Signals
What this tool does
Scale a process value to loop current, including linear and square-root transfer. This page says what the tool is for, in plain language. The working formula stays on the signed-in tool.
When to use it
Open 4–20 mA analog scaling when this is the job: Scale a process value to loop current, including linear and square-root transfer. That is usually a loop check, a range change, or a signal that does not match the panel.
Step-by-step
- Open 4–20 mA analog scaling from the tool list.
- Fill Transfer, LRV, URV, Process value from the instrument, the drawing, or the job record. Use the unit shown beside each field.
- Fill the remaining fields the same way. Skip a field only when the screen marks it optional.
- Run Calculate when that control is on the page, then read every result row and any warning.
- Check the result against the site procedure and the manufacturer data before you change a range, a wire, a setpoint, or a weight.
- A free account can open this tool after signing in.
Inputs
- Transfer
- Linear uses the span directly. Square root is for a differential-pressure flow signal.
- LRV
- Lower range value. The process reading at the bottom of the calibrated span.
- URV
- Upper range value. The process reading at the top of the calibrated span.
- Process value
- The live reading you are scaling, in the same engineering units as the range.
- Supply
- The DC supply voltage at the loop or the transmitter.
- Transmitter minimum
- The lowest voltage the transmitter is allowed to see while it is still in spec.
Results
- Result
- The reported value for 4–20 mA analog scaling. Use the unit printed on that row.
- Warnings
- A warning means an entry is incomplete or outside what this tool will stand behind. Recheck the inputs and the site procedure.
Common mistakes
- Swapping the lower range and the upper range, or typing the live reading into a range field.
- Treating a square-root flow signal as if it were a linear span.
- Changing a range while a warning is still on the screen.
- Do not treat a result from 4–20 mA analog scaling as a substitute for the site procedure or the manufacturer data.
Standards references
These are the standards and public references named on this tool. Clause numbers appear only when the catalog already cites them.
- ISA process-control practice for 4–20 mA scaling
- NAMUR NE43 (fault current thresholds)
- HART loop-resistance guidance (public HART documentation)
Offline and access
This engine can run offline after the server has cached it for the signed-in account.
A free account can open this tool in the workspace.