Electrical Power & Protection


Industrial signal conditioning

February 2024 Electrical Power & Protection

Automation for Industry 4.0, process control, data acquisition, and alarm processing all rely on the conversion of physical signals to a standardised, usable format, that engineered systems can reliably use to manage industrial processes. At its simplest, signal conditioning is the process by which physical properties such as temperature, humidity, pressure, vibration, frequency, presence or absence, relay logic and flow are converted by transducers into usable electrical signals suitable for measurement and control systems. Any electronic device that detects and quantifies a physical property like this is referred to in industry as a transducer.

We can think of signal conditioning as an interface between the plant and the field. Control and monitoring systems are sensitive and need to be protected from harsh environments. Voltage spikes, high temperatures, and electrical noise are all potentially damaging, and signal conditioning provides protection to mitigate these harsh field conditions, typically using electrical isolation (galvanic or optical), noise immunity, and surge protection mechanisms.

Field devices or transducers on a process are normally wired back individually from the process to marshalling panels, where the signal conditioning system again converts the signal to the industry standard range of 4-20 mA. From there, multiple signals are run together in multicore cables to control systems.

4-20 mA is used for a number of reasons. 4 mA = 0% , minimum value, and 20 mA = 100% or maximum value. This can be interpreted by the measurement and control system and expressed in SI units. The signal conditioner also allows the field signal to be amplified and zoom in on a portion of the transducer’s range.

This standard exists because a voltage output would result in a volt drop on the cable, introducing an error in measurement, whereas the current output over a long distance can be actively compensated in the system circuitry with voltage manipulation. Additionally, using 4 mA as a ‘live zero’ makes it very easy to detect a system fault, for example a cable break, as the current will fall to true zero.

Challenges of signal conditioning

Electromagnetic interference (EMI) is one of the biggest challenges involved with signal conditioning in industrial environments. Any factors that jeopardise the accurate transmission of signals to the control system must be dealt with. To resolve this, the signal conditioning system is electrically isolated from the plant at an industry standard of 1500 V AC, meaning this is the maximum difference between input and output that the signal conditioner can handle without breaking down.

Signal amplification and attenuation are also issues that require attention. If signals have to travel long distances, tens or even hundreds of metres, they can attenuate because of wire resistance, meaning an inaccurate signal reaches the control system. Similarly, amplification of low-level voltage signals is complex, as any interference or nonlinearities can be amplified along with the desired signal.

All of these challenges are mitigated by the 4-20 mA current range. Current signals naturally withstand EMI better than voltage signals, particularly over long distances. Other control devices can share the current loop as part of the control system.

Signal conditioning is an essential mechanism for industrial plants to collect information and monitor their processes, and only through precise design can plant engineers ensure reliable incoming data flow. Technical issues like signal attenuation, EMI and process safety are all important to consider, but industry standard ranges for signal current and electrical isolation keep things running smoothly.

For more information contact Ian Loudon, Omniflex Remote Monitoring Specialists, +27 31 207 7466, ianl@omniflex.com, www.omniflex.com


Credit(s)



Share this article:
Share via emailShare via LinkedInPrint this page

Further reading:

Power supply with scalability optimised
Schneider Electric South Africa Electrical Power & Protection
Schneider Electric has introduced the Easy UPS 3-Phase Modular to the South African marketplace. This robust uninterruptible power supply (UPS) is designed to protect critical loads while offering third-party verified Live Swap functionality.

Read more...
Prioritising arc flash safety
Comtest Electrical Power & Protection
Comtest has developed a range of thermal imaging and wireless testing tools from Fluke, designed to ensure safety is the top priority for engineers working in potentially dangerous arc flash zones.

Read more...
Monitoring the voltage drop in cables
Turck Banner Southern Africa Electrical Power & Protection
With its new M12Plus connectors, Turck Banner is directly shifting the condition monitoring of cables subject to severe stress to the connection technology. The connectors, which come with voltage and current monitoring and a Bluetooth chip, enable measured voltage and current values to be sent wirelessly to a controller.

Read more...
Mesh networks: a multidirectional electrical superhighway
Schneider Electric South Africa Electrical Power & Protection
Today, many power industry stakeholders are faced with mounting requirements for improved grid reliability, resilience and distribution efficiency. It’s a challenge which requires power service providers to rethink their infrastructure. Enter mesh networks, which can overcome the limitations of traditional star networks.

Read more...
Versatile flexible copper busbar
Electrical Power & Protection
Referro Systems specialises in the supply and support of industrial electrical, automation and global software and hardware brands, and is now able to offer the Cubic range of Cu-Flex flexible copper busbars.

Read more...
Trafo Power Solutions upgrades DRC mine transformers
Electrical Power & Protection
With its experience in Africa and its agility in executing projects rapidly, Trafo Power Solutions is supplying three mini-substations and two transformers to a copper-zinc mine in the Democratic Republic of Congo.

Read more...
Acquiring locally-manufactured transformers
ACTOM Electrical Machines Electrical Power & Protection
Speed and efficiency are of the essence in the fast-evolving power generation and distribution space; but a significant challenge is the prolonged lead times associated with acquiring transformers – key components in any electrical infrastructure.

Read more...
Seaward testers power PV specialists
Comtest Electrical Power & Protection
One of Asia’s leading clean energy specialists, Solarvest, uses the latest electrical safety test equipment to ensure the solar photovoltaic (PV) installations it services and maintains operate at peak performance levels.

Read more...
Multi-purpose contact block
Electrical Power & Protection
The TME catalogue has been expanded to include products from Schlegel. This German, family-owned company has been specialising in the production of high-quality electromechanical components for almost 80 years.

Read more...
ACTOM supplies transformer units to Kamoa Copper Mine
ACTOM Electrical Machines Electrical Power & Protection
ACTOM Distribution Transformers, recently secured an order for the supply of its neutral electromagnetic couplers, with earthing resistors, and an auxiliary transformer) to Kamoa Copper Mine in the DRC.

Read more...