Radar Level Commissioning for Communication Networks

Communication commissioning connects a physically correct radar measurement to the control system without losing units, quality or timing. The work differs for 4–20 mA, HART, Modbus RTU and fieldbus, but the acceptance principle is the same: verify a known physical distance, the transmitter's calculated value, every transmitted representation, the PLC tag, operator display, historian and alarm response. A successful ping or changing number is insufficient. The system must identify invalid and stale data, recover predictably after outages and preserve configuration ownership.

Freeze the interface design

Record the exact radar output, power arrangement, cable, barrier, network topology, gateway and control-system channel. Approve tag names, units, ranges, addresses and update rates before field testing.

For digital links, control register or object revisions by model and firmware. For analog loops, calculate available voltage and resistance at the actual supply and cable length.

Verify physical signalling

Measure loop current at known points or confirm RS485 polarity, termination, biasing, shielding and grounding. Inspect cable separation and hazardous-area installation against the approved drawing.

Check for intermittent errors under normal network load, not only with one device connected on a bench. Record error counters and signal observations where diagnostic tools are available.

Prove value conversion

Compare raw radar distance and level with transmitted data, PLC input, engineering scaling and HMI display. Test near zero, midrange and upper range plus unit and decimal boundaries.

For digital values, verify register base, function code, data type, word and byte order. For volume, confirm the controlled tank-table revision and datum.

Map quality and device status

Identify lost echo, low confidence, device fault, maintenance mode, over-range and under-range. Carry useful status into the PLC rather than discarding it at the gateway.

Define which states invalidate control, generate an alarm or permit continued indication. A held last value must show its age and quality clearly.

Test outage and recovery

Interrupt sensor power, field network, gateway and upstream communications separately. Verify alarm delays, local control continuity, data buffering, timestamp handling and operator messages.

After recovery, check for duplicate, reordered or misleading backfilled records. Confirm that the radar and network return to the approved configuration without an uncontrolled write.

Control handover and change

Store the final tag list, register map, addresses, scaling, configurations, firmware and test evidence. Remove temporary forces and engineering overrides and confirm normal scan performance.

Restrict write privileges and record future changes. Recommission affected functions after firmware, gateway, PLC code, network topology or measurement-range changes.

Define measurable network acceptance

Set quantitative acceptance limits for update interval, end-to-end latency, timeout rate, timestamp error and recovery time where those values matter to control or reporting. Record actual results with the normal device count and scan load. A test on an isolated instrument may hide congestion or gateway behaviour that appears only in service. Link exceptions to an owner and retest date, and prevent a communication channel with unresolved stale-value handling from being released for automatic control.

Engineering checklist

Approve the complete interface and tag design.
Test the physical signal under real load.
Verify conversions at several points.
Map device status and data age.
Interrupt each layer and verify recovery.
Store controlled configurations and remove overrides.

Frequently asked questions

Is live Modbus data enough for acceptance?

No. Data type, units, status, fault response and recovery also require testing.

Can HART diagnostics be ignored on a 4–20 mA loop?

They may be optional, but useful status should be integrated when the project depends on remote diagnosis.

What should happen to a stale value?

It should be visibly invalid or stale and trigger the approved process response.

Need a project-specific review? Send process data, drawings, photographs and acceptance criteria through our contact page.