and gateway to one SCADA display. Three stable observations during a fictional 30-minute period. No configuration changes.

01 / Observations

All displayed values are labeled L/min. The gateway’s outgoing numeric value is expected to use the same unit.

Matched: the field display, PLC value and gateway output agree at all three observations.
Mismatch: the SCADA display is consistently ten times the gateway output.

02 / Finding and confidence

The first observed discrepancy lies between the gateway’s outgoing value and the SCADA display. An extra scaling conversion is a plausible explanation, but these observations do not establish the exact configuration responsible.

03 / Limits and items not tested

• Actual flow accuracy or instrument calibration.
• Electrical signal integrity between the instrument and PLC.
• Behavior outside the three observed values or observation period.
• Historian records, alarms, control logic or other tags.
• The configuration responsible for the discrepancy.

Agreement between displayed values does not establish that the underlying physical measurement is accurate.

04 / Prioritized next actions

1. Have the customer’s authorized SCADA owner inspect the receiving tag’s mapping, units and scaling settings.
2. Document any proposed correction and obtain customer approval before authorized staff make changes.
3. Repeat the comparison across the expected operating range after any correction.
4. Check related historian values and alarms separately if they use the same measurement.