FAQ on IIoT Pressure Monitoring

Answers to the key questions on connecting pressure and differential pressure sensors to edge devices, MQTT/HTTPS, and your IT/OT systems — including security, topology, intervals, and practical tips.

Are all RS-485/Modbus sensors automatically IoT devices?

No. RS-485 is the field layer. IoT capability only emerges with an edge/gateway (Modbus→MQTT/HTTPS), stable IDs, secure transport (TLS/VPN), and alarm/telemetry logic.

Which protocols typically work together in these architectures?

Field: Modbus RTU, IO-Link, HART. Toward IT/cloud: MQTT or HTTPS/REST — robust polling below, efficient telemetry above.

Can we integrate existing 4–20 mA transmitters?

Yes. Using an edge gateway with analog inputs/HART modem, signals are digitized, scaled, and securely published into your system.

What polling intervals are practical?

Depends on process dynamics, network load, and energy budget. Guidelines:

Do I strictly need a cloud platform?

No. On-prem is possible (local MQTT broker, SCADA/Grafana). Cloud pays off with multiple sites, fleet management, and centralized analytics.

What does a clean MQTT topic scheme look like?

A proven pattern with clear hierarchy and stable IDs:

plant/{site}/line/{unit}/sensor/{id}/pressure
plant/{site}/line/{unit}/sensor/{id}/status
plant/{site}/line/{unit}/sensor/{id}/alarm

How do I secure communication and access?

TLS (MQTTS/HTTPS), per-gateway certificates, VPN/zero-trust, role-based permissions, API keys/certificates, audit logs, signed firmware, and regular patch/certificate management.

Polling or publish-on-change?

Both: Modbus requires polling; the edge additionally publishes “on change” (delta/timeout) to reduce network load and improve responsiveness.

Can alarms be triggered locally at the edge?

Yes. Check thresholds (Hi/Lo, hysteresis), rate-of-change, and deadbands locally; generate timestamped events even if the cloud link is down.

How should I handle units, scaling, and resolution?

Publish unit/scale as retained properties, keep payloads consistent (e.g., Pa or bar), and format server-side. Define fixed units for reports.

What power supply is typical?

How do I design an RS-485 line correctly?

Daisy-chain topology, 120-Ω termination at both ends, biasing, short stubs, clean address assignment, and documentation of baud rate/parity/addresses.

Which baud rates are robust in practice?

Often 9,600–38,400 baud. The longer the cable/more nodes, the more conservative you should be. Shielding, grounding, and correct termination are essential.

How do I integrate IO-Link devices into my IoT?

IO-Link master → edge. Import the IODD, define the process-data cycle, map events, and convert to a unified data model (e.g., pressure.value, device.health).

What belongs in the long-term historian?

Raw values (optionally down-sampled), min/max/avg, alarms/acknowledgements, device status, firmware/config changes, and calibration/maintenance events (for audit/quality).

What does a typical pilot look like?

Workshop → set up edge + 3–5 sensors → mapping & topics → dashboards/alarms → security baseline → acceptance & ROI review → roll-out plan.

Does this work in hazardous areas (ATEX/IECEx)?

Yes, with suitable Ex sensors/barriers and enclosures; place gateways in safe zones, use intrinsically safe interfaces, and provide complete documentation for explosion protection.

How do I detect compressed-air leaks efficiently?

Measure Δp at key points, analyze trends (night base load, rapid drops), apply edge rules (rate-of-change, percentage thresholds), and correlate with compressor starts.

What does integration roughly cost?

Depends on device count and integration depth. Rough guidance:

Which compliance/security points matter?

TLS/VPN, role-based approvals, hardened gateways, patch/certificate management, logging, GDPR-compliant storage, and a clear responsibility/SLA plan.