An analogue input has two contracts: the electrical circuit and the engineering meaning. Commission both. A correct current with the wrong range is wrong data; a correct range attached to an overloaded loop is not a reliable installation.
Define the measurement
Record the instrument tag, physical location, measured property, lower and upper range values, engineering unit, normal and credible fault ranges, transmitter model/configuration and calibration evidence. State whether the signal is live zero, bipolar, reversed or nonlinear.
For every published point, retain raw current or voltage beside the scaled value where practical. This makes wiring, range and saturation faults diagnosable.
Commission a 4–20 mA loop
Determine whether the transmitter is loop-powered or separately powered and whether each input sources or sinks current. Identify every series burden: receiver input, complete outbound-and-return cable resistance, barriers, isolators, indicators, surge devices and any fixed voltage drops.
At the selected design current, the supply must cover the transmitter's minimum terminal voltage plus every entered drop and a deliberate margin. The loop-headroom calculator exposes an infeasible budget instead of calling it zero ohms.
Check maximum component voltage ratings separately. A minimum-headroom calculation does not approve intrinsic-safety parameters, hazardous-area installation, grounding or EMC.
Commission a voltage signal
For 0–10 V and other voltage outputs, verify source range, common reference, polarity, receiver input impedance, output drive capability and isolation. Cable resistance may be less important than for a current loop, while common-mode differences, ground loops, leakage and noise can be more significant.
Do not assume zero volts means zero process value. It may also mean loss of power, broken wire or a configured fault state. Use the voltage-signal scaler with an explicit range and out-of-range treatment.
Prove scaling at known points
Apply or observe at least two traceable points; three or more help detect a reversed or nonlinear map. Verify raw input, scaled result, unit, rounding, timestamp and alarm behavior. At the endpoints, confirm whether the implementation clamps, extrapolates or marks the value out of range.
Use the 4–20 mA scaler for a transparent linear worked example. Scaling arithmetic is not calibration: it does not establish the sensor's accuracy in the process.
Preserve fault states and quality
Define what happens for under-range, over-range, open circuit, short circuit, saturated input, stale data and input-module restart. Do not silently turn a fault current into an ordinary minimum reading. Downstream alarms and calculations should know whether a value is good, uncertain, stale or invalid.
Sampling and filtering must fit the physical process. Record input sample rate, filter or averaging period, publication interval and alarm evaluation method. A one-minute mean cannot prove a one-second pressure excursion.
Acceptance record
Retain the loop or signal drawing, exact instrument/input models, power and burden budget, ranges and units, known-point results, fault tests, sample/filter settings, Edge point mapping and review triggers. Re-test after instrument replacement, re-ranging, wiring or input-module changes.
Continue with industrial process instrumentation, or open System Builder with the instrument list, ranges and loop-power details.
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