Signal Transducers

The accuracy class defines the maximum permissible error with respect to the true value and directly affects the accuracy of the measurement system. For general monitoring applications, an accuracy of ±0.5% may be sufficient, while for automatic control or energy metering systems, classes of ±0.2% or better are recommended. Furthermore, transducers with temperature compensation and a low drift coefficient ensure long-term stability even in environments with temperature variations. Correctly selecting the accuracy class reduces error propagation along the measurement chain and improves the quality of the acquired data.

To ensure full compatibility, it is necessary to verify that the transducer’s output signals are supported by the acquisition or control system’s inputs (e.g., 4-20 mA for industrial PLCs). It is important to consider the receiving device’s input impedance, supply voltage, and isolation availability. Furthermore, the transducer’s response times must be compatible with the system’s sampling rate. In complex environments, it may be useful to select models with multiple or programmable outputs to accommodate different device types and ensure integration without additional hardware modifications.

Initial calibration is performed at the factory using certified reference instruments, but to maintain accuracy, periodic checks are recommended every 12-24 months, depending on the operating environment and the criticality of the application. Some transducers allow field calibration via trimmers or digital interfaces, while others support automatic self-calibration procedures. During verification, it is important to check linearity and compare readings with certified samples. Proper calibration ensures regulatory compliance and the reliability of the data used in control and analysis processes.

Multi-input transducers are particularly useful when you want to reduce the number of installed devices or manage multiple electrical quantities with a single instrument. They allow you to monitor current, voltage, frequency, or temperature in a single module, simplifying wiring and maintenance. Furthermore, programmable models allow you to reconfigure the device based on future needs, adapting to system modifications or new functions required by the automation system. This flexibility makes them ideal for complex systems, industrial retrofits, and evolving SCADA systems.

The choice of a signal transducer depends on several technical factors, including the quantity to be measured, the required measurement range, the type of input signal available (CT, VT, PT100, thermocouples, potentiometers), and the output signal required by the acquisition system (0-20 mA, 4-20 mA, 0-10 V, pulses). Galvanic isolation, accuracy, linearity, and compatibility with PLC or SCADA system inputs must also be considered. For critical applications, it is also important to consider the accuracy class and any compliance with specific IEC or EN standards for industrial measurement.

When connecting transducers to current transformers (CTs), voltage transformers (VTs), or shunts, it is essential to ensure the compatibility of the transformation ratios and voltage or current levels. Overall accuracy also depends on the precision of the CTs/VTs used, so it is advisable to choose components with an appropriate class for the application. Furthermore, it is necessary to verify the correct polarity of the connections and the maximum permissible secondary load. Careful design of the interface between transducers and measurement sensors ensures reliable readings and minimizes systematic errors.

Galvanic isolation is essential for ensuring system safety and signal reliability. By electrically separating inputs, outputs, and power supplies, it prevents short circuits, reverse current, and interference between connected circuits. This is particularly important in systems with different reference potentials or devices sensitive to electromagnetic interference. Furthermore, galvanic isolation protects the PLC or SCADA system from accidental power surges and improves signal transmission quality, reducing noise and distortion, especially over long distances or in electrically noisy industrial environments.

To reduce the influence of electromagnetic interference, it is recommended to use internally shielded transducers and properly grounded shielded wiring. Galvanic isolation and the use of integrated EMC filters help minimize interference on inputs and outputs. Proper positioning of signal cables, away from power conductors or high-frequency devices, is also essential to maintaining accuracy. In high-sensitivity systems, the use of standardized signals such as 4-20 mA is preferable because they are less susceptible to degradation than low voltages over long distances.

Transducers intended for industrial use must comply with the main European and international standards relating to electrical safety, electromagnetic compatibility, and measurement accuracy. These include IEC 61010-1 for the safety of measuring devices, IEC 61326-1 for EMC compatibility, and EN 60688, specifically for electrical measurement transducers. Compliance with these standards ensures reliability, safe use, and interoperability with complex control systems. The presence of CE markings and, where required, UL or CSA certifications is an additional guarantee.