Telemetry

What is telemetry?

Telemetry is the automated measurement of data at a remote or hard-to-reach location and its transmission over a communication link to a central system, where the data is monitored, stored and analysed. The word comes from the Greek tele (far) and metron (measure). Within OT environments, telemetry provides real-time insight into industrial processes: process values, statuses, faults and energy consumption of pumping stations, substations, wind turbines, machines and vehicles. In the Dutch water and energy sectors, the central location where this data converges is often called the hoofdpost (master station).

Telemetry is the data foundation for, among others:

• SCADA - the classic supervisory layer that visualises and operates telemetry from RTUs and PLCs
• Industrial Internet of Things - connected sensors and machines that publish their own data
• Industry 4.0 and the digital twin - virtual models fed with current measurements
• Industrial AI and predictive maintenance - models that recognise patterns and deviations in measurement series

🧠 What data does telemetry provide?

A telemetry system measures operational data and sends it to a central system for monitoring, analysis or control. Typical data types:

A measured value without context is of little use. Good telemetry therefore sends a timestamp and a quality flag (good, uncertain, invalid) with every value, so that a historian and downstream analytics know whether the value can be trusted. Forecasts and KPIs are not telemetry in themselves, but they are derived from it.

🔧 How does a telemetry system work?

A telemetry chain consists of several layers, from the field to the dashboard. Data flows from field level up to higher OT and IT layers, as described in the Purdue Model and the underlying architecture.

A telemetry process usually runs through these steps: data collection, filtering, normalisation (units, scaling), transmission, storage, analysis and visualisation. Three mechanisms separate a reliable system from an unreliable one:

• Deadband - an analogue value is only sent again once it has changed by more than a configured threshold, saving bandwidth without losing relevant information
• Store-and-forward - when the link drops, the outstation buffers measurements and events locally and forwards them later with their original timestamps, so there are no gaps in the history
• Time synchronisation - outstations set their clocks via NTP, GPS or, where high accuracy is needed, Precision Time Protocol; without synchronised clocks, the sequence of events after a disturbance cannot be reconstructed

🔄 What is the difference between polling and report by exception?

There are two ways to collect telemetry. With polling, the master station asks each outstation in turn for its current values. With report by exception, the outstation sends data itself as soon as something changes.

In practice, telemetry systems combine both. DNP3 performs an integrity poll at start-up to obtain a complete picture and afterwards mainly collects buffered events, divided into three priority classes; a periodic integrity poll (for example hourly or daily) checks that nothing has been missed. Sparkplug solves the failure-detection problem of report by exception with birth and death messages, so that consumers know whether a value is current.

🌐 Which protocols and links are used for telemetry?

MQTT is a telemetry protocol at heart: Andy Stanford-Clark (IBM) and Arlen Nipper (Arcom) developed it in 1999 to monitor oil pipelines over expensive and unreliable satellite links. That is why it is frugal with bandwidth and tolerant of dropped connections. Fieldbuses such as ProfiNET, by contrast, are designed for real-time communication within a single installation; they deliver data to the PLC or gateway, which then sends the telemetry on to the master station.

Choose the transport medium based on distance, bandwidth and energy budget. Fibre and microwave links offer the highest reliability, 4G/5G is flexible, and LoRaWAN (868 MHz in Europe) and NB-IoT suit battery-powered sensors that send a few messages per hour. Watch out for the retirement of old mobile networks: in the Netherlands, KPN and VodafoneZiggo have already stopped 3G, Odido switched off its 2G network in 2023, and KPN plans to end 2G in December 2027. Telemetry units that only speak GPRS must therefore be replaced in good time.

🏭 Where is telemetry used?

Within industrial automation, telemetry systems collect data from many sources:

Typical sectors include:

• Water management - the 21 Dutch water boards and the drinking water companies monitor thousands of pumping stations, weirs, reservoirs and treatment plants from a central location; see Water Sector OT Security
• Energy - inside substations, protection relays and IEDs increasingly communicate via IEC 61850, while substations, wind farms and solar parks usually send their measurements to the grid operator’s control room via IEC 60870-5-104
• Industry - condition monitoring, OEE measurement and energy monitoring in support of LEAN and asset management
• Logistics and mobility - vehicle tracking systems and AGV fleets

Telemetry can be processed locally or centrally. Edge computing filters and aggregates data close to the source, which reduces latency and network load and keeps local analysis running when the link is lost. The cloud is mainly used for long-term storage, AI training and central dashboards across multiple sites. Hybrid architectures combine both and are the most common in practice.

