FAQ on IIoT Pressure Monitoring

Here we answer the key questions about connecting pressure and differential pressure sensors to edge devices, MQTT/HTTPS, and your IT/OT systems — including security, topology, sampling intervals, and practical tips.

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

No. RS-485 provides field communication only. It becomes IoT-capable 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 level: Modbus RTU, IO-Link, HART. Toward IT/Cloud: MQTT or HTTPS/REST. This separation enables robust polling in the field and efficient telemetry upstream.

Can we integrate existing 4–20 mA transmitters?

Yes, via an edge gateway with analog inputs/HART modem. The gateway digitizes, scales, and securely publishes values into your system.

What polling intervals are practical?

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

Do I 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?

Transport via 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 on the server side. Define fixed units for reports.

What power supply is common?

Typical voltages and notes:

How do I plan an RS-485 line properly?

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

What does a typical pilot project 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-certified sensors/barriers and enclosures; place gateways in safe areas, use intrinsically safe interfaces, and provide full documentation for the explosion protection file.

How do I detect compressed-air leaks efficiently?

Δp measurements at key points, trend analysis (night base load, rapid drops), edge rules (rate-of-change, percentage thresholds), correlation with compressor start events.

What does integration roughly cost?

Depends on device count and integration depth; rough guidance:

Which compliance/security points matter most?

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