Today, industrial automation is  essential to many businesses, reducing or eliminating manual labour and the risk of human error. It is used in a range of industries including oil and gas, mining, cement, food processing, water and waste and HVAC. Industrial automation means integrating smart tools and computers into production lines or processes, to transform manual tasks into automated, hands-off , streamlined operations.

Industrial automation can involve many different systems, which have to pass data and information between them. One such example is where temperature monitoring is part of the process, and the information from the temperature sensor, or thermocouple, has to be passed on to a Programmable Logic Computer (PLC) that controls a manufacturing line or robotic devices.

In this scenario, there is a risk that damage could be caused due to a high voltage signal finding a path to the PLC via the thermocouple. Or that some other form of corruption or noise could cause an inaccurate reading. The solution is signal isolation. A signal isolator prevents a high voltage signal or other corruption reaching the PLC.

Electrical isolation essentially means blocking unwanted signals but allowing the wanted signal to transmit through the circuit. It means electrically separating the signal path of the temperature sensor from the rest of the monitoring system.

Signal isolation ensures a stable and accurate interface between the thermocouple and other devices and is designed to ensure that there is no inaccuracy or damage caused by noise, differences in voltage or electro-magnetic interference.

Signal isolation can be achieved through physical separation, through insulating material, or through isolated signal transmission. ECEFast, one of Australia’s leading suppliers of thermocouples, produces sensors with inbuilt signal isolation.

The benefits of signal isolation

Signal isolation enhances safety and ensures accurate readings for effective process management:

1. Electrical Safety

   Signal isolation separates high-voltage sections from low-voltage ones, protecting users and sensitive electronic components from dangerous voltages.

2. Noise Reduction

   Signal isolation minimises the electrical noise than can interfere with output. Industrial environments often have a lot of electrical noise – generated by motors, switches, or other equipment – which can cause inaccurate or unstable readings. Signal isolation therefore increases the reliability of the temperature sensor output.

3. Preventing Ground Loops

   Ground loops, or earth loops, are formed when a thermocouple is grounded in more than one location – for example, the transmitter is grounded at one location and the controller at another. This causes current flow between the ground points, which in turn can create noise interference, damage and distortion. Internal isolation between the input, output and ground eliminates this problem by breaking the ground loop circuit and allowing the signal to pass through without an electrical connection.

4. Signal Integrity

   In some environments, external influence can distort the output signal from the thermocouple, rendering the reading inaccurate. Examples of external influence include Variable Speed Drives (VSDs) commonly used to control the speed of motors, electromagnetic interference (EMI) or radio-frequency interference (RFI). Signal isolation can eliminate interference and ensure an accurate signal.

5. Versatility and Interfacing

   Integrating temperature sensor output with another system, such as a PLC, is difficult if there are differences in voltage levels or ground potentials. If the signal is isolated, these differences are no longer an issue, offering versatility and ease of integration.

Signal isolation can therefore make significant difference in industries where temperature plays a role in managing quality and safety, and where automation means that signals are passed from thermocouples to a PLC. It helps to ensure that the temperature monitoring process is managed safely, and that data integrity and accuracy is protected.