4-20 mA Signal Helper - Linear Scaling With Review Prompts
Convert between engineering units and 4-20 mA current while keeping NE43, configuration, loop-power, calibration, and safe-work gaps visible
Source-aware 4-20 mA signal screen for instrument technicians and controls engineers. Enter the configured LRV/URV, units, action, and either a measured mA value or a process value to calculate the linear counterpart. The app shows percent-of-span, five-point and 5% scaling tables, and local NE43-style review prompts, but it is not a calibration procedure, loop checkout, transmitter adjustment approval, SIS proof test, or process-safety decision.
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4-20 mA Signal Explained →How It Works
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Enter Configured Range
Input the lower range value (LRV), upper range value (URV), and engineering unit from the live transmitter, DCS/PLC, or loop documentation. The app does not verify that the entered range matches the field device.
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Select Action
Choose direct action when 4 mA maps to LRV and 20 mA maps to URV. Choose reverse action only when the actual configuration maps 4 mA to URV and 20 mA to LRV.
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Enter One Known Value
Enter either a measured mA value to screen the process value, or a process value to screen the mA value. Values outside the configured span are shown as extrapolated local prompts.
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Review Status Prompts
Use the loop-status band as a review prompt. NE43-style thresholds, transmitter fail direction, input-card alarms, filtering, and diagnostics must be confirmed from source data.
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Carry Source Gaps Forward
Before calibration, adjustment, repair, proof test, or process action, reconcile device configuration, loop power, barriers, calibrated references, procedure, permits, bypass state, and qualified review.
Built For
- Instrument technicians screening linear 4-20 mA math before opening the device manual or procedure
- Controls engineers checking draft PLC or DCS scaling values against a local arithmetic prompt
- Maintenance techs documenting which configuration, loop-power, alarm, and measurement gaps still need source review
- Operators converting a known mA value to a process-value prompt without treating it as a field diagnosis
- Commissioning teams building a preliminary five-point scaling table before formal loop checks
- Reliability engineers preserving NE43 and input-card alarm settings as explicit source gaps
- Apprentice instrument techs learning linear live-zero math with calibration boundaries visible
Features & Capabilities
Bidirectional Linear Conversion
Convert from process value to mA or from mA to process value for a user-entered linear range. Reverse action is handled as a source-visible setting.
Scaling Tables
Build five-point and 5% linear scaling tables for the entered LRV, URV, unit, and action.
NE43-Style Review Prompts
Surface local bands around 3.6/3.8 mA and 20.5/21.0 mA while warning that actual alarm interpretation belongs to transmitter and input-card source data.
Source Warnings
Keep configuration, square-root extraction, HART mapping, loop power, barriers, measurement uncertainty, LOTO, permits, and qualified-review gaps visible.
Exportable Report
Export the entered range, local result, scaling table, warnings, assumptions, source pointers, and residual gaps for review records.
Assumptions
- User-entered LRV and URV match the active transmitter, input-card, or controller scaling configuration.
- The screen uses linear 4.0-20.0 mA arithmetic only.
- Reverse action is user-selected and not verified against live configuration.
- NE43-style bands are review prompts, not final alarm approval.
- Loop-power, HART, barriers, grounding, intrinsic safety, and calibrated-reference details are outside the local arithmetic.
Limitations
- Does not validate transmitter configuration, range, trim, damping, fail direction, or alarm settings.
- Does not support square-root extraction, flow cutoff, segmented-linear, or polynomial characterization.
- Does not calculate HART digital overlay data or verify communication margin.
- Does not diagnose wiring faults, ground loops, shielding, barriers, burden, or electromagnetic interference.
- Does not approve calibration, loop checkout, SIS proof testing, hazardous-location work, LOTO, bypassing, or process operation.
References
- IEC 60381-1 - Analogue Signals for Process Control Systems, Part 1: Direct Current Signals.
- ANSI/ISA-50.00.01 - Compatibility of Analog Signals for Electronic Industrial Process Instruments.
- NAMUR NE 43 - Standardization of the Signal Level for the Failure Information of Digital Transmitters.
- ISA-51.1 - Process Instrumentation Terminology.