🔐 How do you secure telemetry?

Telemetry is both a security risk and a source for detection. Whoever manipulates telemetry makes operators decide on the basis of false information. In December 2016, the Industroyer malware of Sandworm used, among others, IEC 101 and IEC 104 to switch circuit breakers in Kyiv; many classic telemetry protocols have no built-in authentication.

Where data only needs to flow from OT to IT, a data diode guarantees that telemetry can leave without creating a path back in. Encryption of data streams and logging of all connections belong on every telemetry link over a public network.

Conversely, telemetry feeds security. Network and system telemetry goes to a SIEM, a SOC, an IDS and SOAR platforms, enriched with threat intelligence and used for anomaly detection. After an incident, the same telemetry is the main material for forensic analysis. Since 15 August 2026, many operators of telemetry in water and energy fall under the Dutch Cybersecurity Act, with a duty of care and an obligation to report significant incidents; see also cybersecurity.

🛠️ How do you set up a telemetry system?

A practical approach in six steps:

1. Define the information need - which decisions must operators, maintenance and management take, and which measuring points do they need for that
2. Record the requirements per measuring point - measuring range, unit, deadband, required freshness (seconds for alarms, minutes for trends) and retention period
3. Choose protocol and link - IEC 104 or DNP3 for classic telecontrol, MQTT with Sparkplug for IIoT, and a transport medium that will still be supported in ten years
4. Design for failure - store-and-forward in every outstation, heartbeats, redundant links for critical sites and high availability of the master station
5. Secure from the start - segmentation according to IEC 62443, encrypted connections, managed remote access and an up-to-date inventory of all outstations
6. Monitor data quality - check for frozen values, impossible jumps and clock drift before data ends up in analytics or AI models

Key challenges remain large data volumes, legacy outstations without security, inconsistent sensor data and scalability as the number of devices grows.

❓ Frequently asked questions

What is the difference between telemetry and SCADA?

Telemetry is remote measurement and the transmission of that data to a central point. SCADA is the system that receives the telemetry, visualises it, raises alarms and lets operators intervene remotely. Telemetry is therefore the data stream, and SCADA the supervisory and control layer above it.

Which protocol is best suited for telemetry?

For classic telecontrol in the European energy and water sectors, IEC 60870-5-104 is common, while North America mostly uses DNP3. For new IIoT applications and cloud connections, MQTT, often with Sparkplug, is widely used because of its low overhead and publish/subscribe model. The choice depends on your existing installations, available bandwidth and security requirements.

What happens to telemetry data when the connection drops?

A well-designed outstation buffers measurements and events locally and sends them with their original timestamps as soon as the link is restored. This is called store-and-forward. Without this function, gaps appear in the history and alarms raised during the outage are lost.

How often should telemetry be sent?

That depends on the purpose: alarms and status changes should be reported immediately, while trend values are often fine at intervals of seconds to minutes. With a deadband, an outstation only forwards an analogue value once it has changed noticeably. This keeps network load low without losing relevant information.

Is telemetry over the mobile network secure?

Telemetry over 4G or 5G can be secure if the connection runs through a private APN or VPN, the data is encrypted and outstations are not directly reachable from the internet. Unsecured modems with a public IP address are a well-known attack path. In the Netherlands, also take the retirement of 2G and 3G networks into account.

Does telemetry fall under the Dutch Cybersecurity Act?

The Dutch Cybersecurity Act (Cyberbeveiligingswet) applies to organisations in designated sectors, such as drinking water, waste water and energy, not to a technology as such. The telemetry systems of such an organisation do fall under its duty of care, because they are essential to the service. The act entered into force on 15 August 2026.

📌 In summary

Telemetry is the automated measurement of data at a distance and its reliable transmission to a central system, making it the data foundation for SCADA, IIoT and predictive maintenance. A good telemetry system combines the right protocol and transport medium with deadbands, store-and-forward, time synchronisation and security according to IEC 62443